Brake Math

-it's all about the square inch area of the master cylinder pushing against the square inch area of the caliper piston.

-Then you have a ratio between the pedal to the pivot length, and from the pivot to master cylinder rod length.

-If you had a 2" diameter piston in one caliper you have 3.1416 square inches of area.
-If you have a master cylinder that is 1" diameter you have .7854 square inches of area.
-So you take 3.1416, divide by .7854 and you get a hydraulic ratio of 4:1.

-This means that if you could get a pressure at the master cylinder rod of 180 pounds you get 180 times 4 or 720 pounds of force at the caliper piston.

-You can get the 180 pounds at the master cylinder pushrod by having a 9" long brake pedal arm hanging down, with the top end mounted say about 3" above the master cylinder piston, a pivot for the master cylinder rod clevis at 3" from the top, and then 6 inches from that pivot down to a foot pedal.

-the 6" divided by the 3" is a 2:1 ratio meaning that if you moved the foot pedal two inches you'd push the master cylinder rod 1".

-So to get 180 pounds at the master cylinder rod you'd need to push 90 pounds of push from your foot on the brake pedal.