Front axle

[454_72_4X4]

Originally Posted by pumpkin

Its actually the other way around. the drum brakes have a residual check valve that keeps a small amount of preasure in the system to help keep the seals in the wheel cylinders sealed. with disc-drum the check valve is only for the drum brakes, and there is a delay valve for the disc brakes to allow the drums to catch up. I have used a drum brake master on a disc setup and had it work well. the biggest thing with a disc brake master is the size of the resevoir, cuase as the brakes where the fluid level goes down.

You're close pumkin.

Actaully there is a residual pressure valve in both disc and drum brake systems.
In a drum brake setup it's function is the keep the brake shoe springs from drawing the shoes away from the drum. It usually holds about 10lbs of pressure.
In a disc brake system it holds about 2 lbs of pressure.

The big question is "where is this residual pressure valve located on different systems"? I've been trying half heartedly for quite some time to come up with a definate answer to this.
Are they always in the master cylinder, or in the proportioning valve, or both, or...?