Bendix Commercial Vehicle Systems ADB22X-V Air Disc Brakes - Manual (Page 3)

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1.3 Rotor Identifi cation
See Figure 4 to help you identify which type of rotor is used
on the axle being inspected. Note that the maintenance
inspection procedure will depend on the type of rotor
installed.
Conventional
Rotor
Bendix ® Splined
Disc ® Rotor
FIGURE 4 - ROTOR IDENTIFICATION
CAUTION: Rotors may not be mixed on a single axle:
axles are only permitted to have all conventional or all
splined disc rotors.
1.4 Wear Sensor Identifi cation
See Figure 5 for the electronic wear sensor that may be
present.
Sensor . . . . . . . . . . . . . . . . . . . . . 101
Cable to Electrical Supply. . . . . . . 103
Cable Protection Plate . . . . . . . . . 104
Cable Guide (two designs) . . . . . . 105
103
Cable to Electrical
Supply
104
Cable Protection
Plate
101
Sensor
101
Sensor
105
Cable Guide
(2 alternate
designs used)
Consult the instruction sheet included with wear
indicator kits for installation information.
FIGURE 5 - ELECTRONIC WEAR INDICATOR COMPONENTS
1.5 Operation
Bendix air disc brakes convert air pressure into braking
force. (See Figure 6.) When the vehicle brakes are
applied, air enters the service brake chamber through
the supply port, applying pressure within the diaphragm.
The pressure expands the diaphragm — applying force
to, and moving, the pressure plate and push rod forward.
The push rod acts against a cup in the internal lever which
pivots on an eccentric bearing moving the bridge. Moving
against a return spring, the bridge transfers the motion to
two threaded tubes and tappets, which move the inner
brake pad. The inner brake pad (from its normal position
of having a running clearance between it and the rotor)
moves into contact with the brake rotor. Further movement
of the bridge forces the caliper — sliding on two stationary
guide pins — away from the rotor. That, in turn, pulls the
outer brake pad into the rotor. The clamping action of the
brake pads on the rotor applies braking force to the wheel.
Supply Port
Return Spring
Push Rod
Lever
Outer Brake
Pad
Inner Brake Pad
Rotor
Eccentric Bearing
Service Brake
Chamber
Bridge
Pressure
Plate
Diaphragm
FIGURE 6 - CROSS-SECTION VIEW SHOWING BRAKE
OPERATION
1.5.1 Brake Release and Adjustment
When the vehicle brakes are released, the air pressure
in the service brake chamber is exhausted and the return
springs in the chamber and the bridge return the air disc
brake to a neutral, non-braked position. To maintain the
running clearance gap between the rotor and the brake
pads over time, the non-braked position is mechanically
adjusted by a mechanism in the caliper. The adjustment
mechanism operates automatically whenever the brakes
are activated, to compensate for rotor and brake pad wear
and to keep the running clearance constant. During pad
or rotor maintenance, the technician manually sets the
system’s initial non-braked position. The total running
clearance (the sum of clearances on both sides of the
rotor) should be between 0.024 to 0.043 in. (0.6 to 1.1 mm).