The disc brake assembly consists of a brake caliper,
brake rotor assembly, disc brake pad assembly, brake caliper mounting plate,
and brake shield. The brake rotor assembly is bolted to the wheel hub and
turns with the wheel. The brake caliper housing has machined bores and pistons.
A seal in a groove of the wall in each bore provides a hydraulic seal
and retracts the piston when fluid pressure is relieved. A dust boot keeps
the piston bore clean. A metal heat shield protects the dust boot from the
heat caused by braking friction. The brake caliper is mounted by a brake
caliper retainer and brake caliper retainer spring to the stationary brake
caliper mounting plate. The brake caliper mounting plate and brake shield
are bolted to the axle flange (rear) or steering knuckle (front).
The brake pad assemblies are held in place on each side of the brake
rotor. The outer brake pad moves with the brake caliper housing. The inner
brake pad is held in place by the brake caliper mounting plate. All of the
original equipment brake pad linings are free of asbestos.
Applying the brake pedal causes hydraulic pressure to move the brake
caliper pistons. This causes the brake pads to clamp the brake rotor. The
brake caliper adjusts the clamping position by sliding laterally in the
support rails on the brake caliper mounting plate.
Releasing the brake pedal relieves the pressure applied to the brake
caliper pistons. The pistons are pulled back in the bore by the action of
the square cut piston seals running to the original shape. This allows
for a running clearance between the brake pad linings and brake rotor.
Servicing Information
| • | Replace all components included in the repair kits used to service
the brake caliper. |
| • | Lubricate rubber parts with clean brake fluid in order to ease
assembly. |
| • | Do not use lubricated compressed air on brake parts because rubber
component damage may result. |
| • | Flush the hydraulic brake system with clean brake fluid when you
install new parts. |
| • | After a hydraulic component has been removed or disconnected,
if necessary, bleed all or part of the brake system. Refer to
Hydraulic Brake System Bleeding
in Hydraulic Brakes. |
| • | Replace disc brake pads in axle sets only. |
| • | The torques specified are for dry, unlubricated fasteners. |
| • | Perform service operations on a clean bench, free from mineral
oil and any other contaminants. |
| | Important: Before moving the vehicle, pump the brake pedal several times to make
sure the pedal is firm. Do not move the vehicle until a firm brake pedal has
been obtained.
|
| • | Check the brake fluid level in the master cylinder after pumping the
brakes. |
Brake Rotor (JF9)
The rotor and hub are separate components that are bolted together.
During operation, the brake rotor turns between the brake linings and basically
free-wheels until hydraulic pressure, created by applying the brake pedal,
is converted by the brake caliper to a stopping force. This force acts equally
against the pistons and the bottom of the brake caliper bore to move the
pistons outward and move (slide) the brake caliper inward, resulting in
a clamping action on the front brake rotor. This clamping action forces
the brake pad linings against the brake rotor, creating friction to stop
the vehicle. The vented area between the rotor braking surfaces allows for
efficient heat dissipation.
Brake Caliper (JF9)
The brake caliper is a rail slider type with dual-pistons. A seal in
a groove of the wall in each machined bore provides a hydraulic seal and retracts
the piston when fluid pressure is relieved. A dust boot keeps the piston
bore clean. A metal heat shield protects the boot from the heat caused by
braking friction.The brake caliper mounts using a brake caliper retainer,
brake caliper retainer spring, and a brake caliper retainer bolt to the
brake caliper mounting plate.
