Hi

I have a very strange brake problem on my 850 that neither I nor the mechanic that works on my car can figure out. I had new front OEM size cross-drilled rotors installed along with some KVR brake pads about a month ago. I broke them in, as instructed, and as far as I can tell, they work wonderfully and very smoothly. But recently, I've taken a new route to work that has a steep descent that requires a good amount of braking and that is when I first felt some vibration. It only occurs on this stretch of road and I have yet to duplicate this vibration on any other surface and/or road around where I live. I don't feel the vibration particularly in the steering wheel or anything, just some noise and then the whole car seems to quiver/vibrate--can't even accurately point out that it is even the front brakes causing it. And it only occurs at very very low speed, by my accounts, the noise & vibration kicks in at the last 2 to 3 seconds of braking and by that time, I've slowed to practically a crawl. Today I had my mechanic re-torque the lug nuts (to make sure they are torqued within spec) and visually inspect the brakes and he could not find anything at fault. I hope the rotors aren't warped and my mechanic assures me that warped rotors would be more obvious and would happen at all speeds. Can anyone offer me some help on this one?