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COMMON PROBLEMS WITH BRAKE DRUMS (continued)
Scored Drums
Scored drums are signified by circumferential grooves on the braking surface and
excessive lining wear. If the scoring is not deeper than the maximum rebore
diameter, the drum may be rebored and returned to service. The linings should be
replaced and the braking system should be checked to make sure excessive amounts
of abrasive material are not entering into the lining-drum contact area. If the scoring
is deeper than the maximum rebore diameter,
replace the drum immediately.
Out-Of-Round Drums
Variations in drum diameter at different points on the braking surface indicate
out-of-round drums. The drum should be machined within allowable rebore limits to
restore concentricity. Do not exceed the maximum rebore limit of turned drums, and
replace drums which are worn beyond their specified maximumdiameter. If you are
unable to restore concentricity by reboring the drum,
replace it with a new one.
It
may be necessary to replace drums in pairs to assure proper brake drum balance and
braking efficiency.
Excessive Wear and Galling
Excessive wear along the edges of the lining contact area, or in areas coinciding
with the rivet holes of the lining, is usually caused by abrasive material collecting
between the lining and the drum/rotor. Remove the abrasive material from the
system and check the drum for scoring. If the brake drum is scored beyond the
maximum limit,
replace the drum immediately.
Install dust shields to restrict the
amount of abrasive material which can enter the braking system.
Excessive wear can also be caused by misaligned brake shoes. If the shoes are not
“square” to the braking surface, uneven forces are applied. This can result in deep
grooves in the braking surface. If the brake drum is scored beyond the maximum
limit,
replace the drum immediately
. Correct the brake shoe alignment to alleviate
further grooving. Brake drum galling in an abnormal wear pattern is due to initial incompatibility between the brake drum lining and
the brake surface. This condition may correct itself due to brake drum and lining wear. If severe, consider replacing the lining and/or the
brake drum.