[200q20v] Re:Caliper Piston Extension Conclusions

[QSHIPQ at aol.com]

...  Ok not my last, I have to spell it out, mostly for Hap, er, Mike.

The original mess started with a post from MGW that clamping a 30mm rotor
with a Big Red caliper could be "risky" (see 11-08-01 "RE: Caliper extension
differences" from audi@ prospeedmktggrp.com), a 32mm rotor is proper and less
risky.  This information was "supported" by using a stock Big Red Caliper and
PF "Z" pad measures.

Yesterday, I mic'd some Big Red application pads (PF Z's, Porterfield
AP594-R4, and factory Porsche 993.351.930.01<textar T428FF).  My conclusion
is that aftermarket pad thickness variance is more than the 2mm rotor
difference, and it is this PAD THICKNESS VARIANCE that creates any risk MGW
proposes.  Conclusions:

*  A Big Red Caliper with a PF "Z" pad will have 4.6mm more piston travel
than the factory Textar pad.
*  A Big Red Caliper with a PF Z pad will have 5.0mm more piston travel than
the aftermarket porterfield AP594-R4 ("the rotoreaters")
*  A Big Red Caliper with a PF Z pad on a 32mm rotor will have 2.6mm MORE
piston travel than a Big Red Caliper on a 30mm rotor with a stock Porsche
factory pad
*  A Big Red Caliper with a PF Z pad on a 32mm rotor will have 3.0mm MORE
piston travel than a Big Red Caliper on a 30mm rotor with Porterfield AP594-R4
*  All factory 993TT pads come with 1.50mm antisqueal backing plates, none of
the aftermarkets do.  These can be added to aftermarkets or stockers in
1.50mm increments

Summary:  The real risk associated with running Big Reds is higher running
aftermarket pads, NOT clamping a 30mm rotor.

HTH clear up the carnage the crows left

Scott Justusson
QSHIPQ Performance Tuning
"Old" Big reds on 44tq