Rear callipers - Was: 85 q turbo coupe wr engine maintenance

[Paul Heneghan]

From: <isham-research.freeserve.co.uk at pop.pol.net.uk>
Date: Sat, 16 Sep 2000 18:47:13+0000

>>> Separate issue... I provided chassis no 85ZFA900864 and asked Lomond
Audi of
>>> Glasgow to order me the seals to rebuild the rear calipers on the car.
They
>>> provided two sets of 443 698 671. Several people - myself included -
have been
>>> shipped kits that don't obviously fit - the piston seal is too small.
>> Well, I am in possession of TWO KITS of seals that are way too
big.....want
>> to swap?
>> The diameter of the seals looks about two inches.
>> Work phone 01698 422900 home phone 01357 520684
> Can you give me the exact diameter of your rear caliper pistons in mm?
> I'm hoping to hear 60 rather than 54.

My 80q (85ZEA......) and both Avants have 36mm rear pistons.  It's embossed
on the casing in 1/4" numbers (and I measured it anyway).  Why on earth
would you need 60 at the rear?  High speed reversing???

While on the subject of callipers, I eventually managed to dismantle mine -
the one that had handbrake problems.  The problem I had was that the
threaded shaft that transmits the parking brake action to the piston was
seized.  My solution in the end was to drive a nut with a different pitch
(the shaft has a very coarse pitch - I couldn't find anything that would fit
it except for the piston and I didn't want to wreck that) onto the shaft,
then I was able to put two screwdrivers under the nut and lever the entire
shaft out of the cylinder.  The mini piston at the base of the shaft was a
bit corroded as was the mini cylinder it fits into.  The o-ring wasn't
exactly pristine either.  I cleaned the whole assemble as best I could, and
reassembled using the original seals just to see if it would work.  The
parking brake was fine, but brake fluid pissed out of the seal at the top of
the parking brake mech.  Obviously the corrosion of the piston at the base
of the shaft coupled with a dodgy o-ring was incapable of giving any kind of
seal.

Once again, my old dismantled Audi came to the rescue.  The rear calliper on
that was in excellent condition.  I reckon I've used about GBP1000 of bits
off that car already.  The only downside is that my wife and the neighbours
weren't very impressed with the slow dismantling that took place over a
couple of months!

Paul