car trouble deja vu

November 28, 2006 10:25 AM

My car has developed pulsing brakes and a low-speed wobble, for the second time in under 2 years. Help me get it fixed right this time, please?

My car wobbles from side to side slightly at low speeds. The wobble frequency varies with the speed of the car, becoming a mostly non-noticeable vibration above ~20 mph. Also, the brakes apply in a jerky/pulsing manner that again varies with the speed of the car and isn't noticeable until I'm going quite slowly. It feels to riders as though I'm pumping the brake pedal, even though I'm applying constant pressure. It feels to me like the brakes don't catch as well during some parts of the wheel's rotation.

My question partially involves these symptoms, but mostly involves the fact that this has happened before. These same two problems occurred together about a year and a half ago. It all began a few months after I had 4 new tires put on the car. (Bear with me - I know very little about cars, so I'm about to pull terms from memory that I didn't fully understand when I heard them.)

I was told at the repair shop that my brake rotors were bent and needed to be re-machined (to fix the jerky brakes), and also that one of my tires was probably out of round (to explain the wobble). The mechanic fixed the brake issue, but said the tire guys would have to deal with the tire issue. However, he did rotate the tires so that the wobble would be in the back of the car instead of the front until I could make it to the tire store - this made driving the car somewhat easier/less nauseating. He also said to tell the tire guys to be sure to use a torque wrench next time they did the tires. He seemed to be implying that the lack of a torque wrench might have caused the bent brake rotors.

A few days later I went to the tire store and told them about the wobbly tire and that the mechanic thought it seemed to be "out of round". The tire guys took a look, did some stuff, and told me that one of the tires just needed balancing. I didn't mention anything about the torque wrench, because I'm kind of shy and didn't feel qualified to be telling the tire guys how to do their jobs.

So, approximately a year and a half later the problem is back. This time I want to know what I'm talking about when I go to get it fixed, so maybe it will STAY fixed. I'm done being shy. Here are my questions:

1) Does the original diagnosis sound correct - bent brake rotors and a bad tire? I mostly assume the mechanic was right, because the problems went away (for 18 months, anyway) after he fixed the brakes and the other guys messed with the tires.

2) Should the tire people replace my tire(s), or is re-balancing it/them ok? As I understand it, re-balancing just shaves rubber off of part of the tire, which won't solve the problem if the tire is truly "out of round". How do I know whether the tire really has an irreparable flaw? Should I demand a replacement? This is at a national discount chain, and at this point I don't really trust them to thoroughly handle the matter unless I ask the right questions and really push.

3) Could the tire guys' installation techniques, or the bad tire, have caused my brake problems? If so, should the tire store have to pay for fixing my brakes, especially if they should have replaced the tire the first time this happened instead of just rebalancing it? Should I mention the torque wrench thing this time?

4) Could there be something else wrong with my car that is causing both of these problems to come up again? I've been blaming the tire and possibly the tire people for not fixing it right the first time, but if something else could be making this happen then it'd be good to know.

Other details that may or may not matter:
The car is a '96 Civic with only 60,000 miles on it, automatic transmission. I bought it from my grandparents just over 3 years ago. It was in a major accident that required significant rebuilding at some point well before I purchased it, but my grandparents didn't experience any problems with it after the rebuilding.

posted by vytae to travel & transportation (17 answers total)

Original diagnosis is not obviously wrong, but there could be other things. The mechanic hit on the most straightforward stuff though.

Rebalancing does not involve "shaving the tire". They balance the tire by putting small metal weights on the rim of the wheel (the metal part in the middle that the tire is mounted on; yeah, kind of obvious, but not everyone is clear on the difference between tire which is the rubber part and wheel which is the metal part). If the tire itself is "out of round" then it needs to be replaced. If you have a warranty on the tires, this may be covered totally or partially, based on the number of miles on the tires.

Warped rotors can be caused by hard braking. If you have a lead foot on your brake, you may be causing the rotors to warp by your driving style. Basically, the rotors warp when they are heated up suddenly and are not allowed to cool evenly (as in the part that is next to the brake pad stays hot longer). Two solutions in terms of driving style is to try to go easier on the brakes, or stopping, then rolling forward a little more (like a couple feet) after coming to a full stop.

There are other things that can cause wobbles and vibrations, but brake rotors, and wheels and tires are usually what does it.

Your brake rotors may have been perfectly fixed last time, but they may have rewarped.

