I recently heard a Car Talk episode in which the caller had a problem with his car wobbling or vibrating while he was braking. The conclusion was that the rotors were warped. A quick google search would confirm that this is the most probable source of the wobble, but I’m not sure if it is correct for my problem:
I drive a 2002 Subaru Impreza WRX. For quite a while not the steering and what feels like the whole car wobbles or vibrates when I brake. This is imperceptible at speeds under around 45 mph, but at high speeds it is VERY noticeable. It seems especially bad if I am going around 70 mph and lightly applying the brakes. The wobble does not happen unless the breaks are applied. So, warped rotors right? So I decided to check them and see if they are warped. I took both wheels, calipers, and rotors off my car and inspected the rotors. My initial impression is that they looked as good as when I bought them. Of course an eye-ball diagnosis would not sufficiently answer my question so what I did was compare one rotor to the other. I put them together rotor on rotor to see if I could find any variation in shape. I figured that if one rotor was flat, while the other was warped, it would be noticeable. If both were warped, than the difference should be exaggerated. I did this multiple times to make sure I wasn’t missing any warp or distortion. So as far as I can tell, ther aren’t warped. Another thing that I noticed, however was the brake pads. They were in good shape for the most part, but the corners/ends seems to be worn of at an angle about a quarter inch from the edge. I reassembled everything and when I drove the car, the wobble was gone. Now after about 15 minutes, the wobble returned. And now I need help figuring this out.
Here are my Questions:
Is my method of figuring out whether the rotor is warped reasonable? am i missing something?
Why would the edges of the brake pads be worn down that drastically?
Could the wobble come from something else? Struts? wheel bearings? bent wheel? If so, how can I diagnose/test which one it is?