Stopping in a manual transmission
October 23, 2014 4:52 PM Subscribe
6-speed manual transmission, standard clutch--not "paddle" or "semi-automatic" or "clutchless." Two ways to stop:
1) Use the brakes to brake the car: 5th or 4th or whatever gear you're in, neutral, no downshifting, coast to full stop with car not in gear.
2)Use the clutch/engine to brake the car: 55mph in 5th gear, 45mph in 4th gear, 35mph in 3rd gear, etc., downshifting through the gears to slow the car down, then into neutral--instead of into 2nd--when you're only doing 20mph or something.
I've always done #1. For 25 years, no matter what gear or how fast or the RPM's, I put the car into neutral, then use the brakes to stop. I was taught that downshifting was hard on the engine and the clutch, and that the only time you want to slow down by downshifting is when icy/snowy/slippery road conditions make brakes useless b/c there's not enough traction to keep you from sliding.
Today, I was going like 55mph in 5th gear when I saw a red light up ahead and did my thing:5th gear to neutral, brakes to a full stop. The guy I was driving with-- a coworker that I don't know well enough to know if he or isn't full of shit, but who says he knows " a lot about cars"--told me that I was doing it wrong.
He said that with a manual transmission, you want to downshift through the gears to slow down, then use the brakes to come to a full stop.
I said he was wrong.
Who's right?
1) Use the brakes to brake the car: 5th or 4th or whatever gear you're in, neutral, no downshifting, coast to full stop with car not in gear.
2)Use the clutch/engine to brake the car: 55mph in 5th gear, 45mph in 4th gear, 35mph in 3rd gear, etc., downshifting through the gears to slow the car down, then into neutral--instead of into 2nd--when you're only doing 20mph or something.
I've always done #1. For 25 years, no matter what gear or how fast or the RPM's, I put the car into neutral, then use the brakes to stop. I was taught that downshifting was hard on the engine and the clutch, and that the only time you want to slow down by downshifting is when icy/snowy/slippery road conditions make brakes useless b/c there's not enough traction to keep you from sliding.
Today, I was going like 55mph in 5th gear when I saw a red light up ahead and did my thing:5th gear to neutral, brakes to a full stop. The guy I was driving with-- a coworker that I don't know well enough to know if he or isn't full of shit, but who says he knows " a lot about cars"--told me that I was doing it wrong.
He said that with a manual transmission, you want to downshift through the gears to slow down, then use the brakes to come to a full stop.
I said he was wrong.
Who's right?
#2 involves clutching and declutching 4 times. I've changed throwout bearings and I've changed clutches and personally, I'd much rather change brake pads, which is a 2 beer job on most disc-brake equipped cars, 3 beers if rust is a factor.
posted by ftm at 4:59 PM on October 23, 2014 [16 favorites]
posted by ftm at 4:59 PM on October 23, 2014 [16 favorites]
Depending on stopping distance, I think I would try to gear down to at least third, then brake, put the clutch in, go into neutral and then let it slip into first when I'm slow enough. But I'm still a learner driver, officially. I don't think it's necessary to gear down all the way but going from 5th to a stop seems a bit much.
posted by kinddieserzeit at 5:00 PM on October 23, 2014
posted by kinddieserzeit at 5:00 PM on October 23, 2014
I also have a 6-speed manual and learned on a 5-speed.
I do #1 - coast in whatever gear I was in and/or pop it into neutral to slow down, then brake until I come to a stop (shifting into neutral at some point in here).
My husband comes from a racing background and tends to downshift before going around corners into his intended exit gear, using the downshift as part of his slowdown as well. This is to save brain and hand availability for steering around high-speed racing turns. He also more often coasts-in-gear, shifting to neutral before stopping. But that's still along the #1 approach (and just leaves engine RPM higher for longer - I tend to prefer the gas mileage savings but come from a commuter background).
The weird thing to me is that your coworker is recommending is to continuously downshift - I'll brake in-gear for a while then shift into neutral, but shifting down and having the clutch plates go through all that wear seems really strange to me.
posted by bookdragoness at 5:00 PM on October 23, 2014 [1 favorite]
I do #1 - coast in whatever gear I was in and/or pop it into neutral to slow down, then brake until I come to a stop (shifting into neutral at some point in here).
My husband comes from a racing background and tends to downshift before going around corners into his intended exit gear, using the downshift as part of his slowdown as well. This is to save brain and hand availability for steering around high-speed racing turns. He also more often coasts-in-gear, shifting to neutral before stopping. But that's still along the #1 approach (and just leaves engine RPM higher for longer - I tend to prefer the gas mileage savings but come from a commuter background).
The weird thing to me is that your coworker is recommending is to continuously downshift - I'll brake in-gear for a while then shift into neutral, but shifting down and having the clutch plates go through all that wear seems really strange to me.
posted by bookdragoness at 5:00 PM on October 23, 2014 [1 favorite]
The guys at Car Talk are mostly split. I tried to find the show that they talked about it, but here's a quote from Straight Dope:
Among the more vocal exponents of the don't-downshift school are Tom and Ray Magliozzi, hosts of the radio show Car Talk. These guys admit you should downshift when driving down a long hill; otherwise your brakes heat up so much that the brake fluid boils and you lose your ability to stop the car. But on all other occasions, they argue, downshifting does nothing but wear out your clutch faster. A clutch job is expensive; a brake job is cheap by comparison. The proper way to stop is to rely solely on the brakes. Don't put the car into neutral right away, though. Wait till you get down to 10 or 15 miles per hour or just before the engine starts to lug, then throw in the clutch and shift into second in case you need to accelerate. When you come to a full stop, shift into neutral and release the clutch.posted by General Malaise at 5:01 PM on October 23, 2014 [9 favorites]
Well, you aren't wrong that engine braking (via downshifting and loading the engine) puts more wear on the clutch disk, pressure plate, and throw out bearing. And those parts are harder to replace when they wear out. So you can make a good case that although that method works and does allow you to stop with more control, it does wear out components faster. The one important thing about that method is that, when you use it, you are perfectly suited to accelerate again quickly if you need to. You are in gear, and the engine is in the right range for that gear, so acceleration is just a a matter of jumping on the gas. If you were driving your car in a race, or enjoying a spirited drive in the hills, you'd want to use that method.
On the other hand, shifting into neutral and braking will do what it says on the tin. You will wear out your brakes and associated components more quickly, but they are easier to replace than clutch components. You won't be positioned to just jump on the gas and take off, but that may not be a consideration for exiting a freeway.
Myself, I like the feel of engine braking, and I like being in the right gear and ready to accelerate if necessary, so that's what I do. YMMV, as they say.
posted by mosk at 5:01 PM on October 23, 2014 [5 favorites]
On the other hand, shifting into neutral and braking will do what it says on the tin. You will wear out your brakes and associated components more quickly, but they are easier to replace than clutch components. You won't be positioned to just jump on the gas and take off, but that may not be a consideration for exiting a freeway.
Myself, I like the feel of engine braking, and I like being in the right gear and ready to accelerate if necessary, so that's what I do. YMMV, as they say.
posted by mosk at 5:01 PM on October 23, 2014 [5 favorites]
Engine braking is not only possible but necessary in some situations: on very long descents, for instance, it's a good idea to let the engine take the load of regulating speed, to stop the abrasive brakes getting too hot to function properly. Engines have much more efficient cooling systems than brakes.
The other matter to keep in mind is what you do if you suddenly want to accelerate again without having stopped. If you're decelerating from 5th gear, and you put it in neutral---how do you know which gear to go back into?
posted by Fiasco da Gama at 5:01 PM on October 23, 2014 [1 favorite]
The other matter to keep in mind is what you do if you suddenly want to accelerate again without having stopped. If you're decelerating from 5th gear, and you put it in neutral---how do you know which gear to go back into?
posted by Fiasco da Gama at 5:01 PM on October 23, 2014 [1 favorite]
The other matter to keep in mind is what you do if you suddenly want to accelerate again without having stopped. If you're decelerating from 5th gear, and you put it in neutral---how do you know which gear to go back into?
If you suddenly want to accelerate again and you're slowing down from 5th, you're going to need a gear shift anyway-it's not like punching 5th gear at 20 mph is going to move you anywhere unless you're driving something super overpowered.
Unless you're on a big downhill, method 1) is preferable.
posted by Kwine at 5:08 PM on October 23, 2014
If you suddenly want to accelerate again and you're slowing down from 5th, you're going to need a gear shift anyway-it's not like punching 5th gear at 20 mph is going to move you anywhere unless you're driving something super overpowered.
Unless you're on a big downhill, method 1) is preferable.
posted by Kwine at 5:08 PM on October 23, 2014
A great middle ground is "slow down, shift into neutral, then stop." Downshifting allows you to slow to a lower speed than you would otherwise be able to, but even in fifth gear, there's no reason to switch to neutral at 55mph before applying the brakes.
posted by deanc at 5:08 PM on October 23, 2014
posted by deanc at 5:08 PM on October 23, 2014
You'll only wear on the clutch if you use it shift - in most cars, its not required and with some practice is pretty easy to shift up and down without using it much.
Another reason you should downshift, though, is fuel economy. Modern fuel injected cars will cease to supply fuel to an engine if it is coasting in gear - saving both fuel and (some) wear on the engine, because the momentum of the car is driving the engine and accessories.
If you coast, your engine is idling the whole time, expending fuel.
posted by Pogo_Fuzzybutt at 5:09 PM on October 23, 2014 [1 favorite]
Another reason you should downshift, though, is fuel economy. Modern fuel injected cars will cease to supply fuel to an engine if it is coasting in gear - saving both fuel and (some) wear on the engine, because the momentum of the car is driving the engine and accessories.
If you coast, your engine is idling the whole time, expending fuel.
posted by Pogo_Fuzzybutt at 5:09 PM on October 23, 2014 [1 favorite]
You don't have to put the transmission into neutral; all you have to do is keep the clutch pedal depressed. Putting the transmission into neutral is dangerous two ways: it takes longer, and it means you can't easily apply power in an emergency.
You should leave it in gear when you brake. You should downshift as you slow, even if you keep the clutch depressed, so that you are ready to apply power should you need to. There's no good reason to ever have the transmission in neutral, unless you need to leave it idling with no one in the driver's seat.
posted by Chocolate Pickle at 5:09 PM on October 23, 2014 [5 favorites]
You should leave it in gear when you brake. You should downshift as you slow, even if you keep the clutch depressed, so that you are ready to apply power should you need to. There's no good reason to ever have the transmission in neutral, unless you need to leave it idling with no one in the driver's seat.
posted by Chocolate Pickle at 5:09 PM on October 23, 2014 [5 favorites]
I was taught something similar to Chocolate Pickle. Leave it in gear when braking, engage clutch and change down as you slow, so on an exit ramp it might be fifth to fourth, then brake and clutch/brake and down to second at the appropriate speed which gives you options either to drive on in second at the junction (if it's clear) or stop and go down to first. Never in neutral when in motion: only when at a standstill.
posted by holgate at 5:17 PM on October 23, 2014 [2 favorites]
posted by holgate at 5:17 PM on October 23, 2014 [2 favorites]
Downshift until 2nd gear and complete stop.
Put in 1st and keep clutch depressed and foot on break. Unless its a long stop then put in neutral to release left foot and clutch.
Doing so you will always be ready do take off in the right gear.
I am from a country where automatics are rare and traffic is heavy. Did 20 years at least 70k km manually. Never burned a clutch or had transmission troubles...
posted by Mac-Expert at 5:32 PM on October 23, 2014 [3 favorites]
Put in 1st and keep clutch depressed and foot on break. Unless its a long stop then put in neutral to release left foot and clutch.
Doing so you will always be ready do take off in the right gear.
I am from a country where automatics are rare and traffic is heavy. Did 20 years at least 70k km manually. Never burned a clutch or had transmission troubles...
posted by Mac-Expert at 5:32 PM on October 23, 2014 [3 favorites]
Use the brakes unless you're descending a hill or driving a big rig. Here's the thing that makes your coworker wrong in most cases: your car is probably front wheel drive. This means that only the front wheels are connected to the transmission, and if you engine brake, you're only using two of your wheels (half-ish of your available friction against the ground) to brake. If you're on a corner, or it's wet or icy or oily, or there's some sand or a squirrel or whatever, you're more likely to lose traction & go into a skid during engine braking in a fwd car, because the front wheels are trying to slow you down (and possibly steer) and the back end is just along for the ride. Also you're bypassing any kind of antilock brakes you might have by doing this.
Just use the brakes. thats what they're for. Even if you have all wheel drive, you're bypassing the antilock brakes, and you probably don't know how your center diff is going to react to traction loss on one corner of the vehicle. the antilock brakes are designed to know what to do here.
Also, everything everyone else said. Its way easier and cheaper to replace brake bits than it is to replace transmission bits.
Also, your coworker is kind of a megadork for telling you you're driving wrong. tell him he's passengering wrong and offer to let him demonstrate proper walking.
posted by duckstab at 5:39 PM on October 23, 2014 [12 favorites]
Just use the brakes. thats what they're for. Even if you have all wheel drive, you're bypassing the antilock brakes, and you probably don't know how your center diff is going to react to traction loss on one corner of the vehicle. the antilock brakes are designed to know what to do here.
Also, everything everyone else said. Its way easier and cheaper to replace brake bits than it is to replace transmission bits.
Also, your coworker is kind of a megadork for telling you you're driving wrong. tell him he's passengering wrong and offer to let him demonstrate proper walking.
posted by duckstab at 5:39 PM on October 23, 2014 [12 favorites]
I haven't driven a manual transmission car in a long time, but when I did, and when I rode a motorcycle, I didn't just put the car into neutral and brake, rather, I left the car/bike in gear, lifted my foot/hand from the gas, and began to apply the brake while the engine was still engaged. I would put it into neutral before it began to sputter, but I was never in love with the idea of applying the brake on a vehicle that is rolling along on unchecked momentum.
posted by janey47 at 5:51 PM on October 23, 2014 [1 favorite]
posted by janey47 at 5:51 PM on October 23, 2014 [1 favorite]
All this talk of 'it wears your engine and clutch by using the engine and gears to slow down is total rubbish.
This question comes up a lot. Like. A LOT.
NEVER coast in neutral - the loss of control you have over the car and driveline is far worse than any perceived or imaginary wear on clutches, brakes, wallet, engine or anything else. The car must ALWAYS be in gear unless you are coming to a complete stop (at the kind of speed you'd be able to keep up with on foot).
Use the engine to slow you down by downshifting and engine braking, clutch to a stop. End of. There is no valid argument for the alternative that isn't based on fault engineering knowledge or urban myth.
posted by Brockles at 6:12 PM on October 23, 2014 [18 favorites]
This question comes up a lot. Like. A LOT.
NEVER coast in neutral - the loss of control you have over the car and driveline is far worse than any perceived or imaginary wear on clutches, brakes, wallet, engine or anything else. The car must ALWAYS be in gear unless you are coming to a complete stop (at the kind of speed you'd be able to keep up with on foot).
Use the engine to slow you down by downshifting and engine braking, clutch to a stop. End of. There is no valid argument for the alternative that isn't based on fault engineering knowledge or urban myth.
posted by Brockles at 6:12 PM on October 23, 2014 [18 favorites]
It's worth noting that unless you're braking hard and trying to throw weight around (ie driving the car at the limit) you don't need to be downshifting into the next gear down at the earliest possible time, and you can (say) braked down in 4th and then finish off the engine braking in 2nd when you are slow enough (so miss out 3rd) and things like that. You don't need to hit every gear, but do not coast with the clutch foot down (wears out the thrust bearing) and don't coast in neutral (dynamically bad for control of the driveline).
posted by Brockles at 6:16 PM on October 23, 2014 [10 favorites]
posted by Brockles at 6:16 PM on October 23, 2014 [10 favorites]
Brockles has it correct. No need to ever put the car in neutral unless idling for a prolonged period, like a traffic light. Slow down by coasting with the car in gear, just before the engine starts to lug shift to a lower gear, most of the time you can skip a gear, i.e. shift from 5th to 3rd. In 3rd you can coast until you're almost stopped, then push in the clutch and shift to 1st. I've driven sticks for decades and it's common to go 100,000 miles or more before replacing the clutch. The worst thing you can do to a clutch is rest your foot on the clutch pedal. Even a tiny bit of force will cause clutch slippage. Clutch should be fully in or out, don't spend very much time in between. In fact, other than starting from a dead stop it's easy to drive a modern synchromesh transmission without using the clutch at all.
posted by Grumpy old geek at 6:36 PM on October 23, 2014
posted by Grumpy old geek at 6:36 PM on October 23, 2014
The clutch only wears when the input speed is different than the output speed. When shifting, you're getting your 10-20 kilogram crankshaft to go from like 1800 to 2500 RPM if you don't RPM match. That's nowhere near getting your 1000-2000 kilogram car from 0-6mph (0-1000RPM) every time you start from a stop. Clutch wear is a total bugaboo.
If the control and safety arguments are insufficient, consider this: Energy = mass times velocity squared. So if you at least use engine braking from 60->30, you'll have at least dissipated 3/4 of the energy as hot air rather than worn brakes, probably only shifted once, and maintained full control of your car at higher speeds.
No one says you can't brake while downshifting (in fact, you should do so at least a little).
Finally, whatever you do, don't hold in the clutch for long periods of time.
straw: Automatics purposely stay in gear for some engine braking. Try putting an automatic car in neutral while coasting; every one I've tried has had less drag.
(and Brockles is as right as they were in 2008)
posted by flimflam at 6:40 PM on October 23, 2014 [1 favorite]
If the control and safety arguments are insufficient, consider this: Energy = mass times velocity squared. So if you at least use engine braking from 60->30, you'll have at least dissipated 3/4 of the energy as hot air rather than worn brakes, probably only shifted once, and maintained full control of your car at higher speeds.
No one says you can't brake while downshifting (in fact, you should do so at least a little).