One last thing: You said this happened 18 months ago. Have you rotated your tires (i.e., move the ones on the front to the rear and vice versa) during that time? Leaving tires in the same position on the car for a long time can cause uneven wear which leads to vibration. Rotating your tires every 6 months or 6000 miles, and making sure you have the right air pressure, are the best way to ensure long tire life.
posted by Doohickie at 10:41 AM on November 28, 2006

Underneath the obvious answers - there's no argument with Doohickie's diagnosis - is one that can be kind of difficult to diagnose: a failing wheel bearing. If the bearing is failing but not yet noisy you can get enough slop in the wheel to a) knock back the brake pads (do you find that after rounding a curve, the brake pedal goes further to the floor on its next application? That's diagnostic) and b) give the other symptoms you mention.
posted by jet_silver at 10:48 AM on November 28, 2006

All tires are out of round. If you don't believe it, put a dial indicator on one you're sure is round. If they are so far out of round that they cause noticeable wobbling, they're defective and should be replaced. If the wheel is bent, it should be replaced.

The part of Doohickie's rotor-warping technique that was left out is that the hard braking should be followed by parking the car. If the car keeps moving, the caliper won't rest on one spot, and the rotor should cool evenly. Do you work right next to the freeway, so that you slow down a from highway speeds, pull right into the lot, and park? A friend of mine had rotors that warped repeatedly from just that. Try getting off the freeway one exit earlier, and drive slower streets from there.

I think it's unlikely that mis-torqued lug nuts would warp a brake rotor, unless the wheel was not fully on, or some of the nuts weren't tight.
posted by Kirth Gerson at 10:56 AM on November 28, 2006

Mid-90's Hondas, especially Accords but also civics, were know for warping rotors just by looking at them - and by improper torqueing of the lugnuts.
posted by notsnot at 11:24 AM on November 28, 2006

In addition to all the other very good suggestions, I've had this same symptom with a broken belt in a tire. Look for a bulge in the sidewall. Simply replacing the tire with a good one fixed it.
posted by Floydd at 11:27 AM on November 28, 2006

In addition to the above, it sounds to me like a wheel weight fell off. I have had the same happen.
posted by wzcx at 11:56 AM on November 28, 2006

Warped rotors, when replaced, must also have the pads replaced if they are glazed. Glazed rotors will always make for warped rotors.
posted by kc0dxh at 11:56 AM on November 28, 2006

Warped rotors can be caused by hard braking.

Misleading, they're almost never actually warped, just worn in a ripple pattern. A 'turning' or machining will repair this if there is enough material left on them. This is usually caused by hard braking and a complete stop just after new rotors are installed (or when the car is new). This leaves uneven brake pad material deposits on the surface which cause uneven wear. In extreme cases you can see an imprint of a brake pad on the surface. (BTW, they gray sheen you seen on rotors and what keeps them from rusting so quickly is this very deposit. There is a procedure to break these things in properly, do a search. Drive to 60, slow down hard to 10 and release brake, accelerate, repeat 8 or 10 times.)

Tires and that weaving, bobbing and dodging sensation:

(I'll just agree with the broken belt and/or blister)
posted by IronLizard at 11:57 AM on November 28, 2006

He also said to tell the tire guys to be sure to use a torque wrench next time they did the tires. He seemed to be implying that the lack of a torque wrench might have caused the bent brake rotors.

He was complaining because they probably used an impact(air) wrench and he had a hell of a time getting them loose and/or they screwed up the nuts and/or threads. On the other hand, they may have been loose. A torque wrench just ensures that they're the exact tightness the manufacturer recommends. Nothing to do with your other problems.
posted by IronLizard at 12:01 PM on November 28, 2006

Thanks for all the input, everyone.

Doohickie: I didn't realize that tires were supposed to be rotated that often, so no, I haven't been doing it. I'll definitely keep up with it now that I know. Thanks for all the other great info, too.

jet_silver: The pedal doesn't push down any differently after turns, so I don't think it's the wheel bearing.

Kirth Gerson: I can't think of anywhere that I regularly go where I stop very soon after getting off the freeway. My work commute is only a couple miles over city streets.

kc0dxh: I don't think I have the car vocabulary to understand your comment, but now I'm concerned. How can I tell if I have glazed rotors?

I don't tend to hammer on the brakes, but it has just now occurred to me that I have a habit of bouncing my foot on the brake pedal while sitting at a stoplight (to accompany the steering-wheel drumming, naturally) - not enough to allow the car to move at all, just enough that my heel taps the floor while my toe keeps the brakes engaged. It sounds like my car might be fragile enough that this is a bad idea, so I'll stop.

