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!

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.

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!

It sounds like the rear drums the way you described it.
There are no press on rotors, it may be stuck on and appear to be pressed on and you may need a BFH to beat the rotor off the hub, but they are not pressed on.

If the Steering Wheel shakes, Its the Front Discs. They are more likely to get warped than drums. Since they do most of the stopping. And have the greatest amount force applied to them.

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.

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?

OK. I'll go with the front rotors. Do I need to replace the pads as well? If the rotors were warped, would they have not worn the pads unevenly?

That's a judgment call to make when you take it apart. If the pads are 50% or more material left I'd run um. If less then that replace. Be sure to grab a can of parts and brake cleaner for those new rotors.

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.

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.

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.

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.

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.

Had it happen. Coasting from 90 for an upcoming stop sign. About 65 when the rear wheel passed me. Thank God no cross traffic at the intersection. What a ride!

My Maxx is doing the high speed shimmy too. I will try replacing the front rotors. Thanks for the info fellas

My Maxx is doing the high speed shimmy too. I will try replacing the front rotors. Thanks for the info fellas

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.

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

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

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...

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.

they where warped, severely. So yes they can warp, no "Special mechanic inspection for $$$$" needed.

The rears can warp too.
There is nothing special about jacking up the car, spinning the wheels and applying the brake lightly to see which one is actually causing the problem.
If you did not do that, then you just got lucky.

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

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...

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.

The rears can warp too.
There is nothing special about jacking up the car, spinning the wheels and applying the brake lightly to see which one is actually causing the problem.
If you did not do that, then you just got lucky.

Guys, let's all be civil, especially you, Rukee.

Brake discs DON'T warp! (http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml)

That link above is to a site that has more knowledge than anyone on this forum (to the best of my knowledge) about brakes. And Bill was absolutely correct when he said that rotors don't warp. (Disclaimer: Read the article. At the top it says they can, but only if installed incorrectly, not due to braking.)

If you have a real desire to learn and understand how things actually work it will make sense and you'll be miles ahead of all the others who say the oft-repeated phrase, "the rotors are warped".

If you want to comment, take the time to educate yourself, and take the time to show some respect to others who share truth with you. Bill did just that and his reward was a comment inferring he was ignorant.

If you click on my screen name and find other posts I've made you'll see that I'm not always right. The difference between me and some others is that I can admit when the information shared with me is a better understanding than I had coming in, and I leave with a better understanding. How can any of that be bad?

If you choose to stay in the stone age, go ahead, but please don't start spouting opinions that you haven't researched or for which you have only partial knowledge.

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...

Go to the StopTech brake web site and read their Technical information. They are far better experts than I am and they say there is no such thing as warped rotors. Here is the link to the white paper: http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml . As for uneven brake deposits some times you can see them and sometimes you can't. All brake pads deposit a layer of material on the rotor. It is called a transfer layer and is needed before the brakes can work properly. Sometimes that layer is deposited unevenly and will cause differences in friction so a pulsing will be felt in the brake pedal. Uneven deposits are usually the reason for lateral thickness variation. A bad wheel bearing can cause a long brake pedal due to piston knock back (difference between that and a low pedal) but it can also cause pulsing brakes as can a wheel that isn't mounted correctly on the hub. Sometimes all you have to do to get rid of a pulsing issue is to pull the wheel, clean the hub, make sure the wheel is flat against the rotor and the rotor is flat against the hub flange and the pulsing magically goes away.

Bill

Brake discs DON'T warp!


OK, fine. I'll play along.

When you take a brake rotor and run a micrometer along the surface and the surface is not true anymore, what DO you call that if not warped ??

And then when you machine the surface so that it is true again (turn the rotors) and the material that comes off is metal, what condition are you "fixing" if not one of warping ??

Is this a problem of semantics ??

I have seen a lot of "warped" brake rotors over 50 years and I don't know what else to call it. I don't remember, however, a single case where turning them solved anything long term because it just covers up the real problem temporarily.

Go to the StopTech brake web site and read their Technical information. They are far better experts than I am and they say there is no such thing as warped rotors.

I read.

This statement caught my attention:
"This has been going on for decades now - and, like most things that we have cast in stone, the diagnoses are wrong."

Just EXACTLY who authored this "information" and what are their qualifications ??

It looks pretty amateurish to me; much like a lot of other self-appointed Internet experts who, above all else, just want attention.

They are in effect saying: The entire automotive industry.....engineers, techinicians, mechanics......for 50 years or more have been fooled into thinking that brake rotors warp........ALL of them. They are all stupid but WE are smart and have figured that they are all wrong. Really ??

I'm sorry but I'm not buying it. I think we have another "urban myth" in the making.

How about another reference to support that claim ?? One that doesn't refer back there, that is.

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.

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.

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.

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. ;)

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.

