Why does my car wobble when I brake?

Popular Mechanics

(Photo: Nick Ares | Flickr)

(Photo: Nick Ares | Flickr)

Q: I have a 2009 Lexus ES 350 with 55,000 miles on it. Lately when I hit the brakes, the car trembles. I looked at the front brake pads and they're still good. What could be the cause and how should I fix the problem?

A: It sounds like you have a classic case of warped rotors. Braking removes material not just from the pads, but from the discs as well. As rotors get thinner, they are more susceptible to warping because of the heat generated during braking. Although sometimes you can't see any irregularity, that's what is causing shudder when a caliper clamps down. You can solve the problem in one or two ways. Remove the brake rotors and have them turned at a brake shop. This is a machining process where the surfaces are smoothed using a special lathe. First, though, the shop will measure the thickness of the rotor. If it's too thin, legally they aren't allowed to turn the rotors.

The other (and probably more time-effective) option is to buy new rotors and replace your old ones. It's a good idea to swap out the pads at the same time. At 55,000 miles, if you haven't done a front brake job on your car, you're not far off from having to do one anyway.

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