Meritor TM Series Service Manual page 19

3 Inspection & Maintenance
Heat Crazing (Fig 3.5 & Fig 3.6)
Heat crazing is fine cracks on the rotor's surface. This is a normal
condition that results from continuous heating and cooling of the
friction surface. Braking under normal operating conditions can
cause cracks to separate and deepen, increasing lining wear.
There are two types of heat crazing: light and heavy.
Light Heat Crazing (Fig 3.5)
Light heat crazing is fine, tight cracks in the rotor's surface.
Continue to use a rotor with light heat crazing.
Fig. 3.5
Heavy Heat Crazing (Fig 3.6)
Heavy heat crazing is cracks in the rotor's surface that extend
radialy and have an individual length of up to 75%brake path
width. Refinish or replace a rotor that has heavy heat crazing.
Maximum length = 75% of "A"
Fig. 3.6
Meritor HVS TM Series Axle
19
NOTE
: Surface finish after machining should be 5 microns
maximum.
NOTE
: Localised crazing / blue patches / cracking in only one
part of the rotor could be caused by rotor run-out or thickness
variation. Refer to vehicle manufacturer for tolerances.
Scoring (Fig 3.7)
Scoring is deep circumferential grooves that can occur on both
sides of the rotor's surface. If the groove or multiple scores are of
a depth less than 0.5 mm, continue to use the rotor. If the groove
/ scores are greater than 0.5 mm, refinishing the rotor is
recommended.
Refinishing the rotor is recommended before fitting new brake
pads.
Fig. 3.7
A