Am I destroying my clutch?
June 20, 2008 9:03 AM   Subscribe

Is it bad to keep my clutch pedal pushed all the way in as I brake for stop signs and turns? Should I instead shift to neutral, let the pedal out, and then shift back into gear when I need it?

I seem to remember this being discussed on Car Talk a while back, and their objection was something about not having full control of the car when you do this, but that doesn't really make sense to me. I think they were talking more about engine braking vs. pedal braking on hills and such.
posted by Who_Am_I to Travel & Transportation (33 answers total) 8 users marked this as a favorite
 
I believe that it wears the clutch out, and as such is bad from a mechanical point of view. As for less control, probably slightly true - it will take you longer to accelerate, with the possibility of stalling when you do so (e.g. there's a need to take evasive action, so you need to accelerate).
posted by djgh at 9:13 AM on June 20, 2008


You shouldn't "ride the clutch" - that is the clutch pedal should be all the way up, or all the way down - anywhere in between can cause wear and shorten the life of the clutch. So holding the pedal in at a stop light, in preparation for shifting is perfectly fine.

As for downshifting - this too causes wear and unless you need fast acceleration it's also not a good idea. Brake pads are a helluva lot cheaper than a clutch or transmission.

UNLESS - you're experiencing brake fade - particular when traveling downhill. This should be a problem on modern vehicles, but is an issue for large trucks. In this case down shifting may make sense from a safety point.
posted by wfrgms at 9:14 AM on June 20, 2008 [1 favorite]




Stop lights: shift to neutral, foot off clutch

Stop sign: clutch in, downshift to first, keep the clutch in until stopped, then accelerate

By the way, Coasting in gear until any kind of stop saves gas, whereas coasting in neutral uses gas and is unsafe.
posted by limited slip at 9:15 AM on June 20, 2008


Holding the clutch in puts a little bit of wear on the throw-out bearing. In general, though, the bearing will still outlast the clutch plates.

I keep the clutch in for short stops and let it out when I expect a longer stop, but it is purely for comfort, not for the life of the clutch.
posted by indyz at 9:16 AM on June 20, 2008


Coasting in gear until any kind of stop saves gas, whereas coasting in neutral uses gas

?
posted by tachikaze at 9:18 AM on June 20, 2008 [1 favorite]


Well, mechanically speaking, the neutral position is "nicest" to the car. When you have the clutch depressed, a lot of people say you're putting wear and tear on the clutch's throw-out bearing, which may necessitate a clutch job sooner than normal. However, I'm not familiar with any first hand stories of the throw-out bearing actually wearing out as a result of this.

From a control point of view, you want to be in gear all the time, never in neutral. This gives you the ability to react to sudden events with all three of your potential inputs -- steering, braking, and accelerating. In fact, in my state (RI), it's technically illegal to coast in neutral, and I suspect the reason is safety. (Doesn't mean I don't still do it sometimes.)

Personally, I don't usually get into neutral unless I'm at a traffic light that's going to last more than a few seconds. If it's going to last more than 10 seconds or so, I sit in gear with the engine off, clutch out (as if I'm parked), and restart the engine and go when the light's green.
posted by knave at 9:20 AM on June 20, 2008


By the way, Coasting in gear until any kind of stop saves gas, whereas coasting in neutral uses gas and is unsafe.

If by "coasting" you mean "engine braking", yes. When you're decelerating in gear, a typical fuel injected car is injecting zero fuel. If you depress the clutch or shift to neutral, the car will burn a small amount of fuel to idle the engine.
posted by knave at 9:21 AM on June 20, 2008


Coasting in gear until any kind of stop saves gas, whereas coasting in neutral uses gas

As long as your engine is above idle speed, when you coast (or more accurately engine brake) in gear, the momentum of your car keeps the engine turning, so no fuel is injected. When you coast in neutral, your engine idles and uses some small quantity of fuel to keep itself going (in my car, about 1ml for 10 seconds).
posted by ssg at 9:24 AM on June 20, 2008


You remember correctly. You're heating up and using up your brakes. Additionally, by shifting into neutral or keeping the clutch down, you indeed won't be able to accelerate if you see the car behind you isn't stopping, and you'll travel much further if you're rear-ended.

Imagine you want to slow down for a stop sign. With your right foot barely touching the brake lever to make the braking light go on, downshift to second gear like you usually would, fully release the clutch, and let the engine do the braking. Only once you have slowed down enough and you can hear the engine struggling should you engage the clutch and brake.

Recap:
  1. Caress the brake pedal with your right foot
  2. Downshift to fourth, to third, to second, easing on the clutch between gears to spin the wheels down
  3. Release clutch
  4. When you're getting close to stalling, engage clutch
  5. Brake
Practice on an empty road, because you will either stall or disengage the clutch too early at the beginning. You want to be able to only have to give the brake pedal a short nudge, gently release it and let the car roll to a complete, gentle halt.

