4. MAINTENANCE
4.7 AS REQUIRED SERVICE
1. Remove the wheels and drums.
2. Inspect the brake cam rollers, anchor pins, camshaft support bushings and cam shaft
for wear. Replace components as necessary. Refer to axle manufacturers service manual for
proper procedures.
3. Inspect brake linings for wear, loose rivets and any signs of grease on the braking sur-
face. Always replace brake linings which become contaminated with oil or grease. Ensure
sufficient lining remains to keep rivet heads away from drum surface. Check retainer and
return springs for breakage or distortion.
4. Check the brake drums. To be suitable for further service the brake drum should pass
the following checks;
a. The brake surface should be free of scoring, excessive heat checks and free of cracks.
b. The brake surface diameter should be within the maximum diameter cast or stamped
on the drum.
c. The mounting holes and pilot must be round and true.
d. The mounting surface must be clean and flat.
5. Service the wheel bearings and seals if required. See section 4.8C for wheel bearing
and seal maintenance.
4.7E Anti-Lock Brakes (ABS)
This machine is equipped with an anti-lock brake system, as required by FMVSS 121, effec-
tive March 1, 1998. Please refer to your local dealer for maintenance.
Proper Operation: If the ABS indicator lamp comes on and stays on when you apply the
brakes to a moving vehicle, the trailer ABS is not working properly. The ABS must be ser-
viced as soon as possible upon completion of your trip to ensure full anti-lock braking capa-
bility. See your authorized dealer for ABS braking service.
4.7F Automatic Slack Adjusters
This machine is equipped with automatic slack adjusters as required by FMVSS 121, effec-
tive October 20, 1994. Manual adjustment of the automatic slack adjuster should be done
only after lubricating, overhaul on brakes, or replacing slack adjuster.
To determine proper slack adjuster performance the following inspection should be made:
• Check the amount of push rod travel. Maximum should not exceed 2" for Type 30
chambers.
• Check the angle between the slack adjuster and push rod. With the brakes applied, the
angle should be 90° (+/- 5°).
• With air pressure applied to brakes, check the lining to drum contact. The contact should
approach 100%. Use a .010" feeler gauge if in doubt. It should not fit between the lining and
drum during brake application.
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