Finally, whatever you do, don't hold in the clutch for long periods of time.
straw: Automatics purposely stay in gear for some engine braking. Try putting an automatic car in neutral while coasting; every one I've tried has had less drag.
(and Brockles is as right as they were in 2008)
posted by flimflam at 6:40 PM on October 23, 2014 [1 favorite]
I put my car into neutral when breaking, but I generally am only going from about 30 mph to zero if that in Chicago traffic. I've learned about what speeds my car changes gear in and pop it into whatever gear I need if the situation changes before I stop because often it does. On the interstate I generally downshift until 3rd gear before going into neutral.
I do put my car in first with my foot on the break and clutch when at a stop just in case I get hit my car decides to fly into traffic I want it to stall.
posted by AlexiaSky at 7:00 PM on October 23, 2014
I do put my car in first with my foot on the break and clutch when at a stop just in case I get hit my car decides to fly into traffic I want it to stall.
posted by AlexiaSky at 7:00 PM on October 23, 2014
The easy answer is that brake pads are much cheaper and easier to replace than clutch parts. The complicated answer has been thoroughly explored by a bunch of great comments before this one.
posted by box at 7:14 PM on October 23, 2014
posted by box at 7:14 PM on October 23, 2014
Brakes are cheaper than clutch/trans/engine.
Plus, if your foot is already on the brake you can more readily emergency stop suddenly.
posted by TheAdamist at 7:26 PM on October 23, 2014
Plus, if your foot is already on the brake you can more readily emergency stop suddenly.
posted by TheAdamist at 7:26 PM on October 23, 2014
Brake pads are cheaper than clutches.
That said: while you're decelerating, if you're in neutral and something goes weird that you want to escape, you now have to select a gear. If you were engine braking, you'd already be in a mostly-appropriate gear.
In conclusion, brakingis a land of contrasts depends upon the situation.
posted by pompomtom at 7:30 PM on October 23, 2014
That said: while you're decelerating, if you're in neutral and something goes weird that you want to escape, you now have to select a gear. If you were engine braking, you'd already be in a mostly-appropriate gear.
In conclusion, braking
posted by pompomtom at 7:30 PM on October 23, 2014
Brake pads are cheaper than clutches!
...a statement that is utterly useless for this discussion without analysis of wear rates caused by the two behaviors.
If using only the brakes causes a 2x increase in frequency of brake replacement while engine braking increases frequency of clutch replacement by 1%, engine braking comes out on top. The cost of the part is only one small component of the analysis that people are trying to do here.
PS: Long-time manual driver here. I've spent far more on brakes over the years than I have on clutches. I mostly engine brake.
posted by toomuchpete at 7:35 PM on October 23, 2014 [4 favorites]
...a statement that is utterly useless for this discussion without analysis of wear rates caused by the two behaviors.
If using only the brakes causes a 2x increase in frequency of brake replacement while engine braking increases frequency of clutch replacement by 1%, engine braking comes out on top. The cost of the part is only one small component of the analysis that people are trying to do here.
PS: Long-time manual driver here. I've spent far more on brakes over the years than I have on clutches. I mostly engine brake.
posted by toomuchpete at 7:35 PM on October 23, 2014 [4 favorites]
The easy answer is that brake pads are much cheaper and easier to replace than clutch parts.
Brakes are cheaper than clutch/trans/engine.
Brake pads are cheaper than clutches.
My god, I wish people would stop repeating this 'justification' like it has any weight whatsoever. It does not. It does not wear your clutch/trans/engine to use engine braking any more than normal driving does. If you think it does, you are wrong. Flat out, 100% wrong.
Brake pads are wear components. So are clutches, but clutches last a hell of a lot longer than brakes do. Yes, a clutch change costs much more than a brake change, but will still need doing far less frequently than a brake pad change even if you use engine braking.
Nobody is suggesting that you ONLY brake with the engine and don't touch the brakes. It is not a matter of one or the other. You should brake, but also use engine braking as a matter of course. It is 'not using engine braking' that is wrong, not which one you choose. Use a little or a lot of engine braking and a matching little or lot of braking depending on how hard or fast you need to decelerate.
posted by Brockles at 7:36 PM on October 23, 2014 [5 favorites]
Brakes are cheaper than clutch/trans/engine.
Brake pads are cheaper than clutches.
My god, I wish people would stop repeating this 'justification' like it has any weight whatsoever. It does not. It does not wear your clutch/trans/engine to use engine braking any more than normal driving does. If you think it does, you are wrong. Flat out, 100% wrong.
Brake pads are wear components. So are clutches, but clutches last a hell of a lot longer than brakes do. Yes, a clutch change costs much more than a brake change, but will still need doing far less frequently than a brake pad change even if you use engine braking.
Nobody is suggesting that you ONLY brake with the engine and don't touch the brakes. It is not a matter of one or the other. You should brake, but also use engine braking as a matter of course. It is 'not using engine braking' that is wrong, not which one you choose. Use a little or a lot of engine braking and a matching little or lot of braking depending on how hard or fast you need to decelerate.
posted by Brockles at 7:36 PM on October 23, 2014 [5 favorites]
I was taught something similar to Chocolate Pickle. Leave it in gear when braking, engage clutch and change down as you slow, so on an exit ramp it might be fifth to fourth, then brake and clutch/brake and down to second at the appropriate speed which gives you options either to drive on in second at the junction (if it's clear) or stop and go down to first. Never in neutral when in motion: only when at a standstill.
Me too; I learned to drive in Boston (yes yes some people will raise an eyebrow at "learning" to "drive" in Boston) and did most of my stick driving in the hillier bits of New England.
posted by rtha at 7:48 PM on October 23, 2014
Me too; I learned to drive in Boston (yes yes some people will raise an eyebrow at "learning" to "drive" in Boston) and did most of my stick driving in the hillier bits of New England.
posted by rtha at 7:48 PM on October 23, 2014
Hey, Brockles, I love your car answers, but I don't want you to throw me under the [manual-transmission] bus!
I might not've been as clear as I could've been--let me remedy that now. I think that the 'brakes are cheaper than clutches' thing is a good rule of thumb, but it is oversimplified for thoughtful drivers. I have a truck and a car, both manual, and I use both engine braking and regular braking as a standard (no pun intended) driving practice. You, OP, should do that too.
posted by box at 7:51 PM on October 23, 2014
I might not've been as clear as I could've been--let me remedy that now. I think that the 'brakes are cheaper than clutches' thing is a good rule of thumb, but it is oversimplified for thoughtful drivers. I have a truck and a car, both manual, and I use both engine braking and regular braking as a standard (no pun intended) driving practice. You, OP, should do that too.
posted by box at 7:51 PM on October 23, 2014
My owners manual agrees with Brockles - use both simultaneously. It actually goes farther to call downshifting solely for that purpose unnecessary and "not recommended."
I use the method above - both until near stall, then clutch in for the last bit.
If I may piggyback: I don't understand the hate for being in neutral. I mean, coasting around in neutral isn't great for being ready to respond, but actually bad for the drive line? Isn't that what double-clutching is, however momentarily?
posted by ctmf at 8:33 PM on October 23, 2014
I use the method above - both until near stall, then clutch in for the last bit.
If I may piggyback: I don't understand the hate for being in neutral. I mean, coasting around in neutral isn't great for being ready to respond, but actually bad for the drive line? Isn't that what double-clutching is, however momentarily?
posted by ctmf at 8:33 PM on October 23, 2014
Here's the other reason that engine braking is preferred: it saves a tiny amount of fuel.
When you push the clutch pedal down and the revs fall to idle, the engine is consuming fuel to maintain that idle.
When you engine brake, you use no fuel. All fuel injected engines cut fuel when revs are higher than, oh, 1200-1500 RPM, and the throttle is closed. When you're engine braking, your engine is literally freewheeling.
posted by TheNewWazoo at 8:37 PM on October 23, 2014 [1 favorite]
When you push the clutch pedal down and the revs fall to idle, the engine is consuming fuel to maintain that idle.
When you engine brake, you use no fuel. All fuel injected engines cut fuel when revs are higher than, oh, 1200-1500 RPM, and the throttle is closed. When you're engine braking, your engine is literally freewheeling.
posted by TheNewWazoo at 8:37 PM on October 23, 2014 [1 favorite]
One issue to keep in mind, whether you go for the engine-brake or regular-brake route, is that you always want to retain the ability to keep moving forward. Shifting into neutral early can limit your ability to start accelerating again.
My preference is to at least work down through the gears, even if I'm keeping the clutch held in and slowing using the brakes, so that if I need to pop the clutch (e.g., to avoid getting rammed by some jackwagon merging in obliviously) I'm at least reasonably prepared to.
Since the transmission is in neutral, there's perhaps some small additional wear to the syncros, and some wear to the clutch springs vs. just dropping into neutral, but I've never seen any ill effects from it in several hundred thousand miles of driving.
posted by Kadin2048 at 10:29 PM on October 23, 2014
My preference is to at least work down through the gears, even if I'm keeping the clutch held in and slowing using the brakes, so that if I need to pop the clutch (e.g., to avoid getting rammed by some jackwagon merging in obliviously) I'm at least reasonably prepared to.
Since the transmission is in neutral, there's perhaps some small additional wear to the syncros, and some wear to the clutch springs vs. just dropping into neutral, but I've never seen any ill effects from it in several hundred thousand miles of driving.
posted by Kadin2048 at 10:29 PM on October 23, 2014
I generally just lift off the throttle and then brake letting the car slow down in whatever gear it is in until it is about to bog. Even in 6th on most cars you can get very slow before having to disengage the transmission. If I have to come to a complete stop I almost always put the car in neutral and then release the clutch just as I come to a stop. If I don't come to a complete stop, as soon as I can anticipate that I need to begin accelerating, I select the correct gear for the speed I am at, usually double-clutching—out of old habit—and accelerate away.
posted by bz at 10:44 PM on October 23, 2014 [1 favorite]
posted by bz at 10:44 PM on October 23, 2014 [1 favorite]
Brockles has it:
NEVER coast in neutral - the loss of control you have over the car and driveline is far worse than any perceived or imaginary wear on clutches, brakes, wallet, engine or anything else. The car must ALWAYS be in gear unless you are coming to a complete stop (at the kind of speed you'd be able to keep up with on foot).
It's not about reducing wear on any components of the car but rather the fact that you have better control of the car when it's in gear. Changing down through the gears is best but staying in say 5th gear until you're almost at a stop is fine. It's actually against the UK Highway Code to do what you're doing - see point 102 here.
posted by neilb449 at 11:02 PM on October 23, 2014 [1 favorite]
NEVER coast in neutral - the loss of control you have over the car and driveline is far worse than any perceived or imaginary wear on clutches, brakes, wallet, engine or anything else. The car must ALWAYS be in gear unless you are coming to a complete stop (at the kind of speed you'd be able to keep up with on foot).
It's not about reducing wear on any components of the car but rather the fact that you have better control of the car when it's in gear. Changing down through the gears is best but staying in say 5th gear until you're almost at a stop is fine. It's actually against the UK Highway Code to do what you're doing - see point 102 here.
posted by neilb449 at 11:02 PM on October 23, 2014 [1 favorite]
staying in say 5th gear until you're almost at a stop is fine.
Yeah that's how I learnt in the UK. Brake while in gear and only put the clutch down right when you're about 10-20mph to stop the engine stalling.
posted by EndsOfInvention at 12:12 AM on October 24, 2014
Yeah that's how I learnt in the UK. Brake while in gear and only put the clutch down right when you're about 10-20mph to stop the engine stalling.
posted by EndsOfInvention at 12:12 AM on October 24, 2014
Indeed, in the UK (where most cars are manual), I was taught the way Brockles said. Your car should never be in neutral while moving: you can depress the clutch to acheive the same effect you want, which gives you much more control if something occurs while you are slowing down. Note that as well, as others are saying, you do not need to hit all the gears on the way down, and it is very easy to stop in third gear.
Doing this also means you can gently slow down for lights and then proceed if they turn green. For fuel economy, you can avoid using the brakes simply by anticipating that you will need to brake earlier, and using the road and gear changes to slow you down. This longer process will, again, mean that you are able to proceed if you find that you no longer have to stop.
posted by Cannon Fodder at 3:01 AM on October 24, 2014 [1 favorite]
Doing this also means you can gently slow down for lights and then proceed if they turn green. For fuel economy, you can avoid using the brakes simply by anticipating that you will need to brake earlier, and using the road and gear changes to slow you down. This longer process will, again, mean that you are able to proceed if you find that you no longer have to stop.
posted by Cannon Fodder at 3:01 AM on October 24, 2014 [1 favorite]
Yep, I brake and depress the clutch at 15-20mph, then change into neutral once I've stopped fully. No point in taking the hands off the wheel when I've got other things to concentrate on*. If I'm not going to stop totally, I'll engage 2nd gear at 20mph while slowing to the pace of the almost stopped traffic ahead, but any more gear changes than that is just making busywork for yourself.
*If nothing else, braking nice and smoothly and stopping in the right place, but e.g. if you're in multiple traffic lanes, people often do last minute lane changes while slowing down.
posted by ambrosen at 3:56 AM on October 24, 2014 [3 favorites]
*If nothing else, braking nice and smoothly and stopping in the right place, but e.g. if you're in multiple traffic lanes, people often do last minute lane changes while slowing down.
posted by ambrosen at 3:56 AM on October 24, 2014 [3 favorites]
let me remedy that now. I think that the 'brakes are cheaper than clutches' thing is a good rule of thumb
I appreciate the sentiment, but that is not a good rule of thumb. It is just plain wrong as a justification (it is not a comparable wear case in any reasonable way so the relative cost is irrelevant).. Sorry, but you're firmly under the bus until you drop that 'rule'... ;)
I mean, coasting around in neutral isn't great for being ready to respond, but actually bad for the drive line? Isn't that what double-clutching is, however momentarily?
Double clutching is only for transmissions that don't have a syncromesh. If you're not driving a farm truck or big rig, then double clutching is completely pointless and does nothing at all.
An unloaded drivetrain allows all the various slack in the system to 'rattle' around. There is always a little bit of play in each component and it is better for the system as a whole to be loaded in one direction or the other. Otherwise they tend to rattle back and forth against each other. That is the mechanical aspect of the problem.
The control aspect is that having all the drivewheels freewheeling is not good for dynamic control. It makes them more prone to brake locking (the momentum of the connected components allows inertia to help with that) and it also makes it harder for the ABS system to control the wheel as it locks because it is a relatively light and unloaded component. So it is easier to lock up under braking and also needs more brake pressure released to 'unlock' it because there is less momentum working with the wheel. ABS reduces this effect, but it is still much easier to control a component with a definite loading direction to work against than one that isn't.
In addition, if the drive system is all unloaded and you *do* need to get into gear and do something then all that slack is going to be taken up with a bang when you engage the clutch at which case it is not at all helpful for you. Not only is it a big *clank* that could damage components (reason enough) but the shock to the tyre contact patch could be enough to break traction when you least want that to happen. In addition, if you DO suddenly need to accelerate again it massively increases your lead time to be able to do that. This is dangerous in several ways, not least because it increases the chance of someone running into the back of you in traffic because it takes you too long to get going again if the traffic flow changes. Changing speed should always be done with preparation and intent to continue driving at any speed on the way down or up. It's good practice that gives you more control and better able to react.
Since the transmission is in neutral, there's perhaps some small additional wear to the syncros, and some wear to the clutch springs vs. just dropping into neutral
There will be no additional wear to the syncros *being* in neutral, but there is a chance of extra wear when you reengage the gear because of the greater disparity between engine, gear shaft and road speed. But if operated correctly there is negligible wear on anything other than wear components either way, which is why it's just not a valid argument (I know you're not making it) that one ie better than the other through servicing cost reasons.
I brake and depress the clutch at 15-20mph, then change into neutral once I've stopped fully.
That's still too fast, though. That puts you sitting with load on your clutch release bearing for maybe 1-3 seconds every single time you stop. More if you are braking gently. The clutch release bearing (the thing that spins whenever your foot is on the clutch at all) is the weakest link in that chain so driving with the minimum time with the foot actually on the clutch is best from a wear perspective. Doing a shift down to third relatively early and braking right down to 5mph before clutching (so maybe 0.5-1 second on the pedal because you should lift your foot again when you are in neutral) will make a significant difference to clutch wear in your case.
In addition, 15-20mph and less is the most likely time for brake locking so the unloaded wheels are more of a safety factor than ever at those speeds.
posted by Brockles at 5:08 AM on October 24, 2014 [8 favorites]
I appreciate the sentiment, but that is not a good rule of thumb. It is just plain wrong as a justification (it is not a comparable wear case in any reasonable way so the relative cost is irrelevant).. Sorry, but you're firmly under the bus until you drop that 'rule'... ;)
I mean, coasting around in neutral isn't great for being ready to respond, but actually bad for the drive line? Isn't that what double-clutching is, however momentarily?
Double clutching is only for transmissions that don't have a syncromesh. If you're not driving a farm truck or big rig, then double clutching is completely pointless and does nothing at all.
An unloaded drivetrain allows all the various slack in the system to 'rattle' around. There is always a little bit of play in each component and it is better for the system as a whole to be loaded in one direction or the other. Otherwise they tend to rattle back and forth against each other. That is the mechanical aspect of the problem.
The control aspect is that having all the drivewheels freewheeling is not good for dynamic control. It makes them more prone to brake locking (the momentum of the connected components allows inertia to help with that) and it also makes it harder for the ABS system to control the wheel as it locks because it is a relatively light and unloaded component. So it is easier to lock up under braking and also needs more brake pressure released to 'unlock' it because there is less momentum working with the wheel. ABS reduces this effect, but it is still much easier to control a component with a definite loading direction to work against than one that isn't.
