[robnolimit]

On to Master Cylinders It's all about line pressure. And that means numbers. The first thing we all have to agree on is how hard to push on the pedal. The DOT standard is 30 to 40 lbs foot pressure. But we need a standard that everyone can agree on. I like to use 30 lbs on street drivers, and 40 lbs on race/performance builds. If thats OK with everybody, we'll start there. So, for the street, lets say 30 lbs of pressure comes from your foot. This would be multiplied by the pedal ratio. ?? What? I'll work on a picture for this. But for now, lets say you truck has a pedal ratio of 7-to-1. So, 30 lbs from your foot, times 7 from the pedal, = 210 lbs of force pushing into the master cylinder. Now to covert that into P.S.I. (line pressure) we need to know the size of the master cylinder. The area of the piston in the master can be calculated using the formula for the area of a circle. or, Area = 3.14 x R x R ( thats the best way I can type it in.) R being the Radius, or, 1/2 of the diameter. So, a 1" bore master has a 1/2", or .5" radius. 3.14 x .5 x .5 = .785 sq.in. of surface area. To get line pressure, we take the input force (lbs) and divide by the piston area (sq.in.) For our example, 210lbs / .785sq.in. = 267 lbs of line pressure. Not much. This will not stop your truck very well. So, what to do.