IMPORTANT: Before caging the parking brakes,
make the connection to a towing vehicle or
chock the tires.
After correcting the brake system problem, uncage
the parking brakes before resuming normal vehicle
operation.
Bosch Hydraulic Pin Slide
Brakes
General Information
The Bosch hydraulic pin slide disc brake is a two-
piston sliding caliper brake and is used at both the
front and rear wheel locations. Each pin slide caliper
disc brake wheel installation is made up of a caliper
assembly, anchor plate assembly, and disc brake
pads.
Caliper Assembly
The caliper assembly has two hydraulic piston bores.
The piston bores contain pistons, piston seals, and
piston boots. The caliper assembly attaches and
slides on sealed pins located in the anchor plate.
The caliper housing is the main component of the
caliper assembly. The material of the caliper housing
is ductile iron and has a protective coating to provide
additional environmental protection. The disc brake
caliper housing straddles the rotor, the inner pad,
and the outer pad.
Anchor Plate Assembly
The anchor plate assembly includes lubricated float-
ing guide pins sealed by rubber boots. The anchor
plate abutments are protected by stainless steel slip-
pers.
Disc Brake Pads
There are two pads per caliper assembly, and they
are the inner and outer pads. The inner pad is lo-
cated between the caliper piston and rotor. The outer
pad is located between the rotor and caliper housing
legs. The pads are made of friction material and a
stamped steel backing plate. The pads are referred
to as the shoe and lining assembly. These brake
pads can be removed without removing the caliper.
Operation
Before driving the vehicle, secure all loose items in
the vehicle so that they will not fly forward during a
full brake application. Check that the brake system
warning light is off after releasing the hand brake. If
the warning light does not go off, correct the problem
before continuing operation of the vehicle.
During normal braking stops, depress the foot brake
control pedal until braking action slows down the ve-
hicle. Increase or decrease the pressure on the
pedal so that the vehicle comes to a smooth, safe
stop. Apply the hand parking brake if the vehicle is to
be parked.
IMPORTANT: Make sure that the brake fluid in
the master cylinder reservoirs is up to the level
of the ridge that surrounds the reservoir. See
Fig. 13.2. Use only DOT 3 or 4 brake fluid in
the Bosch hyrdraulic pin slide brake system.
Meritor Cam-Master® Q Plus
Brakes
Cam-Master brakes are air-actuated, cam-operated,
foundation brakes. The Q Plus increases service life
and mileage between relines by providing more lining
thickness. A specially designed S-cam and heavy-
duty shoe return spring allow additional shoe travel
required to fully wear the thicker lining blocks. An
improved camshaft bushing contributes to longer ser-
vice life.
Cam-Master Q Plus Operation
When the brake pedal is depressed, compressed air
enters the brake chamber, causing the diaphragm to
move a pushrod assembly.
The pushrod turns the slack adjuster and brake cam-
shaft. As the camshaft turns, the S-type cam head
forces the brake shoes against the brake drum and
braking occurs.
When the brakes are released and air is exhausted
from the brake chamber, the actuator return spring
(within the brake chamber) and the brake shoe return
spring return the camshaft, brake shoes, slack ad-
juster, and pushrod to their released positions.
Hydraulic and Air Brake Systems
13.3
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