The front disc brake system consists of the following components:
| • | A rotor mounted to a wheel hub/bearing assembly |
| • | A caliper assembly consisting of a caliper housing, caliper mounting
bracket, brake pads, clips, slide pin bolts , and support bushings mounted
to the steering knuckle |
| • | The rear disc brake system consists of the following components: |
| • | A rotor mounted to an axle shaft flange or a rear wheel hub |
| • | A caliper assembly consisting of a caliper housing, caliper mounting
bracket, brake pads, clips, slide pin bolts , and support bushings mounted
to a backing plate |
The caliper mounts in a way that allows the caliper to move laterally
inboard as the brake pads wear. The caliper housing is a 1 piece casting with
the inboard side containing the piston bore. A square cut rubber seal
fits in a groove in the piston bore in order to provide a hydraulic seal
between the piston and the caliper bore. The piston seal also acts as
a return mechanism for the piston.
Applying the brake pedal causes the hydraulic pressure that moves
the caliper piston. The piston then forces the inboard brake pad against the
inboard braking surface of the rotor. Increasing the force against the
rotor causes the caliper to move inboard. The outer brake pad then contacts
the outboard braking surface of the rotor. The force of the 2 brake pads
being squeezed against the rotor provides the desired braking forces
to be generated.
Releasing the brake pedal relieves the pressure applied on the piston.
The square cut seal on the piston relaxes and pulls the caliper piston back
into the bore slightly. This allows a running clearance between the
brake pads and the rotor braking surfaces.
Servicing Information
| • | Replace all components included in the repair kits. |
| • | Lubricate the parts as specified. |
| • | Do not use lubricated shop air on the brake parts. Shop air can
damage the rubber components. |
| • | If necessary, bleed all or part of the brake system after you
remove or disconnect any hydraulic component. |
| • | Replace the brake linings in axle sets only. |
| • | The torques specified are for dry, unlubricated fasteners. |
| • | Perform service operations on a clean bench. Verify that the bench
is free from mineral oil and other contaminants. |
| • | Use extreme care when doing any work around antilock components
in order to prevent damage or misalignment. |
| • | Pump the brake pedal several times in order to ensure the brake
pedal is firm prior to moving the vehicle. Do not move the vehicle until you
obtain a firm pedal. Inspect the brake fluid level in the master cylinder
after pumping the brakes. |
Rotor
The front disc brakes use 2 of four different styles of rotors. The
RWD 15 series and the 4WD 15 series models use outboard mounted 29 mm
wide ventilated rotors. The RWD 25 series and the 4WD 25 series models
use outboard mounted 38 mm wide ventilated rotors.
The rear disc brakes use one of 3 different styles of rotors. The RWD
15 series and the 4WD 15 series models use outboard mounted 20 mm
wide ventilated rotors. The RWD 25 series and the 4WD 25 series models
use 2 different outboard mounted 29 mm wide ventilated rotors
depending on whether the vehicle is equipped with 9.5 in rear axle
or a 10.5 in rear axle. The rear rotor also functions as the drum
for the parking brake.
Caliper
The front disc brakes use 2 different types of calipers. The 15 series
models have cast iron housings equipped with 51 mm dual bores. The
25 series models have cast iron housings equipped with 57 mm
dual bores.
The rear disc brakes use 3 different types of calipers. The 15 series
pickup models have aluminum housings equipped with 54 mm single bores.
The 15 series utility models have aluminum housings equipped with
45 mm dual bores. The 25 series models have cast iron housings
equipped with 51 mm dual bores.
