[urq] V8 Brake swap for UrQ - bad info worse than no info.?

[Steve Eiche]

  The master cylinder listed for the RR (20V) ur quattro that used the 
V8/urS rear brakes is part number 447 611 021, with a 25.4 mm(1") bore 
and 18/18mm stroke.   The 10V ur quattros used a master cylinder with 
23.81mm bore and 19/17mm stroke.   The 20V master cylinder is also used 
on 100/200q Avants with a certain rear brake package.   It is a "long" 
master, NOT like the short one used on the V8 or 20V 200q or ur S 
cars.   Also note that the RR ur quattro used a different brake booster 
(same as '89-'90 CQ and 90q 20V) which is very different than the 10V ur 
quattro brake booster.  Also note that proportioning valve is also 
different on the 20V ur quattro   I can confirm from experience that 
with the right parts it all fits together quite nicely.  Some people may 
have used the V8 or 200q 20V aluminum master with the vacuum assist 
power brake conversion, but that the only way I can see one of those 
working in an ur quattro.   Most people just install the bigger rear 
calipers with the stock ur quattro master and call it good.  YMMV.

As for the "rebuild kit" for the brake booster, those can be put 
together at a local shop that supplies O rings and seals.   That is how 
all the kits that I am aware of can to be.  I know a couple of guys here 
in Denver got all they needed from Rocket Seal in Denver by matching up 
the old O rings and seals.   As long as you don't lose any parts or 
damage the interior surfaces and you get everything in in the right 
order, there is no reason that you can't put the brake booster back 
together again.

Steve