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.
Bull. First if you are ASE current then you should know that torque sticks have no longer been recognized by ASE for several years!
As to the drums, there was a time when the practice was to arc the shoe to mate the drum. This gives maximum surface contact of shoe to drum. As drums wear or is turned, the contact patch of shoe becomes smaller, but will increase with wear. And they will wear quicker because initially all the wear is at that small spot. And that also concentrates all the heat in that one small area as well.
It is best to find new drums that have a minimum of metal removed during the finishing process. That is they are at the minimum inside diameter specification. And then try to find shoes that have maximum contact with thick linings. I have personally arched shoes increasing new contact by double.
I am not familiar with you Malibu drums, but I have seen drums where it seemed the hub was an integral part.
The vibration in steering is definitely front end. The pulling is a caliper sticking. With the age of your vehicle, I'd recommend flushing all of the old brake fluid out with fresh new. Brake fluid absorbs moisture from the air and that small amount of water starts corrosion which will cause caliper pistons and the pistons in the wheel cylinders to stick, ruining your brakes or failure.
Depending upon how long you intend to keep vehicle, to some degree, you might consider all new parts. Hardware kits are not expensive but will add to total cost. Personally I'd rather rebuild calipers than buy rebuilt. There is no knowing what condition they were in before processed and heavy sandblasting will wear away metal at slide surfaces causing a loose fit.
A few cautions if you are not familiar. Never let parts hang by the brake hoses. It can cause internal collapse and loss of braking.
Careful not to damage any rubber components, seals, etc. Apply disc caliper/silicone grease where appropriate, never to any braking surface. A honing stone attachment to drill may be necessary to resurface steel internal surfaces. If you have steel pistons, not used much anymore, you may need some very fine emory cloth to remove corrosion. Any deep pitting may require replacement. Plastic or fiber pistons may be available for replacement. They don't pit.
For long term reliability, perhaps regrease slides one a year and flush fluid at least every three years. Old Mercedes spec was every two years. Fluid and labor for them is cheaper than new parts. If you are a DIY the same may apply. Certainly cheaper than new calipers and wheel cylinders every few years.
Torque everything to spec. and it will be like factory new.
A whole lotta gotcha's not mentioned and good luck.

OK, fine. I'll play along.

When you take a brake rotor and run a micrometer along the surface and the surface is not true anymore, what DO you call that if not warped ??

And then when you machine the surface so that it is true again (turn the rotors) and the material that comes off is metal, what condition are you "fixing" if not one of warping ??

Is this a problem of semantics ??

I have seen a lot of "warped" brake rotors over 50 years and I don't know what else to call it. I don't remember, however, a single case where turning them solved anything long term because it just covers up the real problem temporarily.
I don't know what to call it either if it is not warped. Double-sided rotors, those that have air vents in the middle can be out of balance. This is corrected by adding weight and is most often done by putting expansion pins into the vented area. I've seen some new rotors that don't have them and I'd be suspicious of whether they were spun balanced.
Motor Week and another show of similar title did pieces on warping several years ago. No one reason of it was not properly torqueing. Back then Torque sticks were allowed.
Rotors are not a hard steel or they would not function properly. And the variance before you sense it is an extremely small amount, fair less than a hair. As to being able to permanently cure by returning, their is such a possiblility which I have recognized. And to minimize that, when I had such problems in the past, I'd retorque wheels to proper spec and then drive like that for a couple of weeks before dismantling. That is attempt allowing the metal to relax a bit back to its original form.
When nuts are overtorqued and to some degree under-torqued it causes movement of the metal at that location. It would be like hitting the rotor with a heavy hammer at the stud location and then clamping it. Over time that compressed metal spreads its forces outward causing very slight deviations in the surrounding areas. And that is all it takes. The process is accelerated by heating and cooling and maybe accelerated by driving through water which is what all mechanics used to claim was the reason. Not their fault that is. BS.
So the mating surfaces need to be true, that includes the machined surface of aluminum or just steel wheels which will take on that warpage with time. This is another good reason to always mount a wheel back to the same pattern as it was removed. Sort of makes you wonder if rotating is ever a good idea.
I can personally attest my anger at a shop that sold then rotated my tires. A very thorough brake job I had done was perfect until about 2000 miles. I even did the breakin thing. It was time for rotation and I asked them to torque wheel nuts. Within 600 miles the rotors and drums warped. I went back to them and salesman trying to spoof me that they always torqued the nuts. Through the window to service bay was a mechanic mounting wheels with impact wrench and all I had to do was point and say, "You do?"
But still the correction was turning of brand new components. If it ever happens again, I will demand new.
BTW, impact wrenches are the reason wheel studs are damaged and broken. Yet they will try to charge you for replacing. My opinion, impact wrenches should never be used on wheels unless they are specifically designed for that vehicle they are being used on.