Brake issue, Hydro boost and rear disc

[Schurkey]

That's backwards. Disc brakes have nine times the piston area, but that translates to 1/9th the force.

No. The master cylinder produces PSI, and some volume.

The psi has more surface area to act on, on disc caliper pistons than on drum pistons. 9 time the surface area, nine times the force on the friction material for a give brake system pressure.

 

[Erik the Awful]

Doh! That's right. I'm thinking of the master cylinder side, not caliper side.

Hell, I dunno, I just know that disc brakes have far less stopping force for the same brake pedal pressure. Their only upshot is they require less adjustment, and that's a very solid upshot.

 

[Schurkey]

They require lots of adjustment...but that adjustment is automatic via the piston sliding on the square-cut seal. If the piston seizes on the seal, braking power is affected.

Some calipers with a parking brake feature need to have the park brake operated for the piston to adjust properly. I've never actually dealt with those enough to figure out how they work.