Some info on GTV6 Track Brakes

[Gerry Lehmann <lehmann@domain.elided>]

This discussion of transaxle car brake cooling
has scratched an old nerve.  I've spent way =

too much time bleeding GTV6 brakes trackside.
My GTV6 has had a long history of track time =

from the day it was new right up to the current.
As my wife and I both drive it,  (yes, she has
more trophies than me, but somebody's gotta
set the car up.), often in consecutive run
groups at time trials, we've had no problem
using up the brakes.  Particularly after =

they've heat soaked between sessions while we
swap drivers.  We tried most of the usual =

stuff, braided lines, hi temp fluid, amatuer =

brake ducting, all kinds of high performance =

pads, removed front shields  and drilled =

front rotors..... all of this with with some,
but not significant improvement.

Some years ago, having gotten frustrated with =

constantly boiling brake fluid problems at =

certain west  coast tracks, (Laguna Seca and =

the Streets of Willow),  I took an on board =

data logger to Laguna Seca for the weekend =

and recorded minute by minute data from =

thermocouples attached to all four calipers.

The short story for a GTV6.....Its all in the
rear!
- - The rear calipers generally ran 60 to 100F =

degrees hotter than the fronts after a few =

warmup laps.
- - The left (exhaust) side caliper ran another =

50 to 80 degrees warmer than the right side.
- - After 10 or 15 minutes the fronts would =

stabilize in the low to mid 300's, cooling =

down the straights and rising after the brake =

zones.......but the rears, although they also =

cycled on each lap, never cooled as much as =

they heated and thus overall kept rising a bit =

each lap until the left rear hit the 500s and =

the pedal went to the floor. =


The solution. Based on the above, I wrapped =

the rear exhaust with header wrap, slotted =

the rear rotors and installed a proportioning =

valve to move a bit of the braking chores =

frontwards.  (The latter is the right thing =

to do with sticky tires anyway, because with =

the extra adhesion of track tires you also =

have more weight transfer than the stock car =

was ever designed for and will tend to lock =

the rears early.)  The result.....I've had =

no brake problems since.

FWIW I'm going to write a bit more on this =

subject , particularly the proportioning valve, =

for the next issue of Craig Walker's GTV6 =

Newsletter.  If anyone not on his list is =

interested, drop me a note,  and I'll send you =

what I put together when I get it done.

Gerry Lehmann
lehmann@domain.elided
'85 GTV6 2.5 - with relatively trackworthy brakes
'86 GTV6 3.0 - Finally running!

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End of alfa-digest V7 #566
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