FLOATING CALIPER.- The floating caliper type disc brake (fig. 7-17) is designed to move laterally on its mount. This movement allows the caliper to maintain a centered position with respect to the rotor. This design also permits the braking force to be applied equally to both sides of the rotor. The floating caliper usually is a one-piece solid construction and uses a single piston to develop the braking force.

Operation of a floating caliper is as follows:
Fluid under pressure enters the piston cavity and forces the piston outward. As this happens the brake pad contacts the rotor.

Figure 7-17.- Floating caliper.

Additional pressure then forces the caliper assembly to move in the opposite direction of the piston, thereby forcing the brake pad on the opposite side to contact the rotor.

As pressure is built up behind the piston, it forces the brake pads to tighten against the rotor. This action develops additional braking force.

SLIDING CALIPER TYPE.- The sliding caliper type disc brake (fig. 7-18) is mounted in a slot in the caliper adapter. It is a variation of the floating caliper, using a single piston and operating on the same principle, whereby the piston applies pressure to one brake pad and the movable caliper applies pressure to the other.

This design has two major sections- the sliding caliper and the caliper adapter (anchor plate). Each has two angular machined surfaces: this is where the sliding contacts come into play. The machined surfaces of the caliper housing slide on the mated

Figure 7-18.- Sliding caliper.

surfaces of the caliper adapter when the brakes are applied.

FIXED CALIPER.- The fixed caliper disc brake (fig. 7-19) is rigidly mounted to the spindle or splash shield. In this design, the caliper usually is made in two pieces and has two or more pistons in use.

The pistons accomplish the centering action of the fixed caliper, as they move in their bores. If the lining should wear unevenly on one side of the caliper, the piston would take up the excess clearance simply by moving further out of the bore.

As the brakes are applied, fluid pressure enters the caliper on one side and is routed to the other through an internal passage or by an external tube connected to the opposite half of the caliper. As pressure is increased, the pistons force the brake pads against the rotor evenly, therefore maintaining an equal amount of pressure on both sides of the rotor.