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      12-07-2012, 12:31 PM   #6
Tim603's Avatar

Drives: 2007 335i E90
Join Date: Feb 2012
Location: North Canton, OH

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2007 335i  [0.00]
Originally Posted by andrew_b View Post
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.
I will definately have to try this, I will let you know how it goes. Also I called ECS tuning and they said roughing up the pads with some sandpaper could also help, what do you think about that?

Originally Posted by David1 View Post
The cool carbons are your problem.
I think I would have to agree, red stuff or Hawks in my future

Originally Posted by SmellyGreek View Post
Sounds like you didn't properly bed the pads to the new rotors. Depending on the pads, the procedure may vary a little but the general concept is to do a series of 60 - 5 MPH hard stops with a few minutes of driving (while minimizing the use of the brakes) in between to let the brakes cool down. This ensures an even transfer of pad material to the rotor to prevent brake pulsation at high speeds.
Where would you guys recommend I do this, I need to find a place that doing this would be legal (or not completely obvious that Im breaking the law) and I cant think of any places. Highway is obv not an option b/c of how slow i need to get.

Thanks for all your help guys