Originally Posted by
CCrew
Give that man a cigar. Yes, the XT brake surface is different than the Avid, so much so that given certain configurations the brakes are actualy hitting the center web of the rotor.
And sanding them was certainly not a good idea. Rotors are blanchard ground to assure a consistent surface finish.
The front brake generates a sound due to the pad hitting the center web. The rear brake "grab" is at a regular point of wheel rotation, much lower frequency than the faint pulsing noise on the front that corresponds with the 8 supports on the center web.
Sanding was my cleaning device of last resort, since no solvent had done the trick. Either way, the sanding/alcohol cleaning produced absolutely zero change.