19
5
a
A
1
B
1
D
1
C
1
» Pneumatic Disc Brake SL7 - SM7
FUNCTIONAL AND VISUAL CHECK
5.1.7 - Tolerances and examples of cracks and grooves
on a brake disc.
If these recommendations are ignored, there is a risk
of an accident. If the brake pads and/or the brake disc
are worn down excessively, brake performance will be
reduced and may be lost completely.
Grinding of a Knorr-Bremse Splined Disc
®
is not
allowed.
max. 0.75 x a
max. 1.5 mm
5.1.7 Check the discs per axle at each change of pads for
grooves and cracks. If necessary replace the disc.
The figure shows possible surface conditions of the brake
disc.
A1
= Small cracks spread over the surface are allowed
B1
= Cracks less than
1.5 mm
deep or wide, running
in a radial direction are allowed
Cracks to a max. length of 0.75 x’
a
’ are allowed
(
a
= width of the friction ring)
C1
= Unevenness of the disc surface less than
1.5 mm
deep is allowed
D1
= Cracks going through to the cooling duct or onto
the inner or to the outer edge of the friction ring are
not allowed and the disc MUST BE REPLACED.
The photograph shows a real-life example of such cracks and
wear grooves.
Note:
In case of surface conditions
A1
,
B1
or
C1
, the disc can
continue to be used until the minimum thickness
A = 37 mm
is reached.
Knorr-Bremse discs are normally service-free and grinding
when changing pads is not necessary. However, grinding
could be useful, e.g. to increase the load-bearing surface of
the pads after severe grooving on the entire friction surface
has occurred. To meet safety requirements, the minimum
thickness after machining must be greater than
39 mm.
In addition, the recommendations of the vehicle
manufacturer about the machining of the brake disc MUST
be followed.
C1
D1
B1