DISC BRAKE ASSEMBLY
1.Head assembly. 2. Anchor pin. 3. Friction pad. 4.
Metal backing. 5. Piston. 6. Disc.
HEAD ASSEMBLY (CAUPER)
1. Anchor retaining bolt. 2. Metal backing. 3. Friction
pad. 4. Anchor pin. 5. Bleed valves. 6. Piston and -
al. 7. Head assembly.
Oil flow to the brakes is through lines and drilled
passages to all pistons within each head assembly.
When an application of the brakes is made, the
hydraulic pressure is made the same (balances) the
pistons and the force on each side of the disc is the
same. The pistons do not have return springs.
To make a pad replacement the caliper need not be
removed. For replacement of pads, remove the anchor
pin and slide the pad out.
CAUTION: Do not make a brake application with pads
removed. The pistons must not be permitted to extend
out of their bores as the pads are removed. Open the
bleed valves on the caliper to release any pressure on
the piston. If the pistons extend and let the seals come
out, caliper removal will be needed to install the pistons.
Two bleed valves on each caliper are used to let air out
of the hydraulic brake system. Let air out of the brakes
(bleed) whenever a line is disconnected in the hydraulic
The parking brake will not let the output shaft of the
transmission turn when the air pressure to the brake
chamber is below 40 + 5 psi (280 + 35 kPa). The brake
drum with shoes inside is on the output shaft of the
The brake chamber activates the shoes. The
parking brake is activated by a spring and released by
air pressure. Force of the spring moves the rod of the
brake chamber and the brake lever is pulled UP by the
rod to activate the brake. Air pressure works on the
diaphragm to cause compression of the spring and
extension of the rod. The rod pushes the brake lever
DOWN to RELEASE the brake.
Control Valve for Parking Brake
The control valve, which is on the dash, has control
over the supply of air that goes to the chamber of the
parking brake. With valve knob (1) pulled OUT, the line
to the brake chamber is open to the atmosphere and
causes the application of the brake. With valve knob (1)
pushed IN, air goes from the reservoir into the chamber
of the parking brake and releases the brake.
FLOW OF AIR; APPUCATION OF PARKING BRAKE
1. Knob and pin assembly. 2. Valve body. 3. Spring. 4.
Orifice. 5. Outlet (to chamber of the parking brake). 6.
Inlet (from air reservoir). 7. Exhaust (to atmosphere). 8.