In addition, if the drive system is all unloaded and you *do* need to get into gear and do something then all that slack is going to be taken up with a bang when you engage the clutch at which case it is not at all helpful for you. Not only is it a big *clank* that could damage components (reason enough) but the shock to the tyre contact patch could be enough to break traction when you least want that to happen. In addition, if you DO suddenly need to accelerate again it massively increases your lead time to be able to do that. This is dangerous in several ways, not least because it increases the chance of someone running into the back of you in traffic because it takes you too long to get going again if the traffic flow changes. Changing speed should always be done with preparation and intent to continue driving at any speed on the way down or up. It's good practice that gives you more control and better able to react.
Since the transmission is in neutral, there's perhaps some small additional wear to the syncros, and some wear to the clutch springs vs. just dropping into neutral
There will be no additional wear to the syncros *being* in neutral, but there is a chance of extra wear when you reengage the gear because of the greater disparity between engine, gear shaft and road speed. But if operated correctly there is negligible wear on anything other than wear components either way, which is why it's just not a valid argument (I know you're not making it) that one ie better than the other through servicing cost reasons.
I brake and depress the clutch at 15-20mph, then change into neutral once I've stopped fully.
That's still too fast, though. That puts you sitting with load on your clutch release bearing for maybe 1-3 seconds every single time you stop. More if you are braking gently. The clutch release bearing (the thing that spins whenever your foot is on the clutch at all) is the weakest link in that chain so driving with the minimum time with the foot actually on the clutch is best from a wear perspective. Doing a shift down to third relatively early and braking right down to 5mph before clutching (so maybe 0.5-1 second on the pedal because you should lift your foot again when you are in neutral) will make a significant difference to clutch wear in your case.
In addition, 15-20mph and less is the most likely time for brake locking so the unloaded wheels are more of a safety factor than ever at those speeds.
posted by Brockles at 5:08 AM on October 24, 2014 [8 favorites]
Mosk and Brockles have it 100 percent. That said, criticizing your driving for anything that isn't a safety issue is a dick move.
posted by Dip Flash at 5:13 AM on October 24, 2014 [3 favorites]
posted by Dip Flash at 5:13 AM on October 24, 2014 [3 favorites]
Brake pads are specifically designed to be regularly, and affordably replaced, even by the car owner. Clutches, while being wear items, are not specifically designed the same. The only time I've used engine/clutch braking is when descending a steep grade.
posted by Thorzdad at 5:30 AM on October 24, 2014
posted by Thorzdad at 5:30 AM on October 24, 2014
I'm trying to imagine a scenario in which you can be going 55 and planning to stop, rather than trying to slow enough to make the green.
That's what I would do ... back when I had stick instead of a horrible horrible smart automatic system that makes me insane.
posted by Lesser Shrew at 5:36 AM on October 24, 2014 [1 favorite]
That's what I would do ... back when I had stick instead of a horrible horrible smart automatic system that makes me insane.
posted by Lesser Shrew at 5:36 AM on October 24, 2014 [1 favorite]
Clutches, while being wear items, are not specifically designed the same.
Correct. They are specifically designed to do a completely different job with a different servicing interval and last a significantly longer time. I'm not sure why you are trying to reword an incorrect perception - engine braking does not significantly increase wear on a clutch, so the relative service costs are completely irrelevant.
Repeating something does not make it true. The entire problem is for some reason the driving public have got it into their heads that engine braking wears things out, which is complete fabrication.
posted by Brockles at 5:40 AM on October 24, 2014 [1 favorite]
Correct. They are specifically designed to do a completely different job with a different servicing interval and last a significantly longer time. I'm not sure why you are trying to reword an incorrect perception - engine braking does not significantly increase wear on a clutch, so the relative service costs are completely irrelevant.
Repeating something does not make it true. The entire problem is for some reason the driving public have got it into their heads that engine braking wears things out, which is complete fabrication.
posted by Brockles at 5:40 AM on October 24, 2014 [1 favorite]
It has occurred to me that there may be a completely different perception of engine braking and how to do it. An interpretation/misunderstanding how to do it *would* produce wear on the clutch.
Possible misinterpretation of engine braking (version 1):
Start to slow down, engage much lower gear and 'drag' the clutch against this lower gear (a reversal of the pulling away technique) to use this drag to slow the car.
THIS is bad. This is wrong. This is not what engine braking is. Anyone saying that this is 'bad for the car' is hereby correct in that it is a terrible technique and bad for the clutch (and also bad for the control of the car dynamically).
Correct engine braking (version 2):
Start to slow down, clutch down, select next gear down, clutch straight back up and foot off it, braking lightly/gently throughout. Repeat next downshift as speed reduces. The foot is off the clutch for the vast majority of the time. The revs rise when the gear is engaged (clutch going up) but probably to 2-4000 rpm depending on how hard you want to slow down. The clutch goes 'down and up' as fast and in the exact same way as a normal upshift, no pausing or dragging the clutch.
So if people think that version 1 is 'engine braking' then the problem is their perception of the technique. Basically, it's wrong. If it is version 2, then there is nothing at all wrong or creating extra wear by using that technique. Version 2 is the correct technique for driving a car. It keeps the drive train (lightly) loaded at all times and the clutch fully engaged for the maximum amount of time. The way to increase the life of your clutch is to keep your foot off the pedal for the greatest amount of time during it's being used - if you hold the clutch mid travel (like during a hill start) then THIS is increased clutch wear. Try to reduce time spent with the clutch fully or partially depressed. The answer is not to stop using it, but to use it correctly.
So, again: The longer you have your foot on the pedal of the clutch, the more you are wearing it (or the release bearing) out. End of. That is the ONLY thing that wears the clutch and some wear is normally as it is what the clutch is designed for. Dragging the clutch or sitting with your foot fully depressed on the clutch is actually *worse* for the clutch and bearing than leaving it in gear. If you are at a stop, put the car in neutral and take your foot off the clutch.
posted by Brockles at 5:58 AM on October 24, 2014 [7 favorites]
Possible misinterpretation of engine braking (version 1):
Start to slow down, engage much lower gear and 'drag' the clutch against this lower gear (a reversal of the pulling away technique) to use this drag to slow the car.
THIS is bad. This is wrong. This is not what engine braking is. Anyone saying that this is 'bad for the car' is hereby correct in that it is a terrible technique and bad for the clutch (and also bad for the control of the car dynamically).
Correct engine braking (version 2):
Start to slow down, clutch down, select next gear down, clutch straight back up and foot off it, braking lightly/gently throughout. Repeat next downshift as speed reduces. The foot is off the clutch for the vast majority of the time. The revs rise when the gear is engaged (clutch going up) but probably to 2-4000 rpm depending on how hard you want to slow down. The clutch goes 'down and up' as fast and in the exact same way as a normal upshift, no pausing or dragging the clutch.
So if people think that version 1 is 'engine braking' then the problem is their perception of the technique. Basically, it's wrong. If it is version 2, then there is nothing at all wrong or creating extra wear by using that technique. Version 2 is the correct technique for driving a car. It keeps the drive train (lightly) loaded at all times and the clutch fully engaged for the maximum amount of time. The way to increase the life of your clutch is to keep your foot off the pedal for the greatest amount of time during it's being used - if you hold the clutch mid travel (like during a hill start) then THIS is increased clutch wear. Try to reduce time spent with the clutch fully or partially depressed. The answer is not to stop using it, but to use it correctly.
So, again: The longer you have your foot on the pedal of the clutch, the more you are wearing it (or the release bearing) out. End of. That is the ONLY thing that wears the clutch and some wear is normally as it is what the clutch is designed for. Dragging the clutch or sitting with your foot fully depressed on the clutch is actually *worse* for the clutch and bearing than leaving it in gear. If you are at a stop, put the car in neutral and take your foot off the clutch.
posted by Brockles at 5:58 AM on October 24, 2014 [7 favorites]
Brockles, of course, is right about everything.
I'd recommend reading the section of your car's owner's manual that deals with operating the manual transmission. Mine says, among other things:
"Never take the car out of gear and coast down a hill. This is extremely hazardous. Always leave the car in gear.
"Don't 'ride' the brakes. This can cause them to overheat and malfunction. Instead, when you are driving down a long hill, slow down and shift to a lower gear. When you do this, engine braking will help slow the car."
The transmission should always be engaged when you are moving, except for that last second or two when you are slowing down to a stop. A little practice will teach you, when slowing down, the latest point at which the clutch needs to be engaged to keep the car from stalling. Learn that, and practice it.
posted by Leatherstocking at 6:05 AM on October 24, 2014
I'd recommend reading the section of your car's owner's manual that deals with operating the manual transmission. Mine says, among other things:
"Never take the car out of gear and coast down a hill. This is extremely hazardous. Always leave the car in gear.
"Don't 'ride' the brakes. This can cause them to overheat and malfunction. Instead, when you are driving down a long hill, slow down and shift to a lower gear. When you do this, engine braking will help slow the car."
The transmission should always be engaged when you are moving, except for that last second or two when you are slowing down to a stop. A little practice will teach you, when slowing down, the latest point at which the clutch needs to be engaged to keep the car from stalling. Learn that, and practice it.
posted by Leatherstocking at 6:05 AM on October 24, 2014
Also, a side note: I've driven manual-transmission cars hundreds of thousands of miles over the past 25 years and have never replaced a clutch. If you are driving properly and not abusing the clutch, it will last a very, very long time, possibly the life of the car. So there's really no comparison with brakes.
posted by Leatherstocking at 6:09 AM on October 24, 2014
posted by Leatherstocking at 6:09 AM on October 24, 2014
I'll amend my comment upthread to add that you should absolutely have the car in gear and the clutch engaged at all times unless you're stopped or shifting. Letting off the gas and decelerating is a normal thing to do. I read "engine braking" as shifting into a lower gear than you would be if you were maintaining speed & avoiding the brakes, instead of just letting off the gas and using the brakes, downshifting as needed to keep the engine at normal cruising revs.
posted by duckstab at 6:13 AM on October 24, 2014
posted by duckstab at 6:13 AM on October 24, 2014
Yep, unfortunately Brockles' Version 1 is what a lot of people think of as engine braking, and is what a minority of people actually do (and it's AWFUL if you're sitting in the passenger seat listening to the engine screaming). I think people were responding to that.
posted by tinkletown at 6:36 AM on October 24, 2014
posted by tinkletown at 6:36 AM on October 24, 2014
you're more likely to lose traction & go into a skid during engine braking in a fwd car, because the front wheels are trying to slow you down (and possibly steer) and the back end is just along for the ride. Also you're bypassing any kind of antilock brakes you might have by doing this.
Although you've moved your position to undo some of the incorrect stuff you were stating above, I have to address this as I missed it first time. You are not 'more likely' to skid or lose traction in a fwd car under engine braking. I can see how you can intellectualise that scenario by considering a case where only one axle being braked could potentially be bad, but it really doesn't stand up to much scrutiny because of the factors that would have to be in place for that to happen and be a problem. If it were a potential problem, then it is a problem for a car braking or a car engine+pedal braking or just engine braking. It'd have to be a drastic loss of road friction and all cases would be adversely affected anyway so it becomes moot.
You are not, even just in pure engine braking (no brakes) *more* likely to lose traction nor go into a skid. Nor are you bypassing anti-lock effects, just the ABS braking components. The momentum in the engine and driveline (front or rear wheel drive) is in itself an anti lock device. Even with no fuel being pumped in, the engine and transmission will want to keep turning just through inertia and so prevent the wheel locking. Also, if you are just engine braking you really aren't decelerating by any significant amount compared to full braking so the scenario you suggest is even more unlikely to even occur.
A front wheel drive car does most of its braking with the front wheels. All cars do, but front wheel drives especially because of the weight distribution of the vehicle. Something like 65-70% of the braking is produced by the front axle. Engine braking is not a severe braking case compared to how much force a braking system can produce so for a given relatively gentle rate of deceleration it makes no real difference if you are braking with the brakes or with the engine in your scenario. Yes, you'd stop actually slowing down a small amount in the engine braking case for the 10 feet it would take before the rear wheels hit the same friction issue during which a small amount of rear brake bias would still be in effect in the braking case, but honestly it is not as much as you think it is. The difference is the length of the wheel base multiplied by about 30% of the braking effort. Which is not very much, because if you were trying to slow the car hard you'd be on the brakes anyway.
If a fwd car that is engine braking loses traction on one or both front wheels then it must be a spot of almost zero traction (the braking force from pure engine braking is not very much, so it would be a very severe loss of grip to break traction at the tyre). The wheel would still be turning, but traction would be lost momentarily. ABS would be of no help in that situation because it only releases brake pressure, without any friction or traction involved it is unable to make the wheel turn again (ie change it from stationary - locked - back to rotating). If there was enough friction to do that, then there is enough friction for engine braking to not be an issue. You may have a situation where the wheel turns slightly slower than the road for a fraction of a second, but that is precisely what abs at limit does anyway, so no problems there. With that little friction, then the car won't steer anyway so it will just continue on its path of the momentum in both case. No change.
Losing traction at the front of the car by sudden drop in friction of that order of magnitude would have to mean something of the same loss of friction as black ice. In which case it doesn't matter if you are in full braking or combination engine braking or just engine braking, you're going to slide no matter what.
posted by Brockles at 6:39 AM on October 24, 2014 [2 favorites]
Although you've moved your position to undo some of the incorrect stuff you were stating above, I have to address this as I missed it first time. You are not 'more likely' to skid or lose traction in a fwd car under engine braking. I can see how you can intellectualise that scenario by considering a case where only one axle being braked could potentially be bad, but it really doesn't stand up to much scrutiny because of the factors that would have to be in place for that to happen and be a problem. If it were a potential problem, then it is a problem for a car braking or a car engine+pedal braking or just engine braking. It'd have to be a drastic loss of road friction and all cases would be adversely affected anyway so it becomes moot.
You are not, even just in pure engine braking (no brakes) *more* likely to lose traction nor go into a skid. Nor are you bypassing anti-lock effects, just the ABS braking components. The momentum in the engine and driveline (front or rear wheel drive) is in itself an anti lock device. Even with no fuel being pumped in, the engine and transmission will want to keep turning just through inertia and so prevent the wheel locking. Also, if you are just engine braking you really aren't decelerating by any significant amount compared to full braking so the scenario you suggest is even more unlikely to even occur.
A front wheel drive car does most of its braking with the front wheels. All cars do, but front wheel drives especially because of the weight distribution of the vehicle. Something like 65-70% of the braking is produced by the front axle. Engine braking is not a severe braking case compared to how much force a braking system can produce so for a given relatively gentle rate of deceleration it makes no real difference if you are braking with the brakes or with the engine in your scenario. Yes, you'd stop actually slowing down a small amount in the engine braking case for the 10 feet it would take before the rear wheels hit the same friction issue during which a small amount of rear brake bias would still be in effect in the braking case, but honestly it is not as much as you think it is. The difference is the length of the wheel base multiplied by about 30% of the braking effort. Which is not very much, because if you were trying to slow the car hard you'd be on the brakes anyway.
If a fwd car that is engine braking loses traction on one or both front wheels then it must be a spot of almost zero traction (the braking force from pure engine braking is not very much, so it would be a very severe loss of grip to break traction at the tyre). The wheel would still be turning, but traction would be lost momentarily. ABS would be of no help in that situation because it only releases brake pressure, without any friction or traction involved it is unable to make the wheel turn again (ie change it from stationary - locked - back to rotating). If there was enough friction to do that, then there is enough friction for engine braking to not be an issue. You may have a situation where the wheel turns slightly slower than the road for a fraction of a second, but that is precisely what abs at limit does anyway, so no problems there. With that little friction, then the car won't steer anyway so it will just continue on its path of the momentum in both case. No change.
Losing traction at the front of the car by sudden drop in friction of that order of magnitude would have to mean something of the same loss of friction as black ice. In which case it doesn't matter if you are in full braking or combination engine braking or just engine braking, you're going to slide no matter what.
posted by Brockles at 6:39 AM on October 24, 2014 [2 favorites]
Your friend is a knowitall. As this thread proves, it's not clear which way is "better" (for varying definitions of "goodness"), and it's definitely clear that braking with the brake peddle is fine.
posted by IAmBroom at 8:59 AM on October 24, 2014
posted by IAmBroom at 8:59 AM on October 24, 2014
I think one big perception problem with regard to 'engine braking' is that for a very long time, typical passenger cars didn't have enough gears (i.e. the ratios were too 'tall') to engine brake smoothly without racing the engine.
E.g. if you learned to drive in the "four on the floor" era, then you probably think that using the engine to slow down from highway speeds is a stupid idea, because each gear change is going to cause the engine to rev hard, and the car to undergo a lot of abrupt deceleration (which would be bad on wet / icy / snowy pavement).
However, big trucks do engine braking all the time. They have enough gears that they can downshift sequentially through them, and each gear transition is short enough that letting the clutch out (without riding it) doesn't produce a jerky movement or rev the engine too hard. And in a truck it's important to do this because riding the brakes can cause them to fail (overheat/fade, or run out of air if it's an airbrake system, etc.).
I would argue that in a modern car with a six-speed manual, or even some five-speeds, you can now do the proper truck-style engine braking if you want to. The gear ratios are short enough. Doesn't mean you have to, and I'm not sure it's really any better/worse than using the regular old thermal brakes, though. The braking systems on a car are so overbuilt for the weight of the vehicle, relative to a large truck, that you can ride the hell out of them and you're unlikely to experience true fade unless you're on a racetrack.
Do whichever method you're most comfortable with and prefer.
posted by Kadin2048 at 9:16 AM on October 24, 2014
E.g. if you learned to drive in the "four on the floor" era, then you probably think that using the engine to slow down from highway speeds is a stupid idea, because each gear change is going to cause the engine to rev hard, and the car to undergo a lot of abrupt deceleration (which would be bad on wet / icy / snowy pavement).
However, big trucks do engine braking all the time. They have enough gears that they can downshift sequentially through them, and each gear transition is short enough that letting the clutch out (without riding it) doesn't produce a jerky movement or rev the engine too hard. And in a truck it's important to do this because riding the brakes can cause them to fail (overheat/fade, or run out of air if it's an airbrake system, etc.).
