Hugh,
I use a 3/4" for the fronts and 5/8" for the rears with a 10# residual
pressure valve on my spitfire with 16P calipers on the front and the .700 rear
wheel cylinders. I don't know that I like the small m/c on the rear as I
can't get as much rear brake as I'd like. The 3/4 on the front is nice, the
pedal effort is high, but modulation is quite good as Bill describes. I don't
have a brake fade or need to pump the brakes up at all without a residual
pressure valve on the fronts. I use a tilton pedal setup and I like the
balance bar. I have it setup with the adjusting cable to play with, but I
have yet to perform any adjustments while on track.
One thing to remember with a proportioning valve is that you are only reducing
pressure to the line which it is on from the max pressure (no valve) and you
are NOT increasing pressure to the other part of the system. So if the valve
is on the rear you will only decrease pressure from full, but you can never
add more pressure. So m/c size becomes more important. The balance bar
actually transfers leverage from the pedal to decrease pressure on one system
and increase the other.
Aaron Johnson
#38 F-Prod Spit MkIV Oregon Region SCCA
http://www.geocities.com/spitracer9
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