Re: Rear Rotors on 5K

["Fred Munro" <munrof@isys.ca>]

Jim;

    I think the problem here is that the rear brakes don't work hard enough
to keep the rotors clean. If the front rotors get rusty after sitting for a
few days, they clean up after a few hard stops. It takes days of driving to
get the rear rotors clean. Winter kills my rear rotors - I go through one
set a year. I also service my rear calipers every fall - lube the guide pins
and clean & lube the pad carrier contact points.
    I don't fully understand what you mean by "from the inside out", but I
have noticed my rear rotors develop a shiny surface polished by the pads.
This surface looks like metal, but is actually rust and eventually flakes
away in spots leaving deep pits. If you leave the old rotors sit around for
a year and give them a good whack with a hammer, these rust "rings" fall off
and leave a usable metal surface behind. I actually had to do this and
re-use the old discs for a while last year when the discs on the car got too
rough to use and I couldn't get delivery of new rotors for a few weeks. The
old rotors actually worked quite well.

HTH

Fred Munro
'91 200q  258k km
-----Original Message-----
From: Jim Dhillon <jdhillon@cibc.onramp.ca>
To: Quattro <quattro@coimbra.ans.net>
Date: Friday, September 18, 1998 11:36 AM
Subject: Rear Rotors on 5K


>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..