Troubleshooting guide

62
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
Foundation Brakes
Braking torque is established by the vehicle
manufacturer and is determined by the designed
axle weight. Brake size (diameter), brake block or
pad characteristics, and the foundation brake design
(S-Cam, air disc, etc.) infl uence brake torque. In the
case of S-Cam brakes, the torque is carefully evaluated
in relation to drum capacity, drum area, and lining area.
For air disc brakes, the torque is evaluated in relation to
rotor/pad specifi cations. We recommend that you consult
the vehicle manufacturer before attempting any changes
that would affect brake torque.
Mechanical friction within the foundation brake can
affect brake output torque. The components of the
foundation brake are subject to high forces and should
be periodically checked and lubricated as necessary.
Friction materials (e.g., brake block and lining
segments, etc.) affect vehicle stopping performance
and are a factor in wear balance from front to rear.
Replacement material should be chosen for its stopping
performance, as well as wear characteristics. At
minimum, always replace friction material on both ends
of an axle whenever one side is being serviced. For rear
axles, it is recommended that friction material on all axles
be replaced at one time.
With air disc brakes, the rotor-friction couple
is carefully designed and validated for optimal
performance. When replacing air disc brake pads,
always select replacement pads that have been validated
to perform with the rotor used, in order to prevent
premature or uneven pad wear or damage to critical
disc brake components (e.g., cracked rotors), which can
adversely affect braking performance.
Brake Adjustment
One of the most important factors in obtaining maximum
mechanical output of the chamber is proper brake
adjustment. All chamber strokes should be adjusted
to approximately the same stroke, and the adjustment
should be made so that the chamber stroke is as short as
possible without the brakes dragging. Improperly adjusted
brakes waste air, reduce leverage, and contribute to poor
brake performance. In many cases, complaints of poor
or insuffi cient braking power can be remedied by proper
brake adjustment.
Brake System Maintenance
Because no two vehicles operate under identical
conditions, maintenance and maintenance intervals
will vary. Experience is a valuable guide in determining
the best maintenance interval for any one particular
vehicle.
In Section 9, Air Brake System Troubleshooting, you will
fi nd some suggested tests for determining the overall
condition of the air brake system and to help quickly
locate problem areas. The tests check both leakage and
device function. Performing these tests on a quarterly
basis and recording the results of the tests in the vehicle
maintenance records would provide a valuable basis for
performance comparisons/trends and assist in deciding
maintenance intervals.
Air Brake System Balance: Mechanical Systems