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I have a 2002 Kia Spectra. We have replaced the rotors 3 times, but prior to doing that we were having problems with our back brakes. The mechanic we were going to said nothing was wrong with the back brakes, but to just keep driving the car. We kept experiencing problems with the back brakes and decided to take it to another mechanic. He found the back shoes were worn thin, the drums needed to be replaced as well as the wheel cylinders.

Once all that was taken care of, the car started to shimmy again when applying the brakes. Took it back to the mechanic who replaced the back brake work thinking they may need adjusted, but it wasn't that. The rotors were warped he said. So we went back to the first mechanic who did the front brake job. He replaced the rotors. A week later the problem came back. We had them checked again by the mechanic who did the back brake job thinking once again it could be the back brakes. He said no, it's the front rotors again. He checked the calipers and they are not sticking. He checked the brakes hoses and says no leaks or problems there. Master cylinder is OK.

Got a third opinion today: rotors warped! This guy today says unmatched rotors and cheap brake pads. So the mechanic I figure has been putting on cheap parts. They are over heating and causing the rotors to warp. Does this sound logical or far fetched? Help!!!!

  • Check out this thread and see if it doesn't seem logical. I'm betting the front brakes were not bedded properly. – Pᴀᴜʟsᴛᴇʀ2 Feb 20 '15 at 20:57
  • Rotors warping right after installation is a myth. Either they were eccentric (defective) to begin with, installed crooked (yes this is possible), or were subject to improper break-in. The shimmy feeling is from uneven friction material distribution over the rotor, which may or may not be due to an eccentric rotor. – kmarsh Jan 7 '16 at 1:01
  • @kmarsh Take your other answer and jam into this one. The question will get answered, the stats will get better for the site and you'll earn points :) – DucatiKiller Jan 7 '16 at 3:44
  • Done! I like points. :) – kmarsh Jan 7 '16 at 14:36
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What is passed off as a "warped rotor", and blamed on the user running through a puddle after heating the brakes, is a myth.

The shimmy feeling that comes from brakes is usually due to uneven friction material build-up on the rotor. This transfer from pad to rotor is supposed to happen, indeed it makes the brakes work better, which is why brakes function better after break-in. However when it happens unevenly, it produces a shaking or shimmy feeling. Why does it build up unevenly? There are three major reasons.

  1. Rotors were eccentric when new. It takes time for the pads to wear a bit and the friction materal build-up to occur. What's more there is lubricant on the pad ears, pad backs, caliper pins, etc., that happily allow movement on a new brake job (hopefully), but this lubricant gets washed off over time.

  2. Rotors were of uneven thickness when new. The results are the same as #1.

  3. Improper break-in. Typically this involves heating the brakes up, then coming to a hard stop and leaving the brakes on hard. This puts a "pad imprint" on one part of the rotor, that will continue to catch more pad material and build up... creating the shimmy feeling.

Since learning all this, I have eliminated all brake shimmy in my personal fleet by doing the following:

  1. Checking all rotor widths with a micrometer, and all installs with a dial caliper for runout.

  2. Proper and complete lubrication of all contact points. I use Sil-Glyde, but there are other purpose made lubricants that will work.

  3. During break-in, avoid leaving the hydraulic brakes on after a hard stop. Coast, use the handbrake for the final stop, whatever it takes. (It is the front rotors that do all the work and heat the most).

Don't take my word for it, listen to the expert, here: http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

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