I would argue that in a modern car with a six-speed manual, or even some five-speeds, you can now do the proper truck-style engine braking if you want to. The gear ratios are short enough. Doesn't mean you have to, and I'm not sure it's really any better/worse than using the regular old thermal brakes, though. The braking systems on a car are so overbuilt for the weight of the vehicle, relative to a large truck, that you can ride the hell out of them and you're unlikely to experience true fade unless you're on a racetrack.
Do whichever method you're most comfortable with and prefer.
posted by Kadin2048 at 9:16 AM on October 24, 2014
The simplest thing to do and best for the average driver is just what the Car Talk guys said. Take your foot off the gas, leave it in the current gear and use your brakes to stop. When the engine starts to lug, shift into neutral. That's all there is to it. If you like you can shift into second when at low speed, but it isn't necessary. If you want to pretend you are driving F1, fine bang through all the gears, but it isn't necessary and can even be unsafe for the average driver.
An unloaded drivetrain allows all the various slack in the system to 'rattle' around. There is always a little bit of play in each component and it is better for the system as a whole to be loaded in one direction or the other. Otherwise they tend to rattle back and forth against each other. That is the mechanical aspect of the problem ...if the drive system is all unloaded and you *do* need to get into gear and do something then all that slack is going to be taken up with a bang when you engage the clutch at which case it is not at all helpful for you.
This is just nonsense. There's no damage being done by the system "rattling around." If the drivetrain is loaded, there is no rattling. If there is "rattling" (huh, what?) then the drivetrain is unloaded. The "rattling" can do no harm. You can't have it both ways.
Not only is it a big *clank* that could damage components (reason enough) but the shock to the tyre contact patch could be enough to break traction when you least want that to happen.
This also makes no sense. Going from engine braking to acceleration is more of a *clank* than going from unloaded to acceleration. That's just simple physics. You go from loaded in one direction to loaded in the opposite direction. That is a greater and more abrupt transition in force. Not that I think that this is a factor to worry about anyway, but this explanation in nonsensical.
In addition, 15-20mph and less is the most likely time for brake locking so the unloaded wheels are more of a safety factor than ever at those speeds.
This is also wrong. Any time you are using engine braking instead of your brakes you are defeating the ABS system. That doesn't mean you should coast in neutral -- just the opposite. Engine braking saves your brakes. But the explanation above makes no sense. Engine braking does not help you maintain control of the car for average drivers. That's what your brakes are for.
You are not, even just in pure engine braking (no brakes) *more* likely to lose traction nor go into a skid.
This also false. Dangerously false. Under icy conditions downshifting can definitely put you into an uncontrolled skid. I have tested and done this in both front and rear wheel drive cars. Just a simple downshift, especially the one recommended above (clutch straight back up and foot off it) can put you into a 360 spin. Your ABS can't help you. You may never know when the road is dangerously icy so being in the habit of aggressive downshifting can cause a skid that takes you by surprise. The safer technique for the average driver is to leave the transmission in the same gear, using your brakes to slow down. The ABS will help prevent skidding. ABS cannot help you if you are using pure engine braking. So for the average driver, being in the habit of downshifting every time you slow down is unnecessary but also unsafe.
The simple answer is don't worry about downshifting. Leave the transmission in gear. Use your brakes to slow down. That is what they are for. When the engine starts to lug, shift into neutral or maybe second gear. This is exactly what an automatic transmission car does and that is perfectly safe for the average driver.
posted by JackFlash at 9:27 AM on October 24, 2014 [1 favorite]
An unloaded drivetrain allows all the various slack in the system to 'rattle' around. There is always a little bit of play in each component and it is better for the system as a whole to be loaded in one direction or the other. Otherwise they tend to rattle back and forth against each other. That is the mechanical aspect of the problem ...if the drive system is all unloaded and you *do* need to get into gear and do something then all that slack is going to be taken up with a bang when you engage the clutch at which case it is not at all helpful for you.
This is just nonsense. There's no damage being done by the system "rattling around." If the drivetrain is loaded, there is no rattling. If there is "rattling" (huh, what?) then the drivetrain is unloaded. The "rattling" can do no harm. You can't have it both ways.
Not only is it a big *clank* that could damage components (reason enough) but the shock to the tyre contact patch could be enough to break traction when you least want that to happen.
This also makes no sense. Going from engine braking to acceleration is more of a *clank* than going from unloaded to acceleration. That's just simple physics. You go from loaded in one direction to loaded in the opposite direction. That is a greater and more abrupt transition in force. Not that I think that this is a factor to worry about anyway, but this explanation in nonsensical.
In addition, 15-20mph and less is the most likely time for brake locking so the unloaded wheels are more of a safety factor than ever at those speeds.
This is also wrong. Any time you are using engine braking instead of your brakes you are defeating the ABS system. That doesn't mean you should coast in neutral -- just the opposite. Engine braking saves your brakes. But the explanation above makes no sense. Engine braking does not help you maintain control of the car for average drivers. That's what your brakes are for.
You are not, even just in pure engine braking (no brakes) *more* likely to lose traction nor go into a skid.
This also false. Dangerously false. Under icy conditions downshifting can definitely put you into an uncontrolled skid. I have tested and done this in both front and rear wheel drive cars. Just a simple downshift, especially the one recommended above (clutch straight back up and foot off it) can put you into a 360 spin. Your ABS can't help you. You may never know when the road is dangerously icy so being in the habit of aggressive downshifting can cause a skid that takes you by surprise. The safer technique for the average driver is to leave the transmission in the same gear, using your brakes to slow down. The ABS will help prevent skidding. ABS cannot help you if you are using pure engine braking. So for the average driver, being in the habit of downshifting every time you slow down is unnecessary but also unsafe.
The simple answer is don't worry about downshifting. Leave the transmission in gear. Use your brakes to slow down. That is what they are for. When the engine starts to lug, shift into neutral or maybe second gear. This is exactly what an automatic transmission car does and that is perfectly safe for the average driver.
posted by JackFlash at 9:27 AM on October 24, 2014 [1 favorite]
There seems to be a continued misunderstanding among the 'dont' engine brake' crowd and the engine braking crowd.
1: Engine braking is when you are slowing down and the gear is engaged and the clutch is up. Whatever revs the engine is doing, this is engine braking. If the revs are screaming and high this is severe (and possibly dumb and inappropriate for the road) engine braking, if the engine revs are just above idle, this is just 'not very effective engine braking'. There is a host of differing engine braking loads between those two points.
2: If the car is in neutral the entire time the car is slowing or the clutch is fully down the whole time - this is 'not using engine braking'.
The people who insist (incorrectly) that engine braking is wrong seem to be ONLY considering 'engine braking' as the 'screaming engine braking' dumb engine braking case (or the racing driver case) where you shift down a gear as soon as physically possible, revving the engine near to the red line and producing a big lurch in the car and possibly locking the drive wheels if you do it improperly. That is NOT all that engine braking is.
If you want to pretend you are driving F1, fine bang through all the gears, but it isn't necessary and can even be unsafe for the average driver.
A perfect example of someone completely misunderstanding what engine braking is. It's just braking with the transmission reengaged and the throttle closed, using the natural drag of the engine to assist the brakes.
The simplest thing to do and best for the average driver is just what the Car Talk guys said. Take your foot off the gas, leave it in the current gear and use your brakes to stop.
This is engine braking and brakes together. It is braking with a gentle engine braking component. THIS is what the pro engine braking people are saying to do. During the initial part of lifting off, you can continue the same engine braking component by downshifting to produce a similar relatively gentle engine braking component as you first had when lifting off in the initial gear. It is not a violent or upsetting process to the slowing of the car.
There's no damage being done by the system "rattling around." If the drivetrain is loaded, there is no rattling. If there is "rattling" (huh, what?) then the drivetrain is unloaded. The "rattling" can do no harm.
There is no contradiction. When drive is reengaged (ie the clutch comes up) all the slack will be thrown to the load side at once (not progressively as when you lift off and brake would do) and also the action of engaging the clutch (presumably in a hurry to some extent) will produce a driveline jolt. It just ... does, and can be demonstrated pretty easily - get in a manual car and do it. Drive is taken up when you bring your clutch up in a quicker way than if you lift off the throttle.
Machined components that are unloaded and are clacking back and forth randomly due to their build tolerances can cause damage to a transmission and differential. This is not 'nonsense', this is engineering. It's unlikely to be a major damage by any means, but it is certainly of a similar or larger magnitude than the purported increased clutch wear from engine braking supposedly produces.
You go from loaded in one direction to loaded in the opposite direction. That is a greater and more abrupt transition in force.
The ultimate force? Yes, of course, but the slack and play in the system is gradually taken up during deceleration, not suddenly taken up in the accel direction like when you have to re-engage the gears and let the clutch out. The transition from 'unloaded' to 'accelerating' produces a faster build up of forces in the accel direction. As I said, try it. You'll see for yourself. BUT I'll bet that you modulate the clutch take up automatically when you try it to subconsciously reduce the effect, if you're any kind of experienced driver. This advice is aimed at the inexperienced driver who may just pick a gear, let the clutch out and accelerate all at once. There comes the clank and the potential traction loss.
Any time you are using engine braking instead of your brakes you are defeating the ABS system.
You seem to have fallen into this thought process that it must be one style of braking OR the other. No-one is saying that. In that example you hold up as being false (incorrectly), though, and taking out the erroneous assumption that engine braking precludes using the brake pedal, it is a fact that lower speeds make wheels that are being braked more prone to locking. It is also a fact that wheels with more inertia (ie more components connected to them that are rotating) are less prone to lock up. So at the sub 30-mph speeds, the wheels being braked are more likely to lock if only the brakes are being used than if drive is connected (ie engine braking) while braking.
An ABS system purely releases braking pressure to allow the wheels to rotate at a similar speed during braking. Engine braking is NOT (as I have said repeatedly) a replacement for braking so if you have the brake pedal in play too, the ABS is functioning perfectly well. None of the pro-engine braking people are saying do it instead of the brake pedal, so it doesn't conflict with ABS at all. In fact the inertia of a connected drive system actively helps ABS keep the wheel rotating.
Under icy conditions downshifting can definitely put you into an uncontrolled skid.
Then the way the downshift was completed is the issue, surely? Any severe input' can definitely put you into an uncontrolled skid' in that example, but you seem to be suggesting that the only downshift is a severe downshift. I agree that if a driver isn't capable of a smooth, controlled downshift, then they shouldn't attempt it in slippery conditions. Just as much as if they are incapable of steering without a violent twitch of the wheel, or braking without jumping on the pedal with both feet. Or accelerating at anything less than full throttle. None of which are advisable in slippery conditions and equally so (as I said above). It is the style of the input that is the issue, not the input itself. any severe input in poor conditions can put you in a skid, but a gentle downshift is no more upsetting to the car than gently braking if done correctly. If you are doing 30 mph and you change from (say) 5th to 4th on a slippery road with a relatively gentle clutch action it will NOT suddenly lock your wheels any more than touching the brakes gently or applying the throttle would. It is much more about the gentleness of the action here, you have to compare like for like conditions. Yes, a violent downshift into screaming engine braking will cause you an issue, but a sensibly chosen downshift when grip is present will not cause any more of an issue than touching the brakes will. If it does, it's how you're doing it that is the issue, not a blanket 'don't do that'.
Again, getting off the clutch pedal quickly - that I mention a few times- does not mean banging your foot off it like a racing start, it means a smooth controlled release, but just no clutch slip period. It is not all or nothing with a clutch pedal any more than it is with engine braking itself.
being in the habit of aggressive downshifting can cause a skid that takes you by surprise.
Once more, it seems that the only engine braking people seem to understand is violent engine braking. Nobody but nobody here is advocating 'aggressive downshifting' at all. That is a small element of engine braking that you yourself brought to the discussion and are applying as 'all engine braking'.
posted by Brockles at 10:38 AM on October 24, 2014 [2 favorites]
1: Engine braking is when you are slowing down and the gear is engaged and the clutch is up. Whatever revs the engine is doing, this is engine braking. If the revs are screaming and high this is severe (and possibly dumb and inappropriate for the road) engine braking, if the engine revs are just above idle, this is just 'not very effective engine braking'. There is a host of differing engine braking loads between those two points.
2: If the car is in neutral the entire time the car is slowing or the clutch is fully down the whole time - this is 'not using engine braking'.
The people who insist (incorrectly) that engine braking is wrong seem to be ONLY considering 'engine braking' as the 'screaming engine braking' dumb engine braking case (or the racing driver case) where you shift down a gear as soon as physically possible, revving the engine near to the red line and producing a big lurch in the car and possibly locking the drive wheels if you do it improperly. That is NOT all that engine braking is.
If you want to pretend you are driving F1, fine bang through all the gears, but it isn't necessary and can even be unsafe for the average driver.
A perfect example of someone completely misunderstanding what engine braking is. It's just braking with the transmission reengaged and the throttle closed, using the natural drag of the engine to assist the brakes.
The simplest thing to do and best for the average driver is just what the Car Talk guys said. Take your foot off the gas, leave it in the current gear and use your brakes to stop.
This is engine braking and brakes together. It is braking with a gentle engine braking component. THIS is what the pro engine braking people are saying to do. During the initial part of lifting off, you can continue the same engine braking component by downshifting to produce a similar relatively gentle engine braking component as you first had when lifting off in the initial gear. It is not a violent or upsetting process to the slowing of the car.
There's no damage being done by the system "rattling around." If the drivetrain is loaded, there is no rattling. If there is "rattling" (huh, what?) then the drivetrain is unloaded. The "rattling" can do no harm.
There is no contradiction. When drive is reengaged (ie the clutch comes up) all the slack will be thrown to the load side at once (not progressively as when you lift off and brake would do) and also the action of engaging the clutch (presumably in a hurry to some extent) will produce a driveline jolt. It just ... does, and can be demonstrated pretty easily - get in a manual car and do it. Drive is taken up when you bring your clutch up in a quicker way than if you lift off the throttle.
Machined components that are unloaded and are clacking back and forth randomly due to their build tolerances can cause damage to a transmission and differential. This is not 'nonsense', this is engineering. It's unlikely to be a major damage by any means, but it is certainly of a similar or larger magnitude than the purported increased clutch wear from engine braking supposedly produces.
You go from loaded in one direction to loaded in the opposite direction. That is a greater and more abrupt transition in force.
The ultimate force? Yes, of course, but the slack and play in the system is gradually taken up during deceleration, not suddenly taken up in the accel direction like when you have to re-engage the gears and let the clutch out. The transition from 'unloaded' to 'accelerating' produces a faster build up of forces in the accel direction. As I said, try it. You'll see for yourself. BUT I'll bet that you modulate the clutch take up automatically when you try it to subconsciously reduce the effect, if you're any kind of experienced driver. This advice is aimed at the inexperienced driver who may just pick a gear, let the clutch out and accelerate all at once. There comes the clank and the potential traction loss.
Any time you are using engine braking instead of your brakes you are defeating the ABS system.
You seem to have fallen into this thought process that it must be one style of braking OR the other. No-one is saying that. In that example you hold up as being false (incorrectly), though, and taking out the erroneous assumption that engine braking precludes using the brake pedal, it is a fact that lower speeds make wheels that are being braked more prone to locking. It is also a fact that wheels with more inertia (ie more components connected to them that are rotating) are less prone to lock up. So at the sub 30-mph speeds, the wheels being braked are more likely to lock if only the brakes are being used than if drive is connected (ie engine braking) while braking.
An ABS system purely releases braking pressure to allow the wheels to rotate at a similar speed during braking. Engine braking is NOT (as I have said repeatedly) a replacement for braking so if you have the brake pedal in play too, the ABS is functioning perfectly well. None of the pro-engine braking people are saying do it instead of the brake pedal, so it doesn't conflict with ABS at all. In fact the inertia of a connected drive system actively helps ABS keep the wheel rotating.
Under icy conditions downshifting can definitely put you into an uncontrolled skid.
Then the way the downshift was completed is the issue, surely? Any severe input' can definitely put you into an uncontrolled skid' in that example, but you seem to be suggesting that the only downshift is a severe downshift. I agree that if a driver isn't capable of a smooth, controlled downshift, then they shouldn't attempt it in slippery conditions. Just as much as if they are incapable of steering without a violent twitch of the wheel, or braking without jumping on the pedal with both feet. Or accelerating at anything less than full throttle. None of which are advisable in slippery conditions and equally so (as I said above). It is the style of the input that is the issue, not the input itself. any severe input in poor conditions can put you in a skid, but a gentle downshift is no more upsetting to the car than gently braking if done correctly. If you are doing 30 mph and you change from (say) 5th to 4th on a slippery road with a relatively gentle clutch action it will NOT suddenly lock your wheels any more than touching the brakes gently or applying the throttle would. It is much more about the gentleness of the action here, you have to compare like for like conditions. Yes, a violent downshift into screaming engine braking will cause you an issue, but a sensibly chosen downshift when grip is present will not cause any more of an issue than touching the brakes will. If it does, it's how you're doing it that is the issue, not a blanket 'don't do that'.
Again, getting off the clutch pedal quickly - that I mention a few times- does not mean banging your foot off it like a racing start, it means a smooth controlled release, but just no clutch slip period. It is not all or nothing with a clutch pedal any more than it is with engine braking itself.
being in the habit of aggressive downshifting can cause a skid that takes you by surprise.
Once more, it seems that the only engine braking people seem to understand is violent engine braking. Nobody but nobody here is advocating 'aggressive downshifting' at all. That is a small element of engine braking that you yourself brought to the discussion and are applying as 'all engine braking'.
posted by Brockles at 10:38 AM on October 24, 2014 [2 favorites]
It is also a fact that wheels with more inertia (ie more components connected to them that are rotating) are less prone to lock up.
This is just physics nonsense. Any torque in either direction applied to a wheel, either engine braking or acceleration is more likely to cause loss of traction. The least amount of torque occurs occur either in the highest gear or when freewheeling. It does not occur when you downshift. Engine braking does not increase traction. It's braking -- braking does not increase traction.
