My car has been vibrating lightly under braking when im braking from 50 to 30 then it stops and brakes normal. I recently changed my rear brakes with WMW rotors and red ebc pads, I am still in the bedding process of the pads and I am not breaking hard on them yet, but this has me wondering if the rotors warped or is it the fronts that are giving up already or something else, I haven't hit a curve or anything and I had an alignment done in January, with new tires put on during thanksgiving season.
Thanks for your help!

 

Same thing going on here. Had brake pads changed as part of MINI service in May. Brought car back in twice since, first time they said service bulletin for abs kept car for re-flash ect. Still happening. Yesterday after a decent amount of complaining they replaced front rotors. Hopefully this solves the problem.

 

I see a pair of front rotors in your future...

 

Lol. Non of you guys at the dragon looked old enough to know about Carnac the magnificent

 

I wish it were true.

 

Surprisingly, warped rotors are not as common as people think. What is common is contamination of the rotor surface. What happens is the some contaminet gets on the rotor, like while driving through a puddle of water, and some road oils or other contaminant gets on the rotor but it doesn't distribute itself evenly all over the rotor. The result is a dirty area and a clean area. When the pads grip the rotor, these alternating dirty and clean areas pass between the pads and because the dirty area is usually more slippery in comparison, the amount of braking force varies as the wheel rotates. This translates to what people perceive as a shimmy in the steering wheel because the braking force on one (or both) sides of the car is rapidly changing back and forth because of the dirty area on the rotor. Typically, there will be no movement or vibrasion felt in the pedal simply because the rotor is not warped. The cure is a thorough cleaning of both sides of the rotors. Sometimes a clean rag and lots of brake cleaner will do the trick. Sometimes it take some sort of abrasive. Usually, replacement is not necessary.

The other way it can happen when new rotors and pads are installed is that the brakes have not undergone a proper bedding procedure. Very few mechanics do this but it's critical to good brake performance. The brakes have to be gotten very hot (in a prescribed manner) so that some of the pad material transfers evenly to the rotors. If not done properly or not done at all, you can have areas on the rotor where different amounts of pad material have or have not been transferred with the same effect as I described earlier.

 

+1 on that.

For the most part warpped rotors is a myth unless you race your car on a racing track and have them get really really hot, I mean red hot.

Here is a great place for brake knowlede:
http://www.stoptech.com/technical-su...l-white-papers

And look at this page especially on warp rotors:
http://www.stoptech.com/technical-su...nd-other-myths

And this on bed-in:
http://www.stoptech.com/technical-su...and-procedures

A real bed-in actually involves depositing a thin layer of brake pad material on the rotor surface which is different than what people think of in having pads surface matting the rotor surface.
And to add to Martinb you can bed-in multiple times during the life of the pads and rotors which can be a way to fix your problem.

 

+ 1 on all you said. And Stoptech is an awesome source of good info! And yes, I forgot to mention re-bedding the brakes.

 

Umm, that's a little extreme. Warped rotors are not a myth if you drive your car aggressively on the street and then wash your wheels with cold water. I've seen that enough to know it's not a myth. Rotors with pad deposits may happen more often, but street-used warped rotors is relatively common.

 

I'd bet that it's not as common as you think. Most people, including mechanics, never check the rotors (most people don't even have the tools to do it) and simply replace the rotors cause they're so cheap.

 

Not likely. It's not a little heat and water cooling that's going to deform a relatively thick piece of harden steel. You would need to get it red hot and even driving aggressively I'd be very surprised you could get it red hot. Getting it red hot is the likelier way the tension of the harden steel would get released. More likely when driving aggressively and washing the car right after, you are creating pad material that bonds to the rotor unevenly giving the impression the rotor is warped. But that can be fixed.

But I'm far from an expert to tell you I know it all and I could very well be wrong

 

After having pads replaced and bringing car back 2x for steering wheel shake while breaking I did insist that they actually test drive and remove wheels to check rotors. 32 pt visual inspection stating brakes were good did not fix problem.My rotors were eventually replaced by dealer and no more problems. No answer as weather they were warped or not, but i will say this I did expect that the dealer at least check them and they seemed aggravated that i asked.

 

As common as I think? This is not dark magic. A car comes into a shop with complaints of rotor vibrations, you look at the face for evidence of deposits, if not you mic it (any self-respecting shop has the tool), and replace if warped. Your last comment about replacement is true: it's not cost effective to cut rotors anymore.

Oi vey. Does some other professional, who works on cars all day, every day, for years want to pipe in? Actually, never mind.

I've got to go over to the dental surgery forums and argue with a dentist about the cause of tooth decay.

 

Typical response by shops.

If the wheel shaked but there was no pulsing in the pedal, then the problem was likely contamination of the rotor surface or incomplete transfer of pad material to the rotors. Either way it's usually easily correctable without replacing the rotors. And I'd bet that the dealer never put an indicator on the rotor to check runout.

 

It is "dark magic" to more mechanics than you might think. I'll bet that a large percentage have never even heard of bedding in pads and rotors.

Note: you don't use a micrometer to check rotor runout. You use a test indicator. Sometimes a dial indicator.

And most of the time, customers complain of a shimmy or shake in the steering wheel when braking. Rarely do they complain of a pulsation in the brake pedal. If you have the steering wheel shake but no pulsation in the pedal, 99% of the time it's simply contamination of the rotor surface or uneven pad material transfer to the rotor surface. Both usually easily cured without rotor replacement.

