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Shimmy when braking

36K views 29 replies 11 participants last post by  E_Net_Rider 
#1 ·
IHA 97 malibu 2.4L. I did the brakes earlier this year. No brainer there. However, over the last few months when braking the front shimmy's. It vibrates badly when braking at high speeds. At slow speeds when I brake it feels like they are grabbing and relaesing slightly. Are the rotors bad? I had the tires rotated recently and they said the brakes were good, however the place I took my car for the tire rotating is subject to less than honest opinons.

Ideas? Thanks!

Happy Holidays!
 
#2 ·
Yes, your rotors are warped. If the vibration is heaviest when you first hit the pedal at highway speeds and then goes away as you slow or increase pedal pressure, that would indicate the rears, if the vibration gets worse as you slow, then it would indicate the front. Usually that happens from techs not using a torque wrench when changing the tires. You may be able to have the rotors turned, but the price of rotors has really come down the last couple years so it might be better to just buy new thick rotors rather then to turn them and have thin used rotors. If you buy new and replace yourself be sure to use a torqe wrench when putting the tires on and clean the new rotors as they have a protective film on them to keep from rusting in the box. If you don't clean them with a parts and brake cleaner they could glaze over and not work so good.
 
#3 ·
The vibration is heavy when braking at freeway speed but then lessens as I slow. If I really stomp on the brakes the vibration is less. The rear brakes are drum. The front, obviously, are disk. So am I looking at replacing the drums in the rear or the rotors up front? I heard the 97 Malibu needs a press to put the rotors back on. Is that correct?

Thanks for your help!
 
#6 · (Edited)
Front or rear? That is the question. Let me see if I can give a better recap of what is happening; when at freeway speeds, when the brake is applied, the steering wheel vibrates badly then subsided some as I slow or if the brakes are applied hard at a quick stop. When traveling at slower speeds, it feels like the brakes are grabbing and then releasing briefly as I come to a stop. Either way the steering wheel feels like it is puliing to the left and right while that is happening. There is a rubbing round coming from what sounds like the front as I stop. Not a grating sound becasue the front pads and rear shoes are realativly new.
 
#7 ·
Get a pair of new front rotors. Relatively inexpensive and easy to swap. As others said, USE a torque wrench to get the lug nuts on evenly. Make sure to clean and relube the caliper mounts/slides for even operation. It's relatively rare for drums to get warped on these lightweight cars...

Locally new rotors are about the same price as having old ones turned, if there is even enough metal left to do a proper job. Labor is the same so why not have new brakes?
 
#10 ·
caused by cheap material in the rotor. GM will tell you its caused by people not using a torque wrench on the wheels, they dont ever want to admit there own mistakes.

no offense to anyone, but a torque stick will get the torque where it needs to be. its limited to a set spec, yeah it wont be exact like a torque wrench, but it will be close.
i can see if its like 90 ft lbs on one nut then 130 ft lbs on another, but thats pretty inconsistant. im sorry but i just dont believe in the whole "oh its caused by people using torque sticks" gig. hey if you want to use a torque wrench on everything, go for it, i like to eat during the week and not take 15 minutes to a tighten wheel on every car that comes in the door.
 
#12 ·
Being ASE certified then you must know that the ASE no longer recognizes torque sticks as an accepted alternative to a torque wrench. There are two reasons for that. One is metal fatique from the constant flexing. The other has to do with the wide variety of impact wrenches and the degrees of turn in each stroke. If you had one that was limited to say 1 degree, then you could expect quite uniform tightness, but if you have one that is like 15 degrees, there is likely a wide range of torque. Not exactly on the numbers, but you should get the idea.
 
#11 ·
Uh the proper thing to do is torque the wheels to specs, they recommend it for a reason. an improperly torqued fastener can either strech it beyond it's holding ability or if it's not enough cause it to loosen up. Torque sticks suck and are not even close to being acurate. I'd put a torque wrench to any wheel I've taken off and put back on, I surely wouldn't want a wheel to come flying off a car and be liable for the damages.
 
#15 ·
Is that only when you step on the brakes ??
If not, it probably is an entirely DIFFERENT problem.

It could be the rears too.......or only one rotor.

It would be better to first find out where the problem really IS before changing out parts.

If it is the rotors, they often can be "turned" cheaper than replacement.
 
#16 ·
First thing, there is no such thing as warped rotors. Pulsing/shimmy can be caused by a lot of things. Uneven brake pad deposits on the rotor, rust spots on the rotor (check the back side of the rotor), lateral thickness variation, excessive wheel bearing run out or excessive run out on new or used rotors. Throwing parts at a problem is a good way to spend ten times what it would cost to inspect and analyze the brakes to find out what is causing the shimmy. Uneven brake pad deposits may be taken care of by going out and doing about 20 hard stops from 25 mph to 5 mph without locking up the wheels.

Bill
 
#17 ·
It's ignorant to say rotors never or can't warp. I see it all the time. I would call lateral thickness variation warping. And the cure is to replace or turn the rotors.
Excess wheel bearing run out will cause a low brake pedal, not a shimmy, and I've never seen any kind of pad deposits on a rotor. Just saying...
 