It's simply a myth that engine braking increases control of a car. You should use engine braking to save your brakes, not for added control. Mild engine braking by just leaving it in the same gear throughout is just fine. You don't need to downshift when stopping.
You seem to have fallen into this thought process that it must be one style of braking OR the other. No-one is saying that.\
This is what you said "You are not, even just in pure engine braking (no brakes) *more* likely to lose traction nor go into a skid." You are talking about a situation of pure engine braking. In that situation it is simply not true that you are no more likely to skid. In pure engine braking your ABS has no effect and you are more likely to skid. You were making a point about pure engine braking. It is false.
None of the pro-engine braking people are saying do it instead of the brake pedal, so it doesn't conflict with ABS at all.
Okay, so now you are backing up and saying that if, and only if, you coordinate engine braking with the brake pedal, then and only then, will ABS help, but that is not what you said above. So that means you are admitting that a person who does not properly coordinate engine braking and pedal braking is at more risk of skidding. Why should the average driver take more risk? Simple pedal braking is safer. ABS is always in effect. They don't have to coordinate engine braking with pedal braking or risk losing ABS if they do it improperly.
Any severe input' can definitely put you into an uncontrolled skid' in that example, but you seem to be suggesting that the only downshift is a severe downshift. I agree that if a driver isn't capable of a smooth, controlled downshift, then they shouldn't attempt it in slippery conditions.
So now you are waffling again. So under icy conditions one must be more cautious about downshifts unlike your original recommendation "clutch straight back up and foot off it" because that might result in a skid. The point is that the average driver may not do that properly, putting them at risk of a skid. So why recommend something that is totally unnecessary and riskier for the average driver?
There is simply no need to downshift when stopping. Downshifting contributes nothing to your control. Relying on your brakes means that you have full ABS control at all times. If you think you are an above average driver (doesn't everyone) then go ahead and downshift to your heart's delight. But that is a less safe and totally unnecessary recommendation for the average driver.
Simply leave it in the current gear, don't touch the clutch and slow down using your brakes. You will get gentle engine braking in the current gear. No need to downshift. Automatic transmission cars operate this way and are perfectly safe.
posted by JackFlash at 11:38 AM on October 24, 2014
This is just physics nonsense. Any torque in either direction applied to a wheel, either engine braking or acceleration is more likely to cause loss of traction. The least amount of torque occurs occur either in the highest gear or when freewheeling. It does not occur when you downshift. Engine braking does not increase traction. It's braking -- braking does not increase traction.
It's simply a myth that engine braking increases control of a car. You should use engine braking to save your brakes, not for added control. Mild engine braking by just leaving it in the same gear throughout is just fine. You don't need to downshift when stopping.
You seem to have fallen into this thought process that it must be one style of braking OR the other. No-one is saying that.\
This is what you said "You are not, even just in pure engine braking (no brakes) *more* likely to lose traction nor go into a skid." You are talking about a situation of pure engine braking. In that situation it is simply not true that you are no more likely to skid. In pure engine braking your ABS has no effect and you are more likely to skid. You were making a point about pure engine braking. It is false.
None of the pro-engine braking people are saying do it instead of the brake pedal, so it doesn't conflict with ABS at all.
Okay, so now you are backing up and saying that if, and only if, you coordinate engine braking with the brake pedal, then and only then, will ABS help, but that is not what you said above. So that means you are admitting that a person who does not properly coordinate engine braking and pedal braking is at more risk of skidding. Why should the average driver take more risk? Simple pedal braking is safer. ABS is always in effect. They don't have to coordinate engine braking with pedal braking or risk losing ABS if they do it improperly.
Any severe input' can definitely put you into an uncontrolled skid' in that example, but you seem to be suggesting that the only downshift is a severe downshift. I agree that if a driver isn't capable of a smooth, controlled downshift, then they shouldn't attempt it in slippery conditions.
So now you are waffling again. So under icy conditions one must be more cautious about downshifts unlike your original recommendation "clutch straight back up and foot off it" because that might result in a skid. The point is that the average driver may not do that properly, putting them at risk of a skid. So why recommend something that is totally unnecessary and riskier for the average driver?
There is simply no need to downshift when stopping. Downshifting contributes nothing to your control. Relying on your brakes means that you have full ABS control at all times. If you think you are an above average driver (doesn't everyone) then go ahead and downshift to your heart's delight. But that is a less safe and totally unnecessary recommendation for the average driver.
Simply leave it in the current gear, don't touch the clutch and slow down using your brakes. You will get gentle engine braking in the current gear. No need to downshift. Automatic transmission cars operate this way and are perfectly safe.
posted by JackFlash at 11:38 AM on October 24, 2014
Mild engine braking by just leaving it in the same gear throughout is just fine. You don't need to downshift when stopping.
You need to make your mind up. If mild engine braking is fine, why would mild engine braking in the next gear down a bit later suddenly be bad and ruin your ABS system? Consider a 70mph slow down in 5th gear - from 70-55mph you have some engine braking effect that then lessens as the speed drops (and rpm drops). That engine braking effect is 'fine' and all. But it's gone now. Why is it suddenly 'bad' to competently put the car in 4th and get the exact same amount of braking force from 55-40mph as you just used from 70 to 55mph? It's nonsensical that it should suddenly become 'bad'. You may not need it, but you don't *need* to brake at all, really. Just let off the throttle earlier and wait.
But matching the gears to the road speed gives you better ongoing control of the car (for accelerating again, say) and also helps (at the lower rpm) the engine from lugging while keeping the drive connected. Purely this element of being better equipped to drive out of any change of circumstance makes it better, but the additional increase of control over the rotating mass of the car parts means it is more predictable and safer to keep the drive engaged.
AGAIN. Nobody is saying you need to use a LOT of engine braking. But I (and those pro engine braking) ARE saying that engine braking (the drive being connected) is better and safer than freewheeling with neutral selected or with the clutch down. For some reason you seem to be arguing that it is better to have the drive connected (so... engine braking) yet I am still wrong that engine braking is better.
Bizarre.
This is just physics nonsense.
If you don't think that a wheel spinning faster is harder to stop than one spinning slower then you don't get to use 'physics' as an answer. It is not myth, it is basic physics and inertia. To get a wheel to lock the braking force must be greater than the force exerted by the road at the tyre (traction) that keeps it spinning PLUS the inertia of the spinning wheel (or wheel and axle assembly). The more mass you have spinning, or the faster that same mass is spinning, makes the force needed to stop the wheel higher, even with a constant traction/friction coefficient in both cases. Inertia is a function of speed and mass. So for the same speed (wheel spinning at 30mph) it will have more inertia if the mass of the driveline and engine is also spinning with it and connected to it. Basic, basic physics. More inertia means harder to stop spinning/lock that wheel under braking. It is a factor before you even consider the tyre or road surface friction.
Engine braking does not increase traction. It's braking -- braking does not increase traction.
I have no idea how you got to that conclusion. I'm not saying anything of the sort. Nothing like. Traction is not the only thing that dictates whether or not a wheel locks. Having the driveline engaged gives the driven wheels more inertia (more spinning, connected, mass) which has a natural side effect of making that wheel harder to lock for a given braking force and given traction level. Inertia helps the ABS by making it less likely to be triggered on a wheel with a lot of mass spinning with it (the driveline).
It's simply a myth that engine braking increases control of a car.
This is incorrect. It may not be something you are aware of but it throwing out words like 'myth' does not make you right.
You are talking about a situation of pure engine braking.
No, I was trying to address a specific example where someone ELSE was using an example where a car may lose control through pure engine braking. That was one, specific, point I was addressing. I have never said that using engine braking ONLY uses engine braking to slow the car. Stop selectively reading.
now you are backing up and saying that if, and only if, you coordinate engine braking with the brake pedal, then and only then, will ABS help
Nowhere have I said that. I said that using engine braking does not nullify or adversely effect the function of ABS if you are also braking. That's all. You seem to be wilfully missing that particular point, though.
So that means you are admitting that a person who does not properly coordinate engine braking and pedal braking is at more risk of skidding.
No, I am not. Not at all. A bad downshift may make someone skid. So, also would a bad brake pedal application, or a bad throttle application. I am saying that if you do something badly in bad conditions, bad things will happen. That's surely not earth shattering? It's just you weren't allowing for a scenario where there was such a thing as a 'good downshift' and hence saying, essentially, that all downshifts are bad and will cause skidding. This is not true.
The point is that the average driver may not do that properly, putting them at risk of a skid. So why recommend something that is totally unnecessary and riskier for the average driver?
In average conditions with an average driver, downshifting in a sensible and controlled manner is not at all risky. Not in the slightest. No more so than turning the steering wheel. In icy conditions EVERYTHING IS RISKIER. The driver should be more cautious with every aspect of their driving. Why on earth are you using an outlying conditions-based case to try and argue against a standard driving technique. You could just as easily use your logic to say nobody should ever use full throttle because in icy conditions it is risker, and the average driver is not capable of modulating, therefore full throttle is dangerous and unnecessary.
Also, heavy braking in icy conditions is riskier and unnecessary so no driver should use heavy braking. It's not a good technique. Ever. Because it is riskier in icy conditions. It's nonsensical. Icy conditions require a different driving technique than normal conditions. Again, not exactly an earth shattering statement.
Under NORMAL DRIVING CONDITIONS engine braking, in conjunction with normal braking, is a better technique and allows greater control over the car, greater ability to react to changing speed conditions and is a much better technique than disengaging the driveline or holding the clutch down. If you're going to try and quote extreme conditions limitations to that, then you're completely missing the point. In extreme conditions, you don't use normal or average driving, you use extreme weather driving methods. That was NOT THE PREMISE OF THE QUESTION.
There is simply no need to downshift when stopping.
There is really no need to brake when stopping, either, if there is enough room. You can just take your feet off everything and eventually you will come to a stop. That doesn't make using the brakes bad. You'll never lock your wheels coasting to a stop, so that must be better, right?
If you want to stop better and with more control over the car, keep the drive engaged and use engine braking. Don't downshift if you don't want to and so use MORE engine braking, but don't disconnect drive and freewheel-brake. That makes it harder for your ABS to work, not easier.
Downshifting contributes nothing to your control.
This is not true. It has many benefits in suspension control and in allowing the driver to adapt to a change of speed quickly if they are in a roughly appropriate gear at all times. Just because you flat out refuse to believe there are no benefits does not make it so.
Relying on your brakes means that you have full ABS control at all times.
Downshifting and engine braking does absolutely nothing to compromise the effectiveness of the ABS system on the car. Nothing at all. To suggest otherwise is scare mongering.
posted by Brockles at 1:01 PM on October 24, 2014 [4 favorites]
You need to make your mind up. If mild engine braking is fine, why would mild engine braking in the next gear down a bit later suddenly be bad and ruin your ABS system? Consider a 70mph slow down in 5th gear - from 70-55mph you have some engine braking effect that then lessens as the speed drops (and rpm drops). That engine braking effect is 'fine' and all. But it's gone now. Why is it suddenly 'bad' to competently put the car in 4th and get the exact same amount of braking force from 55-40mph as you just used from 70 to 55mph? It's nonsensical that it should suddenly become 'bad'. You may not need it, but you don't *need* to brake at all, really. Just let off the throttle earlier and wait.
But matching the gears to the road speed gives you better ongoing control of the car (for accelerating again, say) and also helps (at the lower rpm) the engine from lugging while keeping the drive connected. Purely this element of being better equipped to drive out of any change of circumstance makes it better, but the additional increase of control over the rotating mass of the car parts means it is more predictable and safer to keep the drive engaged.
AGAIN. Nobody is saying you need to use a LOT of engine braking. But I (and those pro engine braking) ARE saying that engine braking (the drive being connected) is better and safer than freewheeling with neutral selected or with the clutch down. For some reason you seem to be arguing that it is better to have the drive connected (so... engine braking) yet I am still wrong that engine braking is better.
Bizarre.
This is just physics nonsense.
If you don't think that a wheel spinning faster is harder to stop than one spinning slower then you don't get to use 'physics' as an answer. It is not myth, it is basic physics and inertia. To get a wheel to lock the braking force must be greater than the force exerted by the road at the tyre (traction) that keeps it spinning PLUS the inertia of the spinning wheel (or wheel and axle assembly). The more mass you have spinning, or the faster that same mass is spinning, makes the force needed to stop the wheel higher, even with a constant traction/friction coefficient in both cases. Inertia is a function of speed and mass. So for the same speed (wheel spinning at 30mph) it will have more inertia if the mass of the driveline and engine is also spinning with it and connected to it. Basic, basic physics. More inertia means harder to stop spinning/lock that wheel under braking. It is a factor before you even consider the tyre or road surface friction.
Engine braking does not increase traction. It's braking -- braking does not increase traction.
I have no idea how you got to that conclusion. I'm not saying anything of the sort. Nothing like. Traction is not the only thing that dictates whether or not a wheel locks. Having the driveline engaged gives the driven wheels more inertia (more spinning, connected, mass) which has a natural side effect of making that wheel harder to lock for a given braking force and given traction level. Inertia helps the ABS by making it less likely to be triggered on a wheel with a lot of mass spinning with it (the driveline).
It's simply a myth that engine braking increases control of a car.
This is incorrect. It may not be something you are aware of but it throwing out words like 'myth' does not make you right.
You are talking about a situation of pure engine braking.
No, I was trying to address a specific example where someone ELSE was using an example where a car may lose control through pure engine braking. That was one, specific, point I was addressing. I have never said that using engine braking ONLY uses engine braking to slow the car. Stop selectively reading.
now you are backing up and saying that if, and only if, you coordinate engine braking with the brake pedal, then and only then, will ABS help
Nowhere have I said that. I said that using engine braking does not nullify or adversely effect the function of ABS if you are also braking. That's all. You seem to be wilfully missing that particular point, though.
So that means you are admitting that a person who does not properly coordinate engine braking and pedal braking is at more risk of skidding.
No, I am not. Not at all. A bad downshift may make someone skid. So, also would a bad brake pedal application, or a bad throttle application. I am saying that if you do something badly in bad conditions, bad things will happen. That's surely not earth shattering? It's just you weren't allowing for a scenario where there was such a thing as a 'good downshift' and hence saying, essentially, that all downshifts are bad and will cause skidding. This is not true.
The point is that the average driver may not do that properly, putting them at risk of a skid. So why recommend something that is totally unnecessary and riskier for the average driver?
In average conditions with an average driver, downshifting in a sensible and controlled manner is not at all risky. Not in the slightest. No more so than turning the steering wheel. In icy conditions EVERYTHING IS RISKIER. The driver should be more cautious with every aspect of their driving. Why on earth are you using an outlying conditions-based case to try and argue against a standard driving technique. You could just as easily use your logic to say nobody should ever use full throttle because in icy conditions it is risker, and the average driver is not capable of modulating, therefore full throttle is dangerous and unnecessary.
Also, heavy braking in icy conditions is riskier and unnecessary so no driver should use heavy braking. It's not a good technique. Ever. Because it is riskier in icy conditions. It's nonsensical. Icy conditions require a different driving technique than normal conditions. Again, not exactly an earth shattering statement.
Under NORMAL DRIVING CONDITIONS engine braking, in conjunction with normal braking, is a better technique and allows greater control over the car, greater ability to react to changing speed conditions and is a much better technique than disengaging the driveline or holding the clutch down. If you're going to try and quote extreme conditions limitations to that, then you're completely missing the point. In extreme conditions, you don't use normal or average driving, you use extreme weather driving methods. That was NOT THE PREMISE OF THE QUESTION.
There is simply no need to downshift when stopping.
There is really no need to brake when stopping, either, if there is enough room. You can just take your feet off everything and eventually you will come to a stop. That doesn't make using the brakes bad. You'll never lock your wheels coasting to a stop, so that must be better, right?
If you want to stop better and with more control over the car, keep the drive engaged and use engine braking. Don't downshift if you don't want to and so use MORE engine braking, but don't disconnect drive and freewheel-brake. That makes it harder for your ABS to work, not easier.
Downshifting contributes nothing to your control.
This is not true. It has many benefits in suspension control and in allowing the driver to adapt to a change of speed quickly if they are in a roughly appropriate gear at all times. Just because you flat out refuse to believe there are no benefits does not make it so.
Relying on your brakes means that you have full ABS control at all times.
Downshifting and engine braking does absolutely nothing to compromise the effectiveness of the ABS system on the car. Nothing at all. To suggest otherwise is scare mongering.
posted by Brockles at 1:01 PM on October 24, 2014 [4 favorites]
If you don't think that a wheel spinning faster is harder to stop than one spinning slower then you don't get to use 'physics' as an answer.
Wheel inertia and engine braking apply torques in opposite directions. Engine braking torque nullifies the effects of inertia torque on the wheel, making it easier to lock up. If you want to keep the tires from locking up, you don't want to apply engine braking torque.
This is just common sense. The more braking pressure you apply, either by downshifting or pressing the pedal, the more likely you are to skid. In fact, on an icy road, I have initiated a skid by simply taking my foot off the accelerator suddenly. Engine braking is not your friend in icy conditions, so why add more of it than necessary by downshifting. And if you have to make decisions about when it is safe and when it is not safe to use engine braking, then the best rule for the average driver is to minimize it by not downshifting.
Downshifting and engine braking does absolutely nothing to compromise the effectiveness of the ABS system on the car.
This is not true. ABS works by removing braking. If you add engine braking, then you have reduced the effective range of ABS control. You cannot reduce wheel braking to zero. You have less skid protection.
If you do them properly at the same time and modulate the interaction between pedal braking and engine braking on every downshift, everything is fine. Not everyone will do that properly all the time. I think we can both agree that engine braking alone defeats the ABS system. So why complicate it by requiring people to simultaneously apply pedal braking at the same time they downshift. Just forget downshifting completely. Then they can't mess it up.
So my point is that downshifting is unnecessary. Engine braking does not increase control. In fact, under certain conditions is decreases control. It certainly decreases the effectiveness of ABS. So why put an extra burden on the average driver of sussing out these exceptions.
