Hi, I have a question. I have manual brakes front disc and drum rear. What is the correct master cylinder bore size to use if I do not change anything other than that? will the car have a soft pedal using 7/8 in. bore or will it be so hard I would have to stand on the pedal to stop? What happens if I use the 1 in bore? thanks for any info miller.
Might depend on the rest of the braking system, and what car it's in, etc. We can only guess. Sometimes 1" is fine, sometimes 7/8" is fine, sometimes 1-1/4 is good, sometimes 3/4 is good.
Smaller bore = easier to push but pedal travel is longer. Larger bore= harder to push but shorter travel. Lots of things to consider ...pedal ratio, wheel cyl bore sizes, caliper bore sizes and fluid volume needs.
I called Wilwood and asked the same questions, they asked me what Calipers I was using, and the pedal ratio, and what kind of car it was going in. When that was all answered they recommended a 15/16 bore. Turns out my stock master cylinder and pedal had bad geometry. It was 4:1 which is a good ratio for power brakes. I needed it to be in the neighborhood of 6:1 for manual brakes. I fixed that, so it should be good now. They car still has the motor out so I haven't tried it yet.
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