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      12-06-2012, 11:30 PM   #4
Private First Class

Drives: 2007 E93 N54
Join Date: Sep 2011
Location: Lexington, KY

iTrader: (0)

Originally Posted by Tim603 View Post
Hey Guys so I got the geomet slotted front rotors for my car and installed them about 1500 miles ago. I used the existing cool carbon brake pads on my car since I only installed them like 3000 miles prior to the new rotors so there was plenty of life left on them. Well they have been great thus far and now I have steering wheel wobble when i apply 40% or more brake at speeds around 30-70mph. Someone told me that it could be carbon buildup on the rotors making the surface uneven and that some heavy braking could help burn it off? Any suggestions on what I should do. Ive contemplated buying new brake pads to see if that will change anything. Thanks for any advice.
It does sound like you may have a high thickness variation (TV) of the brake material on the rotors (the "transfer layer")that can result from not properly bedding in the pads to the new rotors. This can continue to get worse, as the pads continue to deposit more material on the "high spot" and skip the lower spots, much as a small dip in a road can quickly become a pothole.

The answer is not to brake heavily - the transfer layer is built up when the pads meet the rotors at high temperatures, thus resulting in more pad material being deposited. In light use, when the pads don't heat up and transfer material to the rotors, it's actually possible to "unbed" the pads from the rotors, since the stopping forces are more friction than adhesion, and the friction burns off the transfer layer from the rotor. For street pads this "unbedding" doesn't usually result in a loss of stopping power, and a few hard stops will re-bed that pads.

I suggest a few gradual "rolling stops" from 60 down to about 10, do not let the car stop with the brakes applied. Do this several times allowing the brakes to cool between stops by driving at a steady rate of speed without using the brakes. Then follow a normal bed-in process (see the articles I linked above) and see if that helps.

2007 E93 N54

Last edited by andrew_b; 12-06-2012 at 11:36 PM.