Everything I'm finding on google about breaking in new breaks is aimed at the racing community. Can anybody give me some more info or links on what I should be doing? Do I need to do it if the mechanic machines the rotors? What if they replace the break pads?
posted by vytae at 12:57 PM on November 28, 2006

If the car remains stopped while you're doing it, toe-tapping has zero impact on the brakes. Brakes are only worn or heated up when they are applied while the wheels are turning. Once you stop, no more wear or heat is generated. Party on.
posted by Kirth Gerson at 1:22 PM on November 28, 2006

Much of what Doohickie advised is correct. I'll expand a couple of points.

The type of stop he's describing is called a chauffer's stop. It is accomplished by applying hard brake pedal force at the beginning of braking, when the relative wheel motion to vehicle is greatest, and most braking effect can be created on dry pavement, with a subsequent gradual lessening of pedal force until just before the moment when the vehicle stops, at which instant, the brake pedal is released completely. The driver is trading on the difference between sliding friction, which is the usual kind of friction available in the brakes of a car in motion, and static friction, which is what holds a car in place on a grade when the brakes are applied. (You may have heard these terms in a basic physics course describing types of friction and Newtonian forces.) The transition between sliding and static friction is what you are trying to avoid in the last instant of stopping. The advantages are that 1) you avoid the coffee spilling small "jerk" that will inevitably happen if you keep brake pressure through to full stop, and 2) you minimize the considerable brake wear that occurs when particles of your pads are yanked by the sudden occurrence of static friction at the end of every stop you are now doing.

I routinely get 75,000 to 100,000 miles between brake jobs on American sedans and light pickup trucks doing chauffer stops. If you aren't getting at least 60,000 miles between brake jobs on a car as light as a Honda Civic, you are either living in Puerto Rico, or some other place where hellacious brake and tire wear come with the territory, or you're doing something very wrong in braking. Once you've got your brakes repaired, go to an empty parking lot on a Sunday morning, and practice accelerating and stopping from 20mph, releasing the brake pedal at the instant before you think the car is completely stopped, until you can come to a full stop, without jerking, reliably, every time. Most people get this down in about 20 minutes, once they know what they are trying to achieve.

Next, over torquing or unevenly torquing cast disc rotors surely will warp them, because the pressure of the lug bolts which are pressed into the disc rotor, against the wheel varies from the designed pressure when the torquing force is out of spec. The lug studs do not stretch the amount intended by their designer in establishing the torque spec, and the forces sent through rotor to the rest of the vehicle are enough to damage it, in a few thousand miles of normal driving. Warped rotors can sometimes be "trued" by machine work, but rotors with such significant issues as you describe have probably been worn beyond machining tolerances, and will have to be replaced.

An air operated "impact wrench" is used at many tire shops to remove and retighten wheel lug nuts. If the tool is treated well (oiled regularly, not dropped on concrete, used with a good air supply, etc.) it can produce reliable and repeatable torque readings. If you go to a shop where guys are treating expensive air tools badly, or you see water mist shooting out of air guns and other equipment, you need to be doing business elsewhere.

Various grades of replacement rotors and pads are available in the after market, at various price points. Some of the OEM (original equipment manufacturers) specification parts may be adequate for most driving, but it sounds as if you are pretty hard on your brakes. You may want to investigate some of the "performance" brake kit parts available for Civics, as these rotors and pad combinations can withstand higher heat with less fading, and less risk of damage. Complete "performance" brake kits are available which replace the stock rotors, calipers, and pads with better components, and many people replace even such things as the brake system hydraulic lines, brake fluid, and master cylinder and brake vacuum booster, for even more improved pedal feel, and greater fade resistance. You can spend hundreds and hundreds of dollars on the top of the line "street racer" kits, but you, at least, should look into better than OEM grade rotors and pads, if you'll have to be replacing them any way.

In so far as your question regarding "break in" of new brakes is concerned, there is no special technique required for modern brake systems, other than to avoid long applications of the brakes from high speeds in the first few thousand miles. Keeping your speed controlled with the accelerator and transmission, and not the brake pedal, is what you are aiming for. If you drive an automatic transmission car, you don't want to have a habit of "riding" your brakes, "getting ready" to stop. Either apply brakes forcefully, or get your foot on the accelerator lightly. Don't ever "rest" your foot on the brake pedal. This is generally second nature to stick transmission drivers, but automatic drivers often "ride" their brakes, trying to keep their tranmission from creeping their vehicle forward. Shift into neutral if you must idle, and give your brakes, and your foot, a rest.

There is really no reason a new set of brakes on a Honda Civic shouldn't last a 100,000 miles of normal driving, if treated with just a little care.
posted by paulsc at 2:00 PM on November 28, 2006 [1 favorite]

Warped rotors can sometimes be "trued" by machine work, but rotors with such significant issues as you describe have probably been worn beyond machining tolerances, and will have to be replaced.