I had the same problem on my Toyota 4Runner once...steering wheel shimmy without pedal pulse. At first I went to the dealer and they checked them and said the runout was within spec. Told me nothing was wrong. I said what about the steering wheel shimmy and they just shrugged their shoulders. Then, I pulled the front wheels and thoroughly cleaned both sides of the rotor with clean rags and brake cleaner. Problem solved. Until, that is, a few months later and after one of fall's first rains, I drove through a big water puddle (lots of oils and dirt in the water from the first rains), the shimmy came back and I had to clean the rotors again.

Same problem with my wife's Murano. From time to time, some wheel shimmy would show up. Probably some contamination. All I had to do is get them real hot, like when bedding brakes, and it would clean off the contamination and essentially re-bed the pads and rotors and all would be good.

Like I said, warped rotors that are out of spec are not that common.

 

Oi vey, as much as you want . . . . I stand by what I said with the knowledge I have acquired so far . . . and just as I said I'll gladly accept being wrong when common sens explanation is provided. Sarcasm won't help anyone . . .

I've work on my car quite a lot and I have done a much much better work than the professionals have been able to help me with when I had brake vibration and performance problems BUT after having done much research.
I don't mean to offend the "professionals" but a lot of shop don't spend a dime of energy studying the problem when it is a lot more lucrative to sell you parts and services within the time they have. This is when quick but possibly false assumptions are spreading. It gives the professional some easy justification for their client. I don't blame them. Their business isn't science education. They've got to fix cars and quick. No time to waste...

 

I've seem rotors "warp" just from guys blasting wheels on after a tire rotation without using torque sticks or a wrench...

 

Yes, I'd have to agree. That is one way it can happen . . . though admittedly I've never quite understood how the rotor hat can deform with such a tall wall...

 

I was having the same issues as the original poster and i replaced my rotors and the problem went away. now the car stops perfect. i totally think bad rotors can cause the shuttering when braking.

 

Actually my dealer only tried to sell me a coolant flush when I complained of the shimmy in stealing and pulse in pedal the third time. They were reluctant to do anything test drive remove wheels ect.

I am not a mechanic by a long shot but I did spend most of my childhood and teen years working at my dad's shop. Enough to know that coolant flush was not the answer. Rotors swapped out no more problems.

Shame really almost had my fiancée convinced we needed brembo kit


Oh and helix - sarcasm is always welcome around us.

 

Martinb, in the profession, any precision measuring device is called a mic. Nobody says 'test indicator'. Your implication is that I, by not calling it a 'test indicator', am ignorant about brake rotor warping vs. deposit as a cause of pulsation in the steering wheel. This is nonsense.

To say that most professional mechanics "have never even heard of bedding in pads and rotors" is indication of your insight into the car industry. Perhaps you are claiming that for effect, and don't actually mean it, but I have to take it at face value that this is your opinion. I can guarantee you: most professional mechanics have heard of bedding pads and rotors.

You did say that before, and once again, I will have to respectfully disagree. It's clear that you are somebody who has some experience in working on cars. Maybe you have friends in the industry that tells you anecdotal things about common mis-diagnoses, and this is where your conclusions come from. If your point in this debate is: sometimes, technicians mis-diagnose rotor deposits as warped rotors, I agree. If your point is what I have highlighted above, I disagree.

The difference between your opinion and mine is: I'm a professional, and I'm good at what I do. I see one to two dozen cars a week, and I've been doing this for decades. You'd probably kick my a$$ in any number of other arenas when it comes to knowledge, but not this one.

It wasn't sarcasm, it was exasperation. I usually don't take the bait in this kind of internet opinion-a-thon, but I was caught hook, line, and sinker. The Oi Vey was more at myself for even getting involved.

 

Right, you use a micrometer to check disk thickness variation.

Dial indicator for runout (as well as hub runout.)

Dear Martinb... please follow along with this lab, this is what my students do in the industry who go on to work for such lame car makers as BMW, Audi, and Tesla.

This is only one lab out of an entire semester of what my students go through with a 16 week long brakes class. Keep in mind, that brakes is split into two college semesters...

 

Hey man, I'm not the kind of guy who likes to pick a fight on forums. 99% of the time it provides nothing to the OP.
It wasn't the Oi Vey, but the dentist comment I was referring to about sarcasm... And to be honest I though it was funny anyway . . .

I understand your position and opinion. Personally all I care when going on forums is NOT to be right all the time but rather to help when I can and learn when I'm new to a problem. I like educational debates and as much details on the subject I can gather to correct my own knowledge. I enjoy different perspectives but words are too easily miss interpreted

So in the end, I might have been too quick to reply anyway. I'm very new to this forum and I should respect that, seat back, and relax

 

Far too often people equate high post counts on a forum with knowledge. That's just simply not true.

As to the original purpose of the thread... You've already been pointed to the StopTech pages on bedding in pads so you should know that there isn't really a "break in" period for brakes. Use them hard right away and let them cool off gradually.

The only time I've personally seen warped rotors is from people who come in from auto-x runs or track sessions and promptly set their e-brake and walk away from the car. Fortunately in the mini the rear brakes don't get so hot but for other cars the brake pad touching the rotor gives the rotor a heat sink so that portion of the rotor cools faster than the other parts. People have tried to re-bed their brakes after and had no luck. Replacing the rear rotors cured the brake pulsing.

 

Of course. "Bad" rotors are usually the only cause. But the point Iv'e made earlier is that a large percentage of the time, you can take care of the problem without replacement. FYI.