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Brake Drum Failure Analysis
Martensite is formed by
rapidly heated brakes to
approximately the 1400°
F range followed by rapid
cooling. This condition is
caused by brake drag or
torque imbalance.
Replace brake drum.
Check for dragging
brake, check balance
between tractor/trailer
and wheel to wheel (i.e.
air distribution, brake ad-
justment, and power A/L
factors.)
The brake surface shows black spots which
are slightly raised and are hard and brittle
Martensite Spots
Leaking oil/grease seal
or improper lubrication of
brake components.
Repair source of oil or
grease leak, clean the
brake drums and replace
the linings.
The drum shows discolored spots on sur-
face, with oil or grease on brake assembly
Grease Stained Drums
Grooves, loose rivets or
bolts, or foreign material
in rivet holes. Abrasive
material in brake drum.
Poor quality brake lining.
Repair or install rivet
plugs.
Dust shield may cause or
cure this problem.
Consult lining manufac-
ture.
Turn brake drum if within
limits or replace.
The problem is indicated by a grooved ap-
pearance on the brake surface
Scored Drums
Problem
Probable Causes Recommended
Actions
TMC RP 608A © 2003 – TMC/ATA – Reprinted with Permission