Brake Systems: Drums

NOTE: Determine the need to recondition based upon individual drum conditions that follow. Friction material replacement does not require drum reconditioning unless other justifications exist. Do not recondition new drums unless they are being pressed or bolted onto an existing hub. It is not necessary to replace drums in axle sets. However, when replacing or reconditioning a drum due to the conditions that follow, you may suggest reconditioning of the other drum on the same axle to eliminate uneven braking behavior. Always wash drums after servicing or before installing.

Condition	Code	Procedure
Balance weight missing Affecting performance	A	Require repair or replacement
Balance weight missing Not affecting performance		No service suggested or required
Bell-mouthed, affecting performance	A	Require reconditioning or replacement
Cooling fin broken		No service suggested or required
Cracked	B	Require replacement
Drum diameter is greater than OEM ""machine to"" specifications but less than ""discard at""	1	Suggest replacement
specifications, and the drum does not require reconditioning
NOTE: Only applies to vehicles for which OEM ""machine to"" specifications exist. If OEM does not supply ""machine to"" specifications, the drum may be worn to discard specifications
Drum diameter will exceed OEM ""machine to"" specifications after required reconditioning	B	Require replacement
NOTE: If OEM does not supply ""machine to"" specifications, you may machine to discard specifications.
Hard -spotted	2	Suggest reconditioning or replacement
Measured diameter is greater than OEM discard specifications	B	Require replacement
Out-of-round (runout), affecting performance	A	Require reconditioning or replacement
Out-of-round (runout), exceeding manufacturer's specifications	B	Require reconditioning or replacement
Scored	B	Require reconditioning or replacement
Surface threaded due to improper machining	B	Require reconditioning or replacement
Tapered, affecting performance	A	Require reconditioning or replacement