[s-cars] [urq] S-Car Brake system conversion- Read- no more PSpumpintegration <question>

[Scott Justusson]

Late on this one, and probably the first to put Big Reds on an Audi
Quattro 15 years ago (5ktq no less).  The key in all these responses is
"All else being equal".  Specifically, all else isn't.  Ex-TRW Brake
guru Keith Maddock and I shared a very interesting discussion almost 8
years ago about G60 brakes.  We agreed quickly that the caliper and the
rotor are not the problem with G60's.  The *CARRIER* is.  It flexes,
warps, has crappy pin design, and has unequal pistons in the caliper to
help fester the problems.  The caliper and piston area itself is quite
large, and the rotor is well vented and quite beefy.  The pads have the
same swept area as a 95 M3.

WRT pedal feel, a lot of 'unequals' can make a difference.  On an OEM
Textar pad for example, the antisqueal plate is 1.5mm thick.  Several
aftermarket suppliers don't use one at all.  A Colemann Rotor is 32mm
thick (what I used for the Carl J/Scott J kits.  An A8 rotor is 30mm
thick.  So, a guy with Big Reds with A8 rotors and aftermarket pads will
have 2.5mm more Caliper piston travel than another guy with Big Reds
with Colemann Rotors and Textar pads. Both at "NEW" spec!

IMO/E the advantage to BBK is in the non-'floating' design advantage
taking out the warpage issue inherent to the G60.  That said, there are
several floating brake calipers that give phenomenal performance with
less piston area than a G60.  The ATE single piston caliper in the
A4/late 200tq10v come to mind.

I like G60's myself, and would put a good set of G60's against BBK in
street driving stopping distance anyday.  IMO, their problem is heat
deforms the carrier assembly badly, and that makes them a poor choice
for track or multiple stops.  The BBK can solve the heat issue well.
They also increase reciprocating mass quickly, which diminishes their
ability to 'decrease' stopping distances over the G60 setup.  

The debate on the physics seems silly to me...  Too much that's not "all
else being equal".  One of the best brake kits I ever tested was a
Brembo lotus esprit 4 piston caliper clamping a stock 200 rotor, all
under 15x7.5 lightweight BBS wheels.  Low reciprocating mass, a stock
Audi 45USD rotor and aftermarket "premium" pads from Murrays Auto.

The second best sits on my 94 Landcruiser.  Bone stock 4 piston fixed
calipers, 16in wheels, 3 channel ABS it stops the 4700lb beast in a
rag-documented 128ft.  I have my doubts any S car could do that in any
brake trim.

Hey, what do I know?  I like UFO brakes too...

Cheers

Scott J
BBK instigator emeritus