John Cunningham
I'm Awesome
Yeah, I did.
A 2-13/32 dia piston has 4.547 sq in area,, times 10psi=45.47 lbs of force, then divide that by 2, the pressure is only on one pad, but the caliper slides to equalize the pressure between the both of them.
That 10lb residual is holding 10lbs in each rear caliper, so each one of the 4 pads is pressing on its rotor side with ~22.235 lbs of force.
Ideally you want very little residual on discs, they have no retractor springs, the only retracting force is a tiny bit of "spring-back" in the rubber boot, they always drag a little, and the column height of the fluid above the calipers is plenty of pressure to keep the pads in light contact.
With discs the difference between "relaxed" and "hard braking" is only a few thousands of an inch.
I tend to agree with you that I am getting 10 psi to the rear either thru the master or abs. I am not sure how to know without taking the master cyl off and seeing if it has a residual pressure valve in it. I could take it our or just purchase an 01 to 07 Master Cyl that had 4 wheel discs...
Here is something another guy brought up...not sure how true this is but the master cyl on a 4 wheel disc set up require more brake fluid than a drum system and he claims that is another reason to change out the master cyl....they have different fluid capacitys which becomes important in a 4 wheel disc system. Funny thing is a dont feel any drag nor to the rotors look like that have been abused from draging...I am going to jack it up and run it and watch because if the caliper has that kind of residual pressure you would surly see it coming to a stop pretty fast after free wheeling...throw it in neutral and hit the brakes and the let off of them and see if the tire freely spins..or is draging...kinda crude but maybe a way to check for drag.