Simply coasting to a stop with the current gear engaged and foot off the clutch is the easiest for the average driver. The less they have to deal with variations in engine braking the better. It is just one more sensory input that people have to integrate with all the other inputs they have to deal with.
There are only two reasons to do engine braking at all. One is that it causes reduces wear on brakes. The other is that it slightly reduces fuel consumption at engine idle. So use the minimal engine braking that has the least adverse effects.
Leave it in the current gear. Control is not compromised. That is what automatic transmission cars do and is perfectly safe.
posted by JackFlash at 2:41 PM on October 24, 2014
Wheel inertia and engine braking apply torques in opposite directions. Engine braking torque nullifies the effects of inertia torque on the wheel, making it easier to lock up. If you want to keep the tires from locking up, you don't want to apply engine braking torque.
This is just common sense. The more braking pressure you apply, either by downshifting or pressing the pedal, the more likely you are to skid. In fact, on an icy road, I have initiated a skid by simply taking my foot off the accelerator suddenly. Engine braking is not your friend in icy conditions, so why add more of it than necessary by downshifting. And if you have to make decisions about when it is safe and when it is not safe to use engine braking, then the best rule for the average driver is to minimize it by not downshifting.
Downshifting and engine braking does absolutely nothing to compromise the effectiveness of the ABS system on the car.
This is not true. ABS works by removing braking. If you add engine braking, then you have reduced the effective range of ABS control. You cannot reduce wheel braking to zero. You have less skid protection.
If you do them properly at the same time and modulate the interaction between pedal braking and engine braking on every downshift, everything is fine. Not everyone will do that properly all the time. I think we can both agree that engine braking alone defeats the ABS system. So why complicate it by requiring people to simultaneously apply pedal braking at the same time they downshift. Just forget downshifting completely. Then they can't mess it up.
So my point is that downshifting is unnecessary. Engine braking does not increase control. In fact, under certain conditions is decreases control. It certainly decreases the effectiveness of ABS. So why put an extra burden on the average driver of sussing out these exceptions.
Simply coasting to a stop with the current gear engaged and foot off the clutch is the easiest for the average driver. The less they have to deal with variations in engine braking the better. It is just one more sensory input that people have to integrate with all the other inputs they have to deal with.
There are only two reasons to do engine braking at all. One is that it causes reduces wear on brakes. The other is that it slightly reduces fuel consumption at engine idle. So use the minimal engine braking that has the least adverse effects.
Leave it in the current gear. Control is not compromised. That is what automatic transmission cars do and is perfectly safe.
posted by JackFlash at 2:41 PM on October 24, 2014
Engine braking torque nullifies the effects of inertia torque on the wheel, making it easier to lock up.
No it doesn't. Engine braking can not make the wheels lock at all but the only adverse effects are if (as mentioned) we are in the 'screaming engine braking' area by dropping into 2nd gear at 50mph (you will lose traction as the wheel is forced to a slower rotation rate than the road speed requires but the wheel will not lock). Gentle to moderate engine braking will do nothing of the sort. Because to stop the wheel you would also have to stop the engine. The engine will itself will prevent that happening as soon as the engine rpm drops below idle by adding fuel to maintain idle speed. So to stop the engine is enormously harder to do than just stopping the wheel. I am staggered that you are unable to comprehend that. Also, connecting the engine (engine braking) ADDS a significant amount of inertia (that of the rotating mass in the engine) to the wheel, not nullifies it. It also provides a self policing barrier to stopping rotating by maintaining idle speed by injecting fuel.
Engine braking force will reduce gradually and stop at or near idle speeds automatically because the engine no longer wants to slow down - the amount of braking effect is proportional to engine speed - down to zero braking effect at or just above engine idle speed. Therefore the driven wheels will not lock up (stop rotating) unless you also stall the engine, which would take significant braking forces. Like, both feet on the pedal huge. You'd have to overcome the ECU, which would be furiously injecting fuel expressly to prevent that happening.
So engine braking cannot - WILL NOT - cause the wheel to stop rotating and lock up. Impossible. However the way engine braking can cause wheels to lose traction is in the absolute worst case of a far, far too early downshift produce a demand to decelerate the engine enough that the wheel loses traction and will turn slightly slower than the road if you are extremely aggressive on your downshift (the aforementioned 50mph in 2nd, or 45mph in first gear) but anything else (so, normal driving) will prevent locking up. The wheel will always still turn, just not necessarily at the same speed as the road requires it to. But this is either at very, very aggressive downshifts in good conditions or by imprudent or clumsy downshifting in poor conditions. Operator error, in other words.
So regardless of the existence of the ABS system, the driveline connected wheels have their own, self contained wheel lock preventing system. Their own additional and supplementary (and so increased) 'skid protection'. The ABS is 'prevented from working' solely because it is entirely redundant for the driven wheels as it is nigh on impossible for them to stop turning anyway while they are connected to the engine. It prevents the ABS being needed on those wheels at all. Which, incidentally, allows it to focus on moderating pressure at the two other wheels more effectively to prevent them locking (the ABS pump has a finite pressure modulation capacity so this is not insignificant).
If you add engine braking, then you have reduced the effective range of ABS control. You cannot reduce wheel braking to zero.
Quite the opposite. Again, your fundamental understanding of the system and the magnitude of the forces involved is flawed. I can see how, again, you have constructed an intellectual argument for this scenario, but the window for reduced effectiveness that you have reasoned is entirely imaginary. Even without engine braking involved at all, you will never need a forced reduction to zero wheel braking force from an ABS system. For you to need a zero braking force to re-rotate the locked wheel then you would need to do so because there was zero friction at the tyre - the braking force is directly balanced against the force trying to keep the wheel turning. If there is zero friction at the tyre it doesn't matter if it is turning or not, does it? Being as ABS systems stop working below about 5mph you'd need to have zero tyre friction of a stopped wheel (therefore zero helping inertia) at greater than 5mph to have a problem which no ABS system will be capable of fixing anyway. Like I said, that's black ice territory. It can't do anything to help the situation. SO even with no engine braking, zero braking force is not a requirement the system needs to allow for, but (as detailed above) the engine prevents the wheels from needing those huge reductions in braking pressure at the brake caliper anyway. The ABS does not need to overcome the engine braking effect like you are imagining.
Remember, for a driven and connected wheel to lock you would have to have stopped the engine. You cannot lock the wheel without stopping the engine so the ABS doesn't even NEED to function for the most part on the driven wheels because the engine effectively does the same job of forcing the wheel to rotate against the engine power. You haven't 'reduced its effectiveness' at all, you've reduced the need for it to be implemented.
It's worth also bearing in mind that if you are braking down to the point where the engine is likely to be at idle rpm during a braking phase then the clutch should be depressed anyway as you're going slow enough. Which is yet one more reason why this magic area of 'reduced ABS effectiveness' doesn't exist.
Leave it in the current gear. Control is not compromised. That is what automatic transmission cars do and is perfectly safe.
Clearly you have your head firmly in the sand, but there seems to be no way I can convince you how wrong you are unless you significantly improve your understanding of how the physics of a car and mechanical system work. Just repeating your assertion based on flawed reasoning and incorrect physics does not make it any more valid.
posted by Brockles at 4:10 PM on October 24, 2014 [4 favorites]
No it doesn't. Engine braking can not make the wheels lock at all but the only adverse effects are if (as mentioned) we are in the 'screaming engine braking' area by dropping into 2nd gear at 50mph (you will lose traction as the wheel is forced to a slower rotation rate than the road speed requires but the wheel will not lock). Gentle to moderate engine braking will do nothing of the sort. Because to stop the wheel you would also have to stop the engine. The engine will itself will prevent that happening as soon as the engine rpm drops below idle by adding fuel to maintain idle speed. So to stop the engine is enormously harder to do than just stopping the wheel. I am staggered that you are unable to comprehend that. Also, connecting the engine (engine braking) ADDS a significant amount of inertia (that of the rotating mass in the engine) to the wheel, not nullifies it. It also provides a self policing barrier to stopping rotating by maintaining idle speed by injecting fuel.
Engine braking force will reduce gradually and stop at or near idle speeds automatically because the engine no longer wants to slow down - the amount of braking effect is proportional to engine speed - down to zero braking effect at or just above engine idle speed. Therefore the driven wheels will not lock up (stop rotating) unless you also stall the engine, which would take significant braking forces. Like, both feet on the pedal huge. You'd have to overcome the ECU, which would be furiously injecting fuel expressly to prevent that happening.
So engine braking cannot - WILL NOT - cause the wheel to stop rotating and lock up. Impossible. However the way engine braking can cause wheels to lose traction is in the absolute worst case of a far, far too early downshift produce a demand to decelerate the engine enough that the wheel loses traction and will turn slightly slower than the road if you are extremely aggressive on your downshift (the aforementioned 50mph in 2nd, or 45mph in first gear) but anything else (so, normal driving) will prevent locking up. The wheel will always still turn, just not necessarily at the same speed as the road requires it to. But this is either at very, very aggressive downshifts in good conditions or by imprudent or clumsy downshifting in poor conditions. Operator error, in other words.
So regardless of the existence of the ABS system, the driveline connected wheels have their own, self contained wheel lock preventing system. Their own additional and supplementary (and so increased) 'skid protection'. The ABS is 'prevented from working' solely because it is entirely redundant for the driven wheels as it is nigh on impossible for them to stop turning anyway while they are connected to the engine. It prevents the ABS being needed on those wheels at all. Which, incidentally, allows it to focus on moderating pressure at the two other wheels more effectively to prevent them locking (the ABS pump has a finite pressure modulation capacity so this is not insignificant).
If you add engine braking, then you have reduced the effective range of ABS control. You cannot reduce wheel braking to zero.
Quite the opposite. Again, your fundamental understanding of the system and the magnitude of the forces involved is flawed. I can see how, again, you have constructed an intellectual argument for this scenario, but the window for reduced effectiveness that you have reasoned is entirely imaginary. Even without engine braking involved at all, you will never need a forced reduction to zero wheel braking force from an ABS system. For you to need a zero braking force to re-rotate the locked wheel then you would need to do so because there was zero friction at the tyre - the braking force is directly balanced against the force trying to keep the wheel turning. If there is zero friction at the tyre it doesn't matter if it is turning or not, does it? Being as ABS systems stop working below about 5mph you'd need to have zero tyre friction of a stopped wheel (therefore zero helping inertia) at greater than 5mph to have a problem which no ABS system will be capable of fixing anyway. Like I said, that's black ice territory. It can't do anything to help the situation. SO even with no engine braking, zero braking force is not a requirement the system needs to allow for, but (as detailed above) the engine prevents the wheels from needing those huge reductions in braking pressure at the brake caliper anyway. The ABS does not need to overcome the engine braking effect like you are imagining.
Remember, for a driven and connected wheel to lock you would have to have stopped the engine. You cannot lock the wheel without stopping the engine so the ABS doesn't even NEED to function for the most part on the driven wheels because the engine effectively does the same job of forcing the wheel to rotate against the engine power. You haven't 'reduced its effectiveness' at all, you've reduced the need for it to be implemented.
It's worth also bearing in mind that if you are braking down to the point where the engine is likely to be at idle rpm during a braking phase then the clutch should be depressed anyway as you're going slow enough. Which is yet one more reason why this magic area of 'reduced ABS effectiveness' doesn't exist.
Leave it in the current gear. Control is not compromised. That is what automatic transmission cars do and is perfectly safe.
Clearly you have your head firmly in the sand, but there seems to be no way I can convince you how wrong you are unless you significantly improve your understanding of how the physics of a car and mechanical system work. Just repeating your assertion based on flawed reasoning and incorrect physics does not make it any more valid.
posted by Brockles at 4:10 PM on October 24, 2014 [4 favorites]
Sorry about the imprecision. I should have said loss of traction, not wheel lock. Loss of traction is what you are really worried about in a skid regardless of wheel lock. Engine braking does not reduce the possibility of loss of traction. It increases it, as does any time you apply the brakes.
Wheel inertia torque and engine braking torque act in opposite directions. Engine braking nullifies the inertia torque that tries to keep the wheel spinning at the same speed. Engine torque slows the turning of the wheel against the inertia of the car. That can induce loss of traction and skidding. That should be perfectly obvious. This isn't rocket science. Stepping on the brake can cause a skid. Engine braking is no different. It can cause a skid. Everyone knows this. It cannot be denied. Many, perhaps most people have experienced this at one time or another. So the idea that engine braking increases control is faulty. Just use your brake pedal.
And engine braking absolutely reduces the effectiveness of ABS. The ABS tries to reduce pedal braking force to prevent wheel slip. Engine braking is trying to do exactly the opposite. Worse, engine braking works on only two of the wheels increasing the asymmetry between front and back braking.
Clearly you have your head firmly in the sand
Yet automatic transmission cars do exactly that. They do not downshift for braking. Are you saying that automatic transmission cars are less safe and lack stability or control?
posted by JackFlash at 4:53 PM on October 24, 2014
Wheel inertia torque and engine braking torque act in opposite directions. Engine braking nullifies the inertia torque that tries to keep the wheel spinning at the same speed. Engine torque slows the turning of the wheel against the inertia of the car. That can induce loss of traction and skidding. That should be perfectly obvious. This isn't rocket science. Stepping on the brake can cause a skid. Engine braking is no different. It can cause a skid. Everyone knows this. It cannot be denied. Many, perhaps most people have experienced this at one time or another. So the idea that engine braking increases control is faulty. Just use your brake pedal.
And engine braking absolutely reduces the effectiveness of ABS. The ABS tries to reduce pedal braking force to prevent wheel slip. Engine braking is trying to do exactly the opposite. Worse, engine braking works on only two of the wheels increasing the asymmetry between front and back braking.
Clearly you have your head firmly in the sand
Yet automatic transmission cars do exactly that. They do not downshift for braking. Are you saying that automatic transmission cars are less safe and lack stability or control?
posted by JackFlash at 4:53 PM on October 24, 2014
And engine braking absolutely reduces the effectiveness of ABS. The ABS tries to reduce pedal braking force to prevent wheel slip. Engine braking is trying to do exactly the opposite.
Total rubbish. Engine braking does NOT do the opposite of ABS. You're in fantasy land now and I cannot even perceive how you came to that conclusion. Engine braking is trying to slow the car. It is not trying to stop the wheels turning. ABS is trying to keep the wheels from turning. No opposites there at all. If you are braking AND engine braking together (as has been repeatedly suggested) ABS will still be able to release pressure on a driven wheel if it under-rotates anyway. Allowing it to rotate at the correct speed. ABS works perfectly well with engine braking.
Worse, engine braking works on only two of the wheels increasing the asymmetry between front and back braking.
If you think that your brakes work equally on all four wheels, then you're in for a shock. That is absolutely not the case. Nor is the asymmetry in your car's braking a problem - it is entirely by design. So you have inherent asymmetry in your brakes anyway - every single time you press the pedal you have asymmetric forces (by design) braking your car. The braking system works on an asymmetric basis and the ABS purely works on relative braking pressure versus wheel speed comparisons. Engine braking does not compromise ABS performance one little bit. You HAVE to have asymmetric braking because the loading on your car (weight distribution front to rear) changes during braking too. Not only is it asymmetric, but it changes the harder you brake, too. All over the place.
Basically - and at the risk of being even more blunt than I typically am - you don't know how car brakes work, nor how ABS works. Nor how engine braking works. Please stop trying to prove a faulty argument based on faulty understanding.
Stepping on the brake can cause a skid. Engine braking is no different.
Correct. In very slippery conditions, this is true. In the kind of conditions that engine braking is problematic, normal braking is also equally problematic. The problematic bit is 'braking in slippery conditions', not which kind of braking you are using. As I say, this is correct. So you're saying they're the essentially the same. Got it. Agreed.
Engine braking nullifies the inertia torque that tries to keep the wheel spinning at the same speed. Engine torque slows the turning of the wheel against the inertia of the car. That can induce loss of traction and skidding.
This is precisely and exactly the same thing that braking does. Because it is .... just braking. So the 'bad thing' you see in engine braking is just... braking. The only difference is that the inertia to keep the wheel spinning in the engine braking case (in conjunction with normal braking, don't forget) is higher than in the brake only scenario (because of the inertia of the engine and gearbox combining with the other rotating mass). So it's better. Less likely to reduce speed quickly and so induce traction loss. Unless you think that inertia doesn't help? Braking forces alone work against less inertia than engine braking does for the same braking force. More inertia, same braking force. More inertia, more stability in the system. Thank you for proving my point.
So the idea that engine braking increases control is faulty. Just use your brake pedal.
But they're no different. You just said so.
They're both a means of slowing the car and you have FINALLY conceded that the only time it is a problem to use it is when it is a problem to use your brakes anyway. It is a gentle method of braking and is no worse than using your brake pedal. It even has natural ABS built in.
So. Use engine braking AND your brake pedal (which is where I came in). Jackflash has finally admitted that they are no worse than each other but has also pointed out that engine braking saves your brake pads so using both is a win-win!
Are you saying that automatic transmission cars are less safe and lack stability or control?
Absolutely. Automatic transmissions do not do that shifting method in order to aid stability of the car, they just do it for smoothness of transmission to the occupants. It does have a compromise (as do most decisions in automotive design for added comfort) and that compromise is in stability.
If you'd like me to demonstrate it (and doubtless scare your pants off at the same time) I can come to a race track of your choice (at your expense) and do hot laps in the same car in full auto and manually shifted mode and show you just how astonishingly unbalanced the car will be in full auto mode under heavy braking and heavy braking+turning. It's really quite scary. I do this (vehicle dynamics) for a living. There is absolutely no question that full auto cars have less control over the chassis under heavy braking (ie emergency situations). Driving it on the track is, of course, not how normal people drive but it is driving at the limit of the car and so analogous to emergency situations. Braking hard for a corner and turning is essentially an emergency manoeuvre. I think you will be very surprised and a little enlightened.