At least that's how they teach it in Europe.
posted by stereo at 9:24 AM on June 20, 2008


stereo, in my opinion you're missing in step 2 "blip the throttle to match the engine RPM to where it would normally be in that gear, at that speed". In other words, don't make the clutch do the work of dragging the engine up to speed, which is a lot of friction (wear). Rev match the engine speed to the clutch disc and, when done perfectly, you don't even feel the clutch engage.
posted by knave at 9:38 AM on June 20, 2008


thanks for the elaboration knave.
posted by limited slip at 9:38 AM on June 20, 2008


I'm still having trouble seeing how coasting, i.e. toolin' along not trying to decrease speed, in neutral uses more gas than being in gear, engine braking. The work of compressing the intake gasses equals a deduct in speed, whereas coasting - in neutral- only has decreases due to drag and elevation.
posted by notsnot at 9:56 AM on June 20, 2008


I'm still having trouble seeing how coasting, i.e. toolin' along not trying to decrease speed, in neutral uses more gas than being in gear, engine braking. The work of compressing the intake gasses equals a deduct in speed, whereas coasting - in neutral- only has decreases due to drag and elevation.

While coasting in gear, the movement of the car keeps the engine spinning, no need to inject fuel to keep it from stalling. When the car is in neutral, the engine is not kept spinning by anything except momentum, which runs out quickly. If the engine stops spinning, you stall, so it injects fuel to keep it from stopping.
posted by InsanePenguin at 9:59 AM on June 20, 2008


No one has asked what you are driving.

Jesus...

Some clutches/gearboxes are better than others. If you have a VW, don't mechanical brake.

If you have a Porsche, go nuts.
posted by Zambrano at 10:01 AM on June 20, 2008 [1 favorite]


wfrgms hit it right on the head.
posted by peewinkle at 10:06 AM on June 20, 2008


If you push the clutch in, your engine revs drop to idle. This means that your power accessories, most importantly steering and brakes, can lose power assist. It actually takes a lot of braking or steering in this situation in order to deplete the pressure in the lines. The only situation where you'd probably be doing that much is an unanticipated need to evade a collision, but that's exactly the point: do you need to add "blip the throttle and put the car back in gear" to your list of urgent tasks at the moment you're trying to avoid an accident?
posted by ikkyu2 at 10:09 AM on June 20, 2008


notsnot: The assumption here is that you have enough momentum to make it to the stop line with engine braking (i.e. coasting in gear).
posted by ssg at 10:10 AM on June 20, 2008


Thanks everyone so far. To clarify, what I normally do when approaching a turn is put the clutch in and move the shifter to 2nd or whatever, brake as necessary, and then engage the clutch to accelerate through the turn. For any sort of full stop like a red light I'll do the same thing when slowing, but shift to neutral and let the clutch out once I've stopped.

I was taught to use just the brakes for braking (cheap to replace, avoid engine wear etc.), but limited slip makes an interesting point about fuel use. stereo, that seems like a lot of clutch use just to make the engine to the brake's job. Of course, I could have been taught wrong ;)

BTW, this is a bare bones '98 Hyundai Accent, so no power anything.
posted by Who_Am_I at 10:20 AM on June 20, 2008


When the car is in neutral, the engine is not kept spinning by anything except momentum

which is why engines have flywheels.

According to ssg's number above, with $5 gas it costs one-hundredth of a cent of gas per second to idle the engine.

Assuming one idles for 5 minutes per week, that's . . . $1.50 per year in gas cost for not habitually grinding your clutch down.

I've got 80K+ miles & 8 years on my original clutch. I sometimes downshift at stops for fun, but don't do it to save money, cuz that's stupid.
posted by tachikaze at 10:22 AM on June 20, 2008


RRRRGGGGHHHH!!!!! I hear people say this all the time, but IF YOU"RE COASTING NOT COMING TO A STOP, i.e. I'm on the big hill coming down Hampton ave, no one around, no stop lights I need to stop for, if I put it in neutral, I'm using a modicum of gas. I get to the bottom of the hill, still doing 40, and I can put it in gear and keep scootin'. If I leave it in gear, I'm not using any gas, sure, but the energy required to compress my intake air scrubs momentum from my vehicle, and I'm doin' 20 halfway down the hill. I then have to blip the throttle and keep it at 5% open to get back up to 40. How in the HELL can anyone with half a lick of mechanical knowledge say that this is saving gas vs coasting in neutral?
posted by notsnot at 10:23 AM on June 20, 2008 [1 favorite]


notsnot: That's all fine and dandy, but there is no need to be upset. The original question was specifically about coming up to stop signs and turns and limited slip's comment was specifically about coasting in gear up to a stop. No one here is making any kind of argument about coasting down long hills.
posted by ssg at 10:46 AM on June 20, 2008


Who_Am_I: the technique you're using now sounds like the perfect compromise between the "keep it in gear and downshift all the way" people and the "put it in neutral" people. I say keep doing what you're doing. You may be putting a little bit more wear on the throwout bearing, but it's negligible.
posted by zsazsa at 10:52 AM on June 20, 2008


Very much depends on the car, it knows it's master. Loan your car to someone else, who may know how to drive better than you, and repairs are in order.
posted by StickyCarpet at 11:30 AM on June 20, 2008


I've got 80K+ miles & 8 years on my original clutch. I sometimes downshift at stops for fun, but don't do it to save money, cuz that's stupid.

