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BRAKE DRUM AND ROTOR SERVICE INFORMATION
SERVICE INFORMATION
To achieve maximum drum life and optimum performance, proper brake maintenance and brake balance are
essential. Consult your truck or trailer manufacturer’s maintenance manual for proper maintenance of the
braking mechanism.
The following procedures are suggested as a means of obtaining maximum service and to determine the
need for replacement.
NOTICE: When replacing lining, brake drum or rotor on one end of the axle, replace the same
components on the other end of the axle. This will maintain proper braking load on the axle.
A1. Inspection of Brake Drums or Rotors
When relining brakes, the brake drum or rotor should be cleaned and inspected. To be
suitable for further service, the brake drum or rotor 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 or minimum thickness cast or stamped on the rotor.
C.
The mounting holes and pilot must be round and true.
D.
The mounting surface must be clean and flat.
CAUTION: If any of the above conditions are not met, the brake drum or rotor should be replaced.
A2.
Turning the Brake Surface
It may be desirable to turn or resurface the braking surface to remove small heat checks or
other surface defects. The following should be noted when turning:
A.
When resurfacing a drum, allow at least 0.040 under the maximum diameter and
on a rotor 0.040 over the minimum thickness for additional wear. For example,
this usually means the drum may be turned a total of 0.080 over the brake surface
diameter of a new brake drum.
Example: New Drum Diameter
16.500
Rebore Allowance
0.080
Diameter after
rebore limit is
reached
16.580
Wear Allowance
0.040
Maximum Diameter
16.620
WARNING: DO NOT TURN OR WEAR A BRAKE DRUM OR ROTOR BEYOND THE MAXIMUM
DIAMETER OR MINIMUM THICKNESS STAMPED OR CAST ON THE BRAKE DRUM OR ROTOR.
The maximum diameter or discard diameter is the maximum diameter to which the brake drum may be
turned or worn, and still be usable. If any portion of the brake surface exceeds the maximum diameter it
must be discarded. The maximum diameter cast into the back plate portions of the brake drum supersedes
all published information.