Document B862dL2M9GaZN4ejyarE86nvX

NAPA AUTOMOTIVE CAREER TRAINING Disc Brakes--Continued Caliper Assembly The caliper assembly is a non-rotating cast body which straddles the brake rotor. In each caliper assembly, brake pads are positioned on each side of the rotor. When the brakes are applied, the pads are forced into contact with the rotor, stopping the vehicle. Hydraulic pressure in the system is trans mitted to the brake pads through one or more hydraulic pistons which are part of the caliper assembly. Pistons, rubber seals and boots, and such hardware as guide pins, stabilizers, spring clips and bolts comprise the complete caliper assembly. Early caliper designs have been of a split housing, four piston fixed type. In this unit, a pair of pistons on each side presses against the brake pads on each face of the rotor. The caliper body is bolted directly to the steering knuckle of the car. In 1968, many automobile manufacturers changed to a single piston design caliper. In this unit, the caliper unit is one piece, having a slide-mounting to an anchor plate which is bolted to the steering knuckle. In each caliper you will also find piston seals. Some are located in grooves machined in each cylinder bore, others are located in grooves machined into the pistons. These seals provide a hydraidic seal between the piston and the cylinder wall. When hydraulic pressure builds up behind the single piston, located in the inboard side of the caliper, the inner brake pad is forced against the rotor. Simultane ously, the caliper housing slides on the anchor plate, forcing the outer brake pad against the rotor. 16 A dust boot protects the piston and cylinder walls from contamination. On some cars the boot is held in place by a retainer ring on the caliper face, and on others, a groove in the cylinder bore is used to hold the lip of the boot.