Paul, I applaud your excellent comment. That was beautiful. But I do have to point out that rotors almost never warp.
If they were, in fact, warped, they would be unserviceable even after machine work. The reason for this is apparent if you look at a cross section of the rotor and imagine a twist in it. Even if the deformation is slight the machine work, which only operates by removing material from the faces, would leave thin and thick spots and render it very vulnerable repeating the same problem shortly and to breakage at high temperatures/loads. Not to mention making the thickness measurements somewhat inaccurate.

As to the break in procedure, if you drive the way paul does: you don't need to worry about it because his particular style of driving is doing essentially the same thing, though probably over a longer period of time.

I've used cheap pads for years, always had this problem till I started breaking them in. My driving is very ummm, erratic.

Also: What tire shops do you go to? Impact wrench != torque wrench. Not by a long shot.

Now that's not to say that there are no pneumatic torque wrenches available (there are!). It's just that most tire shops, especially the little shack types and many sleazy brand names ones, don't bother shelling out the cash for something like that.
posted by IronLizard at 3:59 PM on November 28, 2006

I didn't realize that tires were supposed to be rotated that often, so no, I haven't been doing it. I'll definitely keep up with it now that I know. Thanks for all the other great info, too.

I found that out through experience. My wife put 60,000 mile tires on her car, and after 25,000 miles they were so unevenly worn they had to be replaced. By not rotating them, if there is something that is creating uneven wear, it just gets worse and worse. By rotating them, it takes that tire out of that "bad environment" and moves it to a different one, and the imperfections in the different positions on the car can (if the wheels are properly aligned) essentially cancel each other out.

Luckily for us, I noticed this on a long trip. We bought the tires at a Pep Boys in Texas and took the car to a Pep Boys in Buffalo, NY. They kind of felt sorry for us and honored the warranty even though it was pretty obvious the tires hadn't been rotated.

Many tire outlets will rotate and balance your tires for free as part of the purchase price of a set of tires. So depending on where you bought them, maybe you can just take them back and they will take care of it for you.

The two methods that have worked for me in cases like this are the "sympathy ploy" (like with Pep Boys.... we were so far from home and needed good tires so my family would be safe), or, the "stubborn, just shy of exploding, almost losing your temper, I'm not leaving until it's fixed" ploy. The second one is harder to pull off, especially if you're not sure what you're talking about. Try the sympathy ploy, but don't let them walk all over you.

Good luck.
posted by Doohickie at 9:30 PM on November 28, 2006

Paulsc, wow, thanks for all the info. Does "Shift into neutral if you must idle, and give your brakes, and your foot, a rest" mean that I shouldn't have my foot sitting on the brake while I wait at stoplights? I paid attention on my way home last night, and everyone's brake lights were on while sitting at stoplights - are we all supposed to be shifting into park while we sit there instead?

As for the chauffeur's stop, I totally thought I invented that technique as a teenager to convince my mom that I was a really great driver (worthy of taking the car out on my own). It's interesting to find that it has a name. I guess I'll try using it all the time, instead of just when I have nervous passengers.

I had my tires done at Discount Tires (based on several great recommendations from friends). They do free rotations and I'm pretty sure I bought the extended warranty/free replacement deal at the time too, so I'll go back and have them rotate and check everything out. I've been neglecting the issue because I've moved apartments and jobs since I got the tires originally, meaning their store is much more out of the way for me. I guess it's time to make the effort.
posted by vytae at 7:25 AM on November 29, 2006

Even if you shift to Neutral when stopped, do keep your foot on the brake. If someone bumps you from behind at a red light, and your foot's off the brake, you could find yourself suddenly entering cross traffic. The extra half-second it would take you to get back on the brake could make a big difference.
posted by Kirth Gerson at 9:08 AM on November 29, 2006

I've been neglecting the issue because I've moved apartments and jobs since I got the tires originally, meaning their store is much more out of the way for me.

That right there is the sob story to use for your sympathy ploy if they give you a hard time. I would go in, request a rotate and balance and just ask them to check everything out since you feel a bit of a wobble. When they balance the tires, if there is anything more than a rebalance necessary, see if they will easily help you out.

If not, then mention that you really had good intentions, but with moving and everything you haven't had a chance to come back before now and this is your first car and you're trying to learn, etc., etc. Keep it sounding positive and make sure they know how much you appreciate their help.

I haven't actually used Discount, but they have one of the best names in the business and I am considering going to them for my next set of tires.
posted by Doohickie at 9:55 AM on November 29, 2006