
HYDRAULIC BRAKE SYSTEMS 423
Figure 25.28 Disc pad neglect in service (Ferodo)
Heat spotting Either the lining is not sufficiently con-
formable to the drum, or the latter is distorted so that
lining contact occurs only at small heavily loaded areas.
Discoloured regions and sometimes cracks appear on
the friction track of the drum, this being accompanied
by heavy gouging of the lining.
Fading Where this has occurred the lining material
degrades or flows at the rubbing surface (an explanation
of heat fade has been given earlier). Surface cracks on
the brake drum friction track again may be associated
with such arduous usage, their presence or