[urq] V8 Brake swap for UrQ - saga continues..

[kleinbiker1 at aol.com]

I currently have the 5KTQ dual piston calipers on the front of my 85 UrQ along with the stock MC, and it works fine.  Incidently the MC is the same one as in the 5k and avail pretty cheap as a rebuilt from NAPA.

Chris






-----Original Message-----
From: Ben Swann <benswann at verizon.net>
To: 'Mark Rosenkrantz' <speedracer.mark at gmail.com>
Cc: urq at audifans.com; quattro at audifans.com
Sent: Sun, Nov 7, 2010 9:43 pm
Subject: Re: [urq] V8 Brake swap for UrQ - saga continues..


Thanks for the reply - I suspected something like this.  If that is the case, 
hen
robably the proportioning valve won't work, except to divert all braking to the 
ront.
 still probably ought to install one.

here are two different master cylinders for the early UrQ.  I ordered the 
arlier 443
11 021 (23, 81X19/17) . Should I have ordered 447 611 021 (25,40X18/18) ?  I'm 
ot sure
hat the numbers mean exactly, but presume the bore size is larger in the later 
ersion.
aybe there is another one I ought to get - perhaps from a different car.

 originally tried to fit the V8 Quattro Master, but it did not fit the booster 
 which
rompted me to open up the booster (idiot!) thinking the plastic retainer was a 
pacer
leeve.

 could really use some help on this - I want to stay the course with the V8 
rakes and
ltimately put the Porsche monoblocks in front.

en
  _____  
From: Mark Rosenkrantz [mailto:speedracer.mark at gmail.com] 
ent: Sunday, November 07, 2010 9:14 PM
o: Ben Swann
c: urq at audifans.com; quattro at audifans.com
ubject: Re: V8 Brake swap for UrQ - saga continues..

en,
Without doing the calculations, I suspect you have a swept area problem. Going 
o
bigger brakes" often leaves a long pedal.
hen doing brake modifications, the size of the new caliper pistons have to be 
aken
nto account when choosing a brake master cylinder. With no other changes, when
ncreasing piston size, often the result is a master cylinder primary piston 
hich will
weep right past the correct operating area and either bottom out on the 
econdary
iston, allow cross circuit hydraulics, etc. I'm tired... hardly the right term 
ut I
ust got home after frostbiting the J-24 all day.
rakes are too often thought of as individual pieces and not as a system. Big 
istake.
rembo, Stoptech, etc.... they're not taking a single caliper and making 
ifferent
rackets. The caliper bodies might be the same across different applications, 
ut the
iston bores sizing is application specific for, bias, area and to minimize pad 
aper.
ake for example a Stoptech application for a 2000 A4 bodied car. All use the 
ame
aliper body, but the piston size and radio is different for a 1.8T, a 2.8, and 
he S4
o match the spring rates (for bias) and master cylinder volume.
 couple of remedies: A proportioning valve might be enough. Properly sizing the 
aster
ylinder. Sleeving the calipers with smaller bore pistons.
ood luck,
ark Rosenkrantz
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