Quote:
Are you using square inches?
square inches = area
cubic inches = volume
My front calipers have two 28mm and two 32mm pistons per side. The total volume is less than you'd think.
The rears use 28mm and 30mm pistons. Again, fairly low volume.
The manual master has a 1-1/8" bore.
If you're getting that much pad movement then something is wrong. Brake pads normally ride a couple thousandths of an inch off the rotor. Anything more will lead to a squishy pedal.
I just didn't understand your formula for brake pad movement in the spreadsheet that is here:
http://3gduster.com/brakes.html
Instead, I calculated the volume displaced by the master cylinder:
((.9375/2)^2)*3.1416*.8333 = .5752 ci (MC displacement)
and then calculated the movement of a single piston with that volume with an area of 17.2 (4.3 sq in per caliper * 4 calipers).
.5752 / 17.2168 = .0334" of movement
Note: I then checked the math in excel, calculating the volume of a cylinder for four 44mm cylinders and four 40mm cylinders:
((44/25.4/2)^2)*3.14*.0334 = .0787
((40/25.4/2)^2)*3.14*.0334 = .0651
BTW- your total piston area in the front is ~4.4 sq in.
**I'm not arguing the brake pads actually move this much. All of this is just an exercise in determining when you have too small of a master cylinder.
Last edited by uhcoog1; 02/14/13 05:05 PM.