It is no coincidence that a chunk of electronic wizardry has been installed with stability control and the like in modern cars. They need to overcome the inherent stability that they standard systems (including fully auto gearboxes) have introduced into cars as demands have increased for safety from the consumer.
posted by Brockles at 5:36 PM on October 24, 2014 [3 favorites]
Total rubbish. Engine braking does NOT do the opposite of ABS. You're in fantasy land now and I cannot even perceive how you came to that conclusion. Engine braking is trying to slow the car. It is not trying to stop the wheels turning. ABS is trying to keep the wheels from turning. No opposites there at all. If you are braking AND engine braking together (as has been repeatedly suggested) ABS will still be able to release pressure on a driven wheel if it under-rotates anyway. Allowing it to rotate at the correct speed. ABS works perfectly well with engine braking.
Worse, engine braking works on only two of the wheels increasing the asymmetry between front and back braking.
If you think that your brakes work equally on all four wheels, then you're in for a shock. That is absolutely not the case. Nor is the asymmetry in your car's braking a problem - it is entirely by design. So you have inherent asymmetry in your brakes anyway - every single time you press the pedal you have asymmetric forces (by design) braking your car. The braking system works on an asymmetric basis and the ABS purely works on relative braking pressure versus wheel speed comparisons. Engine braking does not compromise ABS performance one little bit. You HAVE to have asymmetric braking because the loading on your car (weight distribution front to rear) changes during braking too. Not only is it asymmetric, but it changes the harder you brake, too. All over the place.
Basically - and at the risk of being even more blunt than I typically am - you don't know how car brakes work, nor how ABS works. Nor how engine braking works. Please stop trying to prove a faulty argument based on faulty understanding.
Stepping on the brake can cause a skid. Engine braking is no different.
Correct. In very slippery conditions, this is true. In the kind of conditions that engine braking is problematic, normal braking is also equally problematic. The problematic bit is 'braking in slippery conditions', not which kind of braking you are using. As I say, this is correct. So you're saying they're the essentially the same. Got it. Agreed.
Engine braking nullifies the inertia torque that tries to keep the wheel spinning at the same speed. Engine torque slows the turning of the wheel against the inertia of the car. That can induce loss of traction and skidding.
This is precisely and exactly the same thing that braking does. Because it is .... just braking. So the 'bad thing' you see in engine braking is just... braking. The only difference is that the inertia to keep the wheel spinning in the engine braking case (in conjunction with normal braking, don't forget) is higher than in the brake only scenario (because of the inertia of the engine and gearbox combining with the other rotating mass). So it's better. Less likely to reduce speed quickly and so induce traction loss. Unless you think that inertia doesn't help? Braking forces alone work against less inertia than engine braking does for the same braking force. More inertia, same braking force. More inertia, more stability in the system. Thank you for proving my point.
So the idea that engine braking increases control is faulty. Just use your brake pedal.
But they're no different. You just said so.
They're both a means of slowing the car and you have FINALLY conceded that the only time it is a problem to use it is when it is a problem to use your brakes anyway. It is a gentle method of braking and is no worse than using your brake pedal. It even has natural ABS built in.
So. Use engine braking AND your brake pedal (which is where I came in). Jackflash has finally admitted that they are no worse than each other but has also pointed out that engine braking saves your brake pads so using both is a win-win!
Are you saying that automatic transmission cars are less safe and lack stability or control?
Absolutely. Automatic transmissions do not do that shifting method in order to aid stability of the car, they just do it for smoothness of transmission to the occupants. It does have a compromise (as do most decisions in automotive design for added comfort) and that compromise is in stability.
If you'd like me to demonstrate it (and doubtless scare your pants off at the same time) I can come to a race track of your choice (at your expense) and do hot laps in the same car in full auto and manually shifted mode and show you just how astonishingly unbalanced the car will be in full auto mode under heavy braking and heavy braking+turning. It's really quite scary. I do this (vehicle dynamics) for a living. There is absolutely no question that full auto cars have less control over the chassis under heavy braking (ie emergency situations). Driving it on the track is, of course, not how normal people drive but it is driving at the limit of the car and so analogous to emergency situations. Braking hard for a corner and turning is essentially an emergency manoeuvre. I think you will be very surprised and a little enlightened.
It is no coincidence that a chunk of electronic wizardry has been installed with stability control and the like in modern cars. They need to overcome the inherent stability that they standard systems (including fully auto gearboxes) have introduced into cars as demands have increased for safety from the consumer.
posted by Brockles at 5:36 PM on October 24, 2014 [3 favorites]
So we agree that there is nothing that engine braking does that pedal braking can't do just as well or better -- four wheels instead of two wheels, full ABS protection, finer control, one braking input to coordinate instead of two. So why should the average driver not on a race track bother with downshifting. You haven't demonstrated a single advantage. And we both agree that if done wrongly, downshifting can get you into trouble with no assistance from ABS to help you out.
So why do it? 94% of U.S. drivers in automatic transmission cars do just fine without downshifting. The average driver in a manual transmission, not on a racetrack, will do just as well by not downshifting.
posted by JackFlash at 8:06 PM on October 24, 2014 [1 favorite]
So why do it? 94% of U.S. drivers in automatic transmission cars do just fine without downshifting. The average driver in a manual transmission, not on a racetrack, will do just as well by not downshifting.
posted by JackFlash at 8:06 PM on October 24, 2014 [1 favorite]
Worth noting that both Jackflash and Brockles do not recommend having the car in neutral all the way down, which is the op's current behaviour.
posted by Cannon Fodder at 6:43 AM on October 25, 2014 [1 favorite]
posted by Cannon Fodder at 6:43 AM on October 25, 2014 [1 favorite]
You seem to have slipped into the 'one or the other' strawman again. Or the 'must use heavy engine braking or it doesn't count' wrong perspective. Allow me to clarify:
Using engine braking while you brake is better, gives you more control, full ABS protection, still only one braking input to control (the pedal) and it gives you greater flexibility for driving out of the braking phase.
YOU said earlier that you were fully supporting and advocating using engine braking when you slow: Simply leave it in the current gear, don't touch the clutch and slow down using your brakes. You will get gentle engine braking in the current gear..
For some reason you seem obsessed with the idea that downshifting to use any more engine braking than that which you already are more than happy to use is OMG DANGEROUS. It is not if used correctly, but you are unconvinced because to you downshifting instantly transforms you into a racing driver in imminent danger of a wild, 360 degree spin. Even if you downshift to maintain the same engine braking force you had a second ago.
Your position is nonsensical. You have agreed that using engine braking by braking in gear is the better option (rather than coasting in neutral, which is 'not using engine braking'). But you seem to have attached all kinds of weird, incorrect bizarreness to the end of that agreement, so good luck to you.
posted by Brockles at 6:49 AM on October 25, 2014 [2 favorites]
Using engine braking while you brake is better, gives you more control, full ABS protection, still only one braking input to control (the pedal) and it gives you greater flexibility for driving out of the braking phase.
YOU said earlier that you were fully supporting and advocating using engine braking when you slow: Simply leave it in the current gear, don't touch the clutch and slow down using your brakes. You will get gentle engine braking in the current gear..
For some reason you seem obsessed with the idea that downshifting to use any more engine braking than that which you already are more than happy to use is OMG DANGEROUS. It is not if used correctly, but you are unconvinced because to you downshifting instantly transforms you into a racing driver in imminent danger of a wild, 360 degree spin. Even if you downshift to maintain the same engine braking force you had a second ago.
Your position is nonsensical. You have agreed that using engine braking by braking in gear is the better option (rather than coasting in neutral, which is 'not using engine braking'). But you seem to have attached all kinds of weird, incorrect bizarreness to the end of that agreement, so good luck to you.
posted by Brockles at 6:49 AM on October 25, 2014 [2 favorites]
Brockles is right. Also, it's better to switch when Monty asks if you want to, and the plane will take off from the treadmill.
Engine braking doesn't put extra wear on anything. This might seem surprising to people who have enough physics to understand that removing kinetic energy from a large moving mass is bound to make it show up as heat somewhere, so let's have a quick look at where that heating actually happens.
If you're on a steep downgrade and you control your speed with the brake pedal, the kinetic energy you're stopping the car from acquiring shows up as heat energy due to friction between brake pads and discs. That friction causes wear to both those components, especially once they're already hot. If you do it for more than a minute or so, you'll know that; the delicate scent of hot brake pads is unmistakable.
If you're on a steep downgrade in a gear low enough to let you control your speed with the accelerator, the engine is being driven by the wheels instead of the other way round. The lower the gear you're in, the faster the engine will rev and the more braking force you'll get from it. But most of the drag you're using is not coming from friction within the engine - it's coming from the difference between ambient atmospheric pressure and the partial vacuum downstream of the mostly-closed throttle. You're putting wear on a "brake pad" made of air, which you're also replacing as you roll.
The only time that engine braking could put any extra wear on your clutch is in the very short periods of rev-matching slip during the actual downshifts. And if clutch wear is a concern for you, the Right Thing is not adopting shitty braking techniques, but conscious practice of rev-matching using the accelerator as you shift. If you habitually achieve quick smooth shifts your passengers can scarcely feel, the clutch ends up doing almost no work.
Flipping into neutral early increases both brake and clutch wear: brake wear because you're asking the brakes to absorb energy that the engine could be diverting if you'd let it, and clutch wear because the lights you're approaching might well turn green again earlier than you thought: rev-matching a previously idling engine to an arbitrary road speed in an arbitrary gear is always going to involve more clutch slip than a set of habit-trained shifts from one gear to the next.
My own braking policy is that any time I have my foot on the brake pedal, I'm wasting both brake pads and fuel: better to have slowed down earlier using gentle engine braking, probably without even needing a gear change, than to have expended the extra fuel needed to get the car to this brakes-requiring speed in the first place. Paying attention to everything in front of the car, not just what the very next car in front of me is doing, makes acting on that policy much easier.
I don't recommend habitual avoidance of all clutch use during shifts. Getting your rev-matching down to the point where you can do a shift that relies totally on synchromesh to get it smooth is all very well, and is certainly a valuable skill to have in case you ever need to limp home in a car with a busted clutch cable, but do it a lot and you will put more wear on the gearbox's internal synchromesh rings than they're designed to deal with.
One last thing: I've never even once seen speedo and tacho readings that would convince me that an automatic transmission I'm driving has gone into neutral as I'm washing off speed with the brake pedal. Ms. flabdablet's AWD auto Subaru certainly doesn't do that. It steps down smoothly through the gears, exactly the way I would under the same conditions in my own little manual Daihatsu.
posted by flabdablet at 8:54 AM on October 25, 2014 [2 favorites]
Engine braking doesn't put extra wear on anything. This might seem surprising to people who have enough physics to understand that removing kinetic energy from a large moving mass is bound to make it show up as heat somewhere, so let's have a quick look at where that heating actually happens.
If you're on a steep downgrade and you control your speed with the brake pedal, the kinetic energy you're stopping the car from acquiring shows up as heat energy due to friction between brake pads and discs. That friction causes wear to both those components, especially once they're already hot. If you do it for more than a minute or so, you'll know that; the delicate scent of hot brake pads is unmistakable.
If you're on a steep downgrade in a gear low enough to let you control your speed with the accelerator, the engine is being driven by the wheels instead of the other way round. The lower the gear you're in, the faster the engine will rev and the more braking force you'll get from it. But most of the drag you're using is not coming from friction within the engine - it's coming from the difference between ambient atmospheric pressure and the partial vacuum downstream of the mostly-closed throttle. You're putting wear on a "brake pad" made of air, which you're also replacing as you roll.
The only time that engine braking could put any extra wear on your clutch is in the very short periods of rev-matching slip during the actual downshifts. And if clutch wear is a concern for you, the Right Thing is not adopting shitty braking techniques, but conscious practice of rev-matching using the accelerator as you shift. If you habitually achieve quick smooth shifts your passengers can scarcely feel, the clutch ends up doing almost no work.
Flipping into neutral early increases both brake and clutch wear: brake wear because you're asking the brakes to absorb energy that the engine could be diverting if you'd let it, and clutch wear because the lights you're approaching might well turn green again earlier than you thought: rev-matching a previously idling engine to an arbitrary road speed in an arbitrary gear is always going to involve more clutch slip than a set of habit-trained shifts from one gear to the next.
My own braking policy is that any time I have my foot on the brake pedal, I'm wasting both brake pads and fuel: better to have slowed down earlier using gentle engine braking, probably without even needing a gear change, than to have expended the extra fuel needed to get the car to this brakes-requiring speed in the first place. Paying attention to everything in front of the car, not just what the very next car in front of me is doing, makes acting on that policy much easier.
I don't recommend habitual avoidance of all clutch use during shifts. Getting your rev-matching down to the point where you can do a shift that relies totally on synchromesh to get it smooth is all very well, and is certainly a valuable skill to have in case you ever need to limp home in a car with a busted clutch cable, but do it a lot and you will put more wear on the gearbox's internal synchromesh rings than they're designed to deal with.
One last thing: I've never even once seen speedo and tacho readings that would convince me that an automatic transmission I'm driving has gone into neutral as I'm washing off speed with the brake pedal. Ms. flabdablet's AWD auto Subaru certainly doesn't do that. It steps down smoothly through the gears, exactly the way I would under the same conditions in my own little manual Daihatsu.
posted by flabdablet at 8:54 AM on October 25, 2014 [2 favorites]
Most automatic transmissions do not downshift through the gears as you slow down. If you watch the tach as you slow down, you won't see a series of jumps in RPM which would indicate downshifts. You may see one gear change as the RPMs get very low to allow a smooth idle, but that is about it. The transmission will generally downshift if you step on the accelerator as you slow, which is an indication that it isn't already in a low gear for optimal engine braking. This is most obvious in CVTs which will immediately drop to about 1200 RPM when you take your foot off the accelerator and stay there the entire time you slow down. They are not using high RPMs for engine braking. They are all using the technique of staying in the current gear as long as possible and downshifting or going into idle as you near a stop. Seems like this simple method would work just as well for the average manual transmission driver. Doesn't mean you can't downshift all you like, just that it isn't necessary for safe operation and simpler for the average driver.
posted by JackFlash at 9:37 AM on October 25, 2014
posted by JackFlash at 9:37 AM on October 25, 2014
Nicer and more modern automatic transmissions work their way down through the gears in order to allow engine braking, as do fancy twin clutch direct shift "automatic" transmissions.
posted by Dip Flash at 9:49 AM on October 25, 2014
posted by Dip Flash at 9:49 AM on October 25, 2014
They are not using high RPMs for engine braking.
This remains the problem. You are incapable of seeing 'engine braking' without also seeing 'high rpms'. You equate 'engine braking' with 'heavy engine braking' and simply not true. Leaving the transmission connected while slowing on zero throttle (or even partial throttle) IS engine braking. It does not require 'high rpms'. It is also still 'engine braking' if you do it with your foot on the brake at the same time.
Most automatic transmissions do not downshift through the gears as you slow down.
Well, older ones don't as much but that is irrelevant. Completely. Older automatic transmissions are not the defining authority on correct gear usage. They are primarily designed and valved/coded for comfort of the occupants, not better vehicle control. They are not very smart components designed for ease of use.
Most automatic transmissions do not downshift through the gears as you slow down.
Of course, more modern automatics (with the greater control of the system available through electronic valve control and GCU's) actually do downshift earlier than traditional (simple pressure based valve block controlled) transmissions did. They also do if you select 'sport' (or equivalent) mode. Sometimes also in towing mode they will downshift earlier to control the car (and towed vehicle) better. They now do this because they are able to provide the extra control without compromising comfort because of the more complex mapping for conditions available through modern electronic control of the gearbox shifting.
Of course, none of this is relevant to anything at all to do with the original question.
They are all using the technique of staying in the current gear as long as possible and downshifting or going into idle as you near a stop.
So they are using engine braking, then. Right. So we're back to square one. So yes, you're AGAIN agreeing with me, but for some reason insisting that what I am saying is wrong? Um...... I am confused.
posted by Brockles at 10:00 AM on October 25, 2014 [3 favorites]
This remains the problem. You are incapable of seeing 'engine braking' without also seeing 'high rpms'. You equate 'engine braking' with 'heavy engine braking' and simply not true. Leaving the transmission connected while slowing on zero throttle (or even partial throttle) IS engine braking. It does not require 'high rpms'. It is also still 'engine braking' if you do it with your foot on the brake at the same time.
Most automatic transmissions do not downshift through the gears as you slow down.
Well, older ones don't as much but that is irrelevant. Completely. Older automatic transmissions are not the defining authority on correct gear usage. They are primarily designed and valved/coded for comfort of the occupants, not better vehicle control. They are not very smart components designed for ease of use.
Most automatic transmissions do not downshift through the gears as you slow down.
Of course, more modern automatics (with the greater control of the system available through electronic valve control and GCU's) actually do downshift earlier than traditional (simple pressure based valve block controlled) transmissions did. They also do if you select 'sport' (or equivalent) mode. Sometimes also in towing mode they will downshift earlier to control the car (and towed vehicle) better. They now do this because they are able to provide the extra control without compromising comfort because of the more complex mapping for conditions available through modern electronic control of the gearbox shifting.
Of course, none of this is relevant to anything at all to do with the original question.
They are all using the technique of staying in the current gear as long as possible and downshifting or going into idle as you near a stop.
So they are using engine braking, then. Right. So we're back to square one. So yes, you're AGAIN agreeing with me, but for some reason insisting that what I am saying is wrong? Um...... I am confused.
posted by Brockles at 10:00 AM on October 25, 2014 [3 favorites]
So they are using engine braking, then. Right. So we're back to square one. So yes, you're AGAIN agreeing with me, but for some reason insisting that what I am saying is wrong? Um...... I am confused.
