Thanks to MBtech21 for a very good explaination.

However, I have a few questions...

MBtech21 wrote:
< Second one is what tom was talking about- actually, its not pad deposits that usually cause this- it's the pad ripping material from the disc. Usually occurs when the car sits for a while- with the metallic materials in pads now, it is a given that they will corrode to the rotor with very little time/moisture involved. You jump in the car, put in drive and RIPPP..... away goes some rotor surface(and pad surface)- this can be driven out of the car, at least on an MB, by braking hard, or using the sanding pads, >

Note: 11,000 miles on 4 new rotors & pads. After my 94 e320 sat for about a month, I discovered an accumulation of material on both sides of both rear rotors from the leading and trailing edges of the pads. I hand sanded with 400 grit until the disk surface feels smooth. After about 500 miles of city driving, a slight thumping still is present.

Is it more likely the rotors or the pads?
Why just the back and not also the front?
About how may miles would it take to drive/brake it smooth?

Until 1964, my father had a 2 bay "Gas Station" - the kind that fixed most anything and have been converted into mini-marts. He taught me; mount the wheel, attach each lug nut in a star pattern with a speed wrench (didn't have an air gun in those days) and then again in the star pattern, use a 1/2" breaker bar to tighten each to a squeek.

Other than using a torque wrench instead of a breaker bar, isn't this still the prescribed method?

Bob