#18 ·
Sounds like someone is a paid mechanic....lol I replaced the rotors yesterday, no more shimmy. I purchased the high end rotors and they where obviously higher quality than GM put on stock. While I was at it, I had the old ones checked out by a friend of mine...they where warped, severely. So yes they can warp, no "Special mechanic inspection for $$$$" needed.
 
#24 ·
It's good that you request more info. Let's see if we can dig some up that is truly convincing. But I take it from your comments that you're also willing to accept the word of people who have spent their careers learning and then sharing it.

I don't have another source yet, and I don't know if Bill does, but we should be able to come up with one or more.

But think about it for a minute, please. If the pad wears during braking and some of that transfers to the rotor surface, what happens when there is uneven friction? It creates hot spots that can make the pad material transfer differently. That will create a slightly thicker or thinner area that, when measured, looks to be warping. When the rotor is machined the metal the transferred material is on comes off, along with the transferred material. Your hypothesis holds water if only metal is removed, but was only metal removed or did pad material get removed as well?

Enough for now - I'll get busy when I have some time. It'll be this weekend (today is Thursday) before anything happens for me. I'm kicking my DSL to the curb in favor of returning to cable. 1.5 meg that runs at an average of 0.75 doesn't compare to 10 or 20 meg service. Cable is getting installed Friday and Thursday (today) is all I've agreed to pay for with my satellite TV and DSL.
 
#27 · (Edited)
But think about it for a minute, please. If the pad wears during braking and some of that transfers to the rotor surface, what happens when there is uneven friction?
A clarification is needed.
I did NOT say that pedal pulsation or an apparent warping can not be caused by other things. It can.

"Those guys" on the other hand, said that a rotor NEVER warps and I think that is a ridiculous statement to make.

The difference is easy to identify. Brake rotors are usually hard and shiny bright, like a mirror. When left out in damp conditions, they quickly show sighs of surface rust.......across the whole surface. Brake pad material is not shiny bright and not hard as steel. It also does not rust.

Also there are all kinds of "experts". In another forum, one member repeatedly stated that he had been a "mechanic" for 30 years. Turns out that he had worked in a tire shop all that time and was a tire changer.

Things are not always as they are represented. ;)
 
#25 ·
In my 24+ years of working on cars and trucks, I have seen rotors where they are thicker in one area and thinner in another. So, for whatever reason, this is referred to as "Warp", that is the term applied to it... That is the condition they where in, I need not explain the entire process to anyone on some computer as to how this was discovered. By the way, I give two #$!@s what someone calls a condition that is effecting my car...so long as it is able to be fixed. And as far as trying to spout off and show how smart you are and try to make me feel less than you...whatever...I have a real life away from this stupid computer forum BS. So essentially, if you have something helpful to say, that fixes my problem...cool, if not zip it.
 
#26 ·
I'm not gonna start or continue an argument. If you're offended by an opinion then I apologize for posting mine. How smart I am doesn't matter, nor does it matter how smart you are, or anyone else for that matter. What matters is what the truth is.

For instance, if the sky is blue and we're all arguing about whether it's red or yellow, then we're all wrong. I'm simply going to do some research to find actual facts.

If you're afraid of facts that might challenge your long-held beliefs then don't read them. But if you're certain of your beliefs, as it seems you are, then stand firm. As theories are presented you'll be proved right and I won't have an issue with admitting it. I just don't care who's right or wrong - I simply want the truth. Period.

On the other hand, if the facts support my opinion or something else entirely, then that is the info I'll use to improve my understanding. I only hope that you're big enough to see that it's possible that nobody is always right.

As President Lincoln said (paraphrasing), "You can fool all the people some of the time, and some of the people all the time, but you can't fool all the people all the time."

I'm not looking to fool people, and more importantly, I'm not looking to be fooled, either.

Look at my posts. I haven't called you any names. Please don't call people names or suggest something offensive when you reply.
 
#28 · (Edited)
Whatever dude, I didn't call anyone names...that is not my way. I simply feel that many a keyboard tough guy tries to place some meaningless BS about some technical info that they read about on almost every board I am a member of. Is the build up and reduction of the surface of the rotors referred to as warp....yes, I didn't say you said they don't warp. We call it a "butt load" not in reference to an actual butt, but, in reference to the measurement of the Butt... so warp is not that they have achieved some velocity exceeding the speed of light or that they look like a record left in the sun too long but rather the fact that they have uneven surface wear that, when viewed individually and not as an entire dual surfaced rotor, they would appear as somewhat "warped". I am sure there is no giant spider web over the planet, but we call the internet the "web". There are many terms and names we give different things in this world. Many could be conceived as wrong because of our individual opinions and ideals, but ultimately, they are just words.
Don't take things so personal, I never was attacking you, I don't even know you.:D

My favorite quote..."I enjoy your opinion, because it is so fricken stupid and not mine." - Dad -

This is not an attack...only my personal sense of humor. I mean no disrespect, but I am a War Veteran and biker with an attitude that prevents me from being socially acceptable (some say even naughty). Just kick me in the azz once in a while and I really get going.

Smile, laugh it off of whatever, but know this. I respect the fact that you stand up for your opinion, and the education you have attained by living your life. This is the last I will say on this matter.
 
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