Perhaps because you aren't listening. Just leave it in the current gear. You will get a small amount of engine braking. It isn't necessary to downshift to get more engine braking. It doesn't make you safer. It doesn't give you more control. If you want to do it, fine. The average driver doesn't need to.
posted by JackFlash at 10:05 AM on October 25, 2014
Perhaps because you aren't listening. Just leave it in the current gear. You will get a small amount of engine braking. It isn't necessary to downshift to get more engine braking. It doesn't make you safer. It doesn't give you more control. If you want to do it, fine. The average driver doesn't need to.
posted by JackFlash at 10:05 AM on October 25, 2014
It isn't 'necessary' to downshift to engine brake. I have never, ever said that. I HAVE said that it is better to use engine braking, which you are agreeing with. You are insisting that I am saying it is necessary to downshift in order to engine brake and that is NOT AT ALL what I have been saying. I'm saying don't disconnect the transmission. YOU are the one that is not listening.
It isn't necessary to downshift to get more engine braking.
Well, it is obviously necessary to downshift to get *more* engine braking, but it is not necessary to always use more engine braking than the car naturally has in the gear you are currently in. I have never suggested otherwise. It can be advantageous in the right circumstances, but not 'necessary'. Never said otherwise.
It is necessary to use your brakes to slow the car to a stop. It is not 'necessary' to stand on the brakes very hard each time.
It is necessary to push the throttle down to accelerate. It is not 'necessary' to use full throttle all the time to accelerate.
Exact same thing. You are trying to equate what I am saying with the extreme usage in your interpretation. Falsely. You are wrong to do so.
It is a better technique to use engine braking when slowing. ON THIS WE ARE AGREED. It gives you more control over the car.
Downshifting does not, in any way, become necessary although neither does it create any safety issues, reductions in control or mythical 'issues' with the ABS system if you choose to do so, though, if done correctly. Downshifting correctly will just give you a greater proportion of engine braking than not downshifting. No extra danger. You are incorrect if you are maintaining that correct usage of downshifting creates any kind of safety issue.
Same as every other thing in a car - if you use it properly it is not dangerous. If you use it incorrectly, it can be.
posted by Brockles at 10:17 AM on October 25, 2014
It isn't necessary to downshift to get more engine braking.
Well, it is obviously necessary to downshift to get *more* engine braking, but it is not necessary to always use more engine braking than the car naturally has in the gear you are currently in. I have never suggested otherwise. It can be advantageous in the right circumstances, but not 'necessary'. Never said otherwise.
It is necessary to use your brakes to slow the car to a stop. It is not 'necessary' to stand on the brakes very hard each time.
It is necessary to push the throttle down to accelerate. It is not 'necessary' to use full throttle all the time to accelerate.
Exact same thing. You are trying to equate what I am saying with the extreme usage in your interpretation. Falsely. You are wrong to do so.
It is a better technique to use engine braking when slowing. ON THIS WE ARE AGREED. It gives you more control over the car.
Downshifting does not, in any way, become necessary although neither does it create any safety issues, reductions in control or mythical 'issues' with the ABS system if you choose to do so, though, if done correctly. Downshifting correctly will just give you a greater proportion of engine braking than not downshifting. No extra danger. You are incorrect if you are maintaining that correct usage of downshifting creates any kind of safety issue.
Same as every other thing in a car - if you use it properly it is not dangerous. If you use it incorrectly, it can be.
posted by Brockles at 10:17 AM on October 25, 2014
Good, then we agree. If you look back this no different from what I said from the very beginning.
Just leave it in the current gear. You will get a small amount of engine braking. It isn't necessary to downshift to get more engine braking. It doesn't make you safer. It doesn't give you more control. If you want to do it, fine. The average driver doesn't need to.
In fact, that is what the Car Talk guys said quoted at the beginning of the thread.
I also agree with you that downshifting, when done improperly under certain conditions, can get you into trouble, which is a second reason I don't recommend unnecessary downshifting for the average driver.
posted by JackFlash at 10:27 AM on October 25, 2014
Just leave it in the current gear. You will get a small amount of engine braking. It isn't necessary to downshift to get more engine braking. It doesn't make you safer. It doesn't give you more control. If you want to do it, fine. The average driver doesn't need to.
In fact, that is what the Car Talk guys said quoted at the beginning of the thread.
I also agree with you that downshifting, when done improperly under certain conditions, can get you into trouble, which is a second reason I don't recommend unnecessary downshifting for the average driver.
posted by JackFlash at 10:27 AM on October 25, 2014
From my second comment in the thread:
You don't need to hit every gear, but do not coast with the clutch foot down (wears out the thrust bearing) and don't coast in neutral (dynamically bad for control of the driveline).
posted by Brockles at 10:50 AM on October 25, 2014
You don't need to hit every gear, but do not coast with the clutch foot down (wears out the thrust bearing) and don't coast in neutral (dynamically bad for control of the driveline).
posted by Brockles at 10:50 AM on October 25, 2014
It isn't necessary to downshift to get more engine braking.
My usual driving style, and the roads I usually drive, mean that most times I slow down I'm doing so at rates achievable easily, safely and smoothly by engine braking alone. And if the engine isn't giving me quite as much deceleration as I'd like, and I want more engine braking, then dropping down one gear is both necessary and appropriate.
I don't recommend unnecessary downshifting for the average driver.
I don't recommend unnecessary use of the brake pedal for any driver.
The use of unnecessary violence in the apprehension of the Blues Brothers has been approved.
posted by flabdablet at 11:08 AM on October 25, 2014 [3 favorites]
My usual driving style, and the roads I usually drive, mean that most times I slow down I'm doing so at rates achievable easily, safely and smoothly by engine braking alone. And if the engine isn't giving me quite as much deceleration as I'd like, and I want more engine braking, then dropping down one gear is both necessary and appropriate.
I don't recommend unnecessary downshifting for the average driver.
I don't recommend unnecessary use of the brake pedal for any driver.
The use of unnecessary violence in the apprehension of the Blues Brothers has been approved.
posted by flabdablet at 11:08 AM on October 25, 2014 [3 favorites]
downshifting, when done improperly under certain conditions, can get you into trouble
Driving improperly under certain conditions can get you into trouble. Learning and practicing sound car control skills makes you less likely to drive improperly in any conditions.
posted by flabdablet at 11:13 AM on October 25, 2014 [1 favorite]
Driving improperly under certain conditions can get you into trouble. Learning and practicing sound car control skills makes you less likely to drive improperly in any conditions.
posted by flabdablet at 11:13 AM on October 25, 2014 [1 favorite]
isn't necessary to downshift to get more engine braking. It doesn't make you safer. It doesn't give you more control.
The control element is about being in a somewhat appropriate gear for your speed at a point where you may need it, and neutral is not appropriate unless your speed is 0mph. (The only time I was taught to put a car in neutral when on the road was at a red light with a pedestrian crossing, with the handbrake engaged, as a belt-and-braces way to avoid accidentally lurching forward.)
If you're suggesting that the average American driver will never be taught how to do this properly, then you may have a point, but in that case, the average American driver is better off sticking with an automatic.
posted by holgate at 11:37 AM on October 25, 2014 [2 favorites]
The control element is about being in a somewhat appropriate gear for your speed at a point where you may need it, and neutral is not appropriate unless your speed is 0mph. (The only time I was taught to put a car in neutral when on the road was at a red light with a pedestrian crossing, with the handbrake engaged, as a belt-and-braces way to avoid accidentally lurching forward.)
If you're suggesting that the average American driver will never be taught how to do this properly, then you may have a point, but in that case, the average American driver is better off sticking with an automatic.
posted by holgate at 11:37 AM on October 25, 2014 [2 favorites]
I want more engine braking, then dropping down one gear is both necessary and appropriate.
It is necessary for your choice of driving style. It is no way necessary for the average driver.
I don't recommend unnecessary use of the brake pedal for any driver.
Again, that is your choice of driving style. The average driver have much finer and more intuitive control of braking effort using the brake pedal than clutching and downshifting.
Driving improperly under certain conditions can get you into trouble.
But why add an unnecessary complication for the average driver? Perhaps you do not frequently drive in black ice conditions, but for the average driver who does, downshifting can cause two-wheel braking with no ABS backup that can result in a spinout. Why take that unnecessary chance? ABS is there for a reason. Drivers make mistakes. For the average driver, simpler is better and safer. Nobody is saying you aren't free to make your own choices.
I share the road with other drivers and my safety depends on their safety. For my own interests I encourage other drivers to use the simplest, safest means of operating their vehicle.
posted by JackFlash at 11:38 AM on October 25, 2014
It is necessary for your choice of driving style. It is no way necessary for the average driver.
I don't recommend unnecessary use of the brake pedal for any driver.
Again, that is your choice of driving style. The average driver have much finer and more intuitive control of braking effort using the brake pedal than clutching and downshifting.
Driving improperly under certain conditions can get you into trouble.
But why add an unnecessary complication for the average driver? Perhaps you do not frequently drive in black ice conditions, but for the average driver who does, downshifting can cause two-wheel braking with no ABS backup that can result in a spinout. Why take that unnecessary chance? ABS is there for a reason. Drivers make mistakes. For the average driver, simpler is better and safer. Nobody is saying you aren't free to make your own choices.
I share the road with other drivers and my safety depends on their safety. For my own interests I encourage other drivers to use the simplest, safest means of operating their vehicle.
posted by JackFlash at 11:38 AM on October 25, 2014
for the average driver who does [drive in black ice conditions], downshifting can cause two-wheel braking with no ABS backup that can result in a spinout.
Driving perfectly normally at 30mph in black ice conditions can cause complete and total loss of control, so I therefore recommend (for my own interests and safety?) the average driver never drive above 20mph. At any time. Ever. Height of summer or depths of winter.
Wait, hang on. That would be ridiculous to demand. (In addition, ABS won't save you in black ice conditions, either, the second all four wheels are on it. Your trust and faith in ABS is not aligned with how effective the system is in reality. So an awful lot of your logic on this is based on fault understanding).
Your argument hinges on the use of a minor edge case condition (one which already dictates a significantly modified driving style in every respect) to attempt to justify ruling out a functional, useful and perfectly good driving technique. This is a ridiculous position to take.
A downshift is not a 'complication' any more than an upshift is. It is just part of operating the vehicle. If it complicates your own driving, then I do recommend you stick to a more simple and basic car as clearly manual gearboxes are outside your skill level.
I encourage other drivers to use the simplest, safest means of operating their vehicle.
The simplest is not always the safest. Right there is the source of your misunderstanding. You believe that anything that complicates (in your mind) how to drive adds a layer of danger. This is not correct. If people are unable to use the gears to control the car at all, they are clearly better suited to being in an automatic car. For drivers who have a modicum of ability there is nothing wrong or difficult with using downshifting as a normal part of driving. Millions of people all over the world are able to downshift their cars while braking without disappearing into a ball of flame and crushed metal. It is not a dangerous - in any way - technique.
It only becomes dangerous if it is beyond the skill or mental capacity of the driver in question, in which case it is that very lack of skill that is the problem, not the technique. Get thee into an auto.
The average driver have much finer and more intuitive control of braking effort using the brake pedal than clutching and downshifting.
You'll need to cite some research to back this kind of claim up because, frankly, this is entirely based on your own personal opinion. As I mention, I work in Vehicle Dynamics for a living and with various levels of drivers from 'normal average people' to professional racing drivers. All are capable of producing a greater and intuitive level of control using the gears AND the brakes to control the car. Just because you can't do it (or just flat out refuse to believe it is possible) does not make your position correct.
I've trained average people to use and feel the positive effects on stability in their own cars many, many times. Don't be so afraid of something you don't understand.
posted by Brockles at 12:01 PM on October 25, 2014 [3 favorites]
Driving perfectly normally at 30mph in black ice conditions can cause complete and total loss of control, so I therefore recommend (for my own interests and safety?) the average driver never drive above 20mph. At any time. Ever. Height of summer or depths of winter.
Wait, hang on. That would be ridiculous to demand. (In addition, ABS won't save you in black ice conditions, either, the second all four wheels are on it. Your trust and faith in ABS is not aligned with how effective the system is in reality. So an awful lot of your logic on this is based on fault understanding).
Your argument hinges on the use of a minor edge case condition (one which already dictates a significantly modified driving style in every respect) to attempt to justify ruling out a functional, useful and perfectly good driving technique. This is a ridiculous position to take.
A downshift is not a 'complication' any more than an upshift is. It is just part of operating the vehicle. If it complicates your own driving, then I do recommend you stick to a more simple and basic car as clearly manual gearboxes are outside your skill level.
I encourage other drivers to use the simplest, safest means of operating their vehicle.
The simplest is not always the safest. Right there is the source of your misunderstanding. You believe that anything that complicates (in your mind) how to drive adds a layer of danger. This is not correct. If people are unable to use the gears to control the car at all, they are clearly better suited to being in an automatic car. For drivers who have a modicum of ability there is nothing wrong or difficult with using downshifting as a normal part of driving. Millions of people all over the world are able to downshift their cars while braking without disappearing into a ball of flame and crushed metal. It is not a dangerous - in any way - technique.
It only becomes dangerous if it is beyond the skill or mental capacity of the driver in question, in which case it is that very lack of skill that is the problem, not the technique. Get thee into an auto.
The average driver have much finer and more intuitive control of braking effort using the brake pedal than clutching and downshifting.
You'll need to cite some research to back this kind of claim up because, frankly, this is entirely based on your own personal opinion. As I mention, I work in Vehicle Dynamics for a living and with various levels of drivers from 'normal average people' to professional racing drivers. All are capable of producing a greater and intuitive level of control using the gears AND the brakes to control the car. Just because you can't do it (or just flat out refuse to believe it is possible) does not make your position correct.
I've trained average people to use and feel the positive effects on stability in their own cars many, many times. Don't be so afraid of something you don't understand.
posted by Brockles at 12:01 PM on October 25, 2014 [3 favorites]
attempt to justify ruling out a functional, useful and perfectly good driving technique.
I have never attempted to rule it out. Do what you like. I'm just saying is it is unnecessary and safer for the average driver.
I've trained average people to use and feel the positive effects on stability in their own cars many, many times.
Which just goes to prove my point. Average drivers don't have that training.
posted by JackFlash at 12:12 PM on October 25, 2014
I have never attempted to rule it out. Do what you like. I'm just saying is it is unnecessary and safer for the average driver.
I've trained average people to use and feel the positive effects on stability in their own cars many, many times.
Which just goes to prove my point. Average drivers don't have that training.
posted by JackFlash at 12:12 PM on October 25, 2014
Mod note: Brockles, JackFlash, I think we've run this debate into the ground a bit and it'd be best to back off and let others chime in if necessary.
posted by mathowie (staff) at 12:16 PM on October 25, 2014
posted by mathowie (staff) at 12:16 PM on October 25, 2014
Average drivers who come to AskMe looking for information on car control are seeking that training.
Obviously it's not likely that any of us will end up sitting next to BadgerDoctor doing that training in person, but providing accurate and reasoned recommendations on sound technique to people specifically looking for it surely counts as a good thing.
Reassuring folks with limited car control ability that bare-minimum skills are appropriate, expected, and sufficient because "average": not so much.
posted by flabdablet at 11:15 PM on October 25, 2014 [6 favorites]
Obviously it's not likely that any of us will end up sitting next to BadgerDoctor doing that training in person, but providing accurate and reasoned recommendations on sound technique to people specifically looking for it surely counts as a good thing.
Reassuring folks with limited car control ability that bare-minimum skills are appropriate, expected, and sufficient because "average": not so much.
posted by flabdablet at 11:15 PM on October 25, 2014 [6 favorites]
I don't recommend unnecessary use of the brake pedal for any driver.
I think we've stumbled into some sort of religious war here that I don't really want to perpetuate, but I think it's worth pointing out that if you ONLY engine-brake, without using the brake pedal at all, you will not trigger your car's brake lights. It may dramatically increase the risk of someone running into you from behind.
So it is worth at least tapping the brakes so that the lights go on and warn someone else behind you that you are slowing, particularly if you are downshifting such that you're going to slow quickly. You don't really even have to use the brakes, just tapping them is typically enough.
This is a big deal on motorcycles, which—due to the size of the engine relative to the weight of the vehicle—can engine-brake very hard. (Hard enough that some have a 'slipper clutch' which is sort of like a bicycle freewheel in order to cut down on undesirable engine braking!) I have often thought of installing one of those MEMS accelerometers on my bike to trigger the brake lights under engine braking, since it is an easy way to end up dead.
Having someone 'tap' you from behind isn't as disastrous in a car as it is on a motorcycle, but it's still a good way to ruin an otherwise-fine morning.
posted by Kadin2048 at 4:19 PM on October 28, 2014 [2 favorites]
I think we've stumbled into some sort of religious war here that I don't really want to perpetuate, but I think it's worth pointing out that if you ONLY engine-brake, without using the brake pedal at all, you will not trigger your car's brake lights. It may dramatically increase the risk of someone running into you from behind.
So it is worth at least tapping the brakes so that the lights go on and warn someone else behind you that you are slowing, particularly if you are downshifting such that you're going to slow quickly. You don't really even have to use the brakes, just tapping them is typically enough.
This is a big deal on motorcycles, which—due to the size of the engine relative to the weight of the vehicle—can engine-brake very hard. (Hard enough that some have a 'slipper clutch' which is sort of like a bicycle freewheel in order to cut down on undesirable engine braking!) I have often thought of installing one of those MEMS accelerometers on my bike to trigger the brake lights under engine braking, since it is an easy way to end up dead.
Having someone 'tap' you from behind isn't as disastrous in a car as it is on a motorcycle, but it's still a good way to ruin an otherwise-fine morning.
posted by Kadin2048 at 4:19 PM on October 28, 2014 [2 favorites]
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So you're both right, in theory it's possible that his method could save you some brake pad wear.
In practice, though, everyone driving the automatic version of your car is just braking, and it's a hell of a lot more expensive to replace the clutch or do transmission work than it is to swap out brake pads.
I used to be a "shift for everything" sort of person, now I'm of the "unless it's a big long downhill and you're maintaining speed, just use the damned brakes" camp.
posted by straw at 4:57 PM on October 23, 2014 [14 favorites]