I understand what you mean, and I guess it doesn't really make sense with adding the extra wear and tear on the clutch. Technically, however, it does use less gas. You win in any case, common sense comes out on top yet again!
posted by InsanePenguin at 12:38 PM on June 20, 2008


Engine braking in cars is a holdover from ol' timey days when brakes were less 'reliable', or so I heard somewhere.....
posted by toastchee at 12:57 PM on June 20, 2008


I've been braking by putting the car in neutral for years; I always assumed it was better on the car than engine braking, and I had heard the same thing as toastchee. I guess I'll change now - thanks guys!
posted by btkuhn at 6:52 PM on June 20, 2008


which is why engines have flywheels.

Er. No. Flywheels are to smooth out the pulses from the firing order. Not to keep the engine running.

your engine revs drop to idle. This means that your power accessories, most importantly steering and brakes, can lose power assist

This is not, in any slightest way, true. None of these will be affected by an idling engine.

Yes, holding the clutch in will accelerate clutch release bearing wear. Yes this can very much happen before plate wear. Frequently.

Keeping the drive engaged is a better method as it does allow fuller and more consistent control of the car.

Engine braking in cars is a holdover from ol' timey days when brakes were less 'reliable', or so I heard somewhere.....

This is not at all true. It was just more important when brakes were crap. It is still a very effective and efficient way to slow the car, and has almost zero wear on any components to do so. Brakes are a friction device and will always wear upon usage.

There is nothing wrong with downshifting, but if you are decellerating gently, there's no need to do so unless you fall below a sensible road speed for the car. A lower gear will decellerate you more quickly, which is good. The extra wear is marginal.
posted by Brockles at 7:47 PM on June 20, 2008


Note that in most states, coasting in neutral is illegal, because it increases your effective reaction time, should you need to accelerate out of the way of an accident in progress. IIRC the WA drivers manual says sitting at a stop light in neutral or park, was a no-no too, but on the other hand, I see signs all up and down our drawbridge approaches telling people to turn off the car while waiting.
posted by nomisxid at 8:35 AM on June 21, 2008


Where do you think the power for power-assisted brakes and steering comes from, Brockles? Hint: it's the engine. Most engines don't supply enough power at idle to maintain power assist for very long. Learn about it.
posted by ikkyu2 at 9:02 AM on June 21, 2008


Where do you think the power for power-assisted brakes and steering comes from, Brockles?

Power steering comes from a belt drive off the engine. There is more than enough power in an idling engine to run the pump. How do you think you manage to park? Steering at speed uses much less assistance than parking, and have you ever had a car stall when parking? (Assuming a properly functioning one). Load on the power steering pump will create extra load on the engine, which will be compensated for almost instantly by the ECU to increase fuel to match the higher load.

Brake assistance comes from using the vacuum generated by the engine in the inlet manifold. Again, the engine will generate far more than the assistance you will require while still at idle. Repeated applications of the brake may cause less vacuum to be there to assist, but unless you are sat at idle, stationary, repeatedly stabbing the brake on and off you won't perceive an issue - you may hear the engine revs drop a little (until the idle controller compensates) but you won't have a braking issue. A few applications of braking at speed will not see any significant/noticeable/problematic issues with the vacuum available for braking performance.

Most engines don't supply enough power at idle to maintain power assist for very long.

That is simply not true. The load requirements are tiny by comparison, and the engine will automatically change the fuelling to accommodate the different conditions. All engines are capable of providing that load and more (including charging the battery and running the aircon, in most cases) indefinitely - or until the fuel runs out. And I don't think you'll be coasting that long, do you?

There will be absolutely no issues of the type you describe. There is in no way any time limit on how long your car can sustain assistance for. It is nonsense.
posted by Brockles at 3:18 PM on June 21, 2008 [1 favorite]


I'm late to the game. But yeah I just bought a standard recently and trying to figure out exactly this issue. Everything I've read sounds just like this forum. No consensus! Engine braking = increased wear or no it doesn't. Coasting with clutch in = increased wear or no it doesn't. And finally, engine braking saves gas... or... no it doesn't (well it does to the tune of 1.50$ a year but at the expense of your engine).

I've reverted to driving my car like I did my dirtbike growing up. Clutch in when I damn well feel like it (for coasting, for turns, at stop signs, etc.).
posted by Smegoid at 6:54 PM on June 21, 2008


Everything I've read sounds just like this forum. No consensus!

Not really. There is a consensus among those that actually know, and an awful lot of guff from people that repeat urban myth, personal anecdotes based on two instances in the past and things their grandfather mentioned once at Christmas.

The sheer level of noise from people with only partial knowledge makes it very hard for people to spot the consensus, though.
posted by Brockles at 7:27 PM on June 21, 2008


What Brockles said.
posted by knave at 8:01 PM on June 21, 2008


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