Rear Rotors on 5K

["Jim Dhillon" <jdhillon@cibc.onramp.ca>]

Does anyone know why rear rotors seem to rust from the inside out on Audi
5KQ's (perhaps others too?) The fronts don't have this problem but I have
owned Audis since the 70's including at least 5 80's 5K models and all of
them have this problem (plus the rear calipers tend to jam up too.. the
problem has been more pronounced on the right rear than the left rear.. I
have even seen this on my 1990 Audi V8 which has the vented rear disks...
machining only reveals deeper rust pockets!
Jim D..