(updated: Nov 2007) Swept area of cylinder Brakes Disk 2.125 pistons X 4 = 14.16 sq in. move the pads 1/16" .0625 requires ----------- .885 cu in of fluid ------------------------------------------------------------------------ rear drums with 13/16" wheel cylinders X 2 pistons = 1.036 sq in .885 move the shoes, 1/16" .0625 requires .0064 ------------ ------------------- .0064 cu in fluid .891 total --------------------------------------------------------------------------- rear drums with 3/4" wheel cylinders X 2 .883 sq in .885 move the shoes, 1/16" .0625 .0055 ---------- -------------- .0055 Cu in fluid .8905 total --------- Brake line pressure Both the standard and power brake pedal, will actuate the 1" bore master to 1.4", however the brake line pressure will be greatly different and much lower with the power brake pedal. The ratio on a standard brake pedal is around 7:1, whereas the ratio on a power brake pedal is 4:1 ---------------------------------------------------------------------------------- The math says that a 1.4" throw will yield 1.099 cu in of fluid With correctly adjusted brakes: With a standard brake pedal (11.5" @ 7:1 ratio) on a disk brake car, with the correct actuator rod adjustment to the master cylinder piston, discounting any lost motion from worn parts, the pedal should drop 75-80% of it's travel, on the first stroke. This will take up any looseness in the system while applying the brakes. A second stroke will be shorter due to the proximity of the friction surfaces to the rotating mass. A standard drum brake system (no hydrovac) pedal will not drop very far, due to the small amount of fluid required to engage the brakes. The pedal drop will increase as friction surfaces wear and no brake adjustment is made.