Master Cylinders

When selecting brake master cylinders, you'll notice with a smaller bore, you get more pressure but less volume. With a larger bore you get less pressure but more volume. You need to make sure that you have enough volume to supply your brake calipers, but at the same time, enough pressure.

For tandem master cylinder pedal assemblies, offroad trucks and buggies will have more bias to the rear brakes. 60% rear and 40% front is a common starting point, with a lot of offroad racing vehicles ending up at 30% front and 70% rear. Opposite of a street vehicle.

For single master cylinder pedal assemblies, here is an example of the math. Pushing the brake pedal with 100 pounds of force, a 6.25:1 pedal ratio and a single 3/4" bore master cylinder:

Pedal force at master cylinder:
100 lbs x 6.25 ratio = 625 lbs

3/4" master cylinder area:
A = π r²
A = 3.14159 x 0.375 x 0.375
A = 0.4418 in²

Brake line pressure:
625 lbs ÷ 0.4418 in² ≈ 1415 PSI out of a single brake master cylinder

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