All hydraulic foundation brakes are disc brakes. The Bendix type is used on the P72 chassis. The Dayton-Walther type is used on the P92 chassis.

The disc brake assembly consists of a caliper assembly, the rotor, the linings, and the anchor plate. Applying the brake pedal causes the hydraulic pressure to move the caliper piston. The piston then forces the inboard brake lining against the inboard braking surface of the rotor. Increasing the force against the rotor causes the caliper assembly to move inboard. The outer brake lining then contacts the outboard braking surface of the rotor. The force of the two brake linings provides the desired clamping action on the rotor.

Releasing the brake pedal relieves the pressure applied to the piston. The square cut seal on the piston returns to its normal position and allows a running clearance between the brake linings and the rotor.