5020-M Owner's Manual
Kobelt Manufacturing Co. Ltd.
rev B
mnl5020-M.docx
11 of 27
The disc mounting bolts used must be of a suitable size and grade to safely resist the brake
torque plus the stresses induced from thermal expansion of the disc. For high temperature
disc applications, the holes for the mounting bolts must be machined oversized to allow the
disc to expand during operation. Ensure that adequate washers are used to bridge the gap
between the bolt and bolt hole.
Table 2: Mounting Bolt Radial Clearance
MOUNTING BOLT RADIAL CLEARANCE
Disc Bolt Circle
In [mm]
Maximum Disc Temperature, °F [°C]
400 [204]
500 [260]
600 [316]
700 [371]
10 [254]
0.011 [0.3]
0.014 [0.4]
0.017 [0.4]
0.021 [0.5]
15 [381]
0.016 [0.4]
0.021 [0.5]
0.026 [0.7]
0.031 [0.8]
20 [508]
0.022 [0.6]
0.028 [0.7]
0.035 [0.9]
0.041 [1.0]
25 [635]
0.027 [0.7]
0.035 [0.9]
0.043 [1.1]
0.051 [1.3]
30 [762]
0.032 [0.8]
0.042 [1.1]
0.052 [1.3]
0.062 [1.5]
35 [889]
0.038 [1.0]
0.049 [1.2]
0.061 [1.5]
0.072 [1.8]
40 [1016]
0.043 [1.1]
0.056 [1.4]
0.069 [1.8]
0.082 [2.1]
To reduce the size of the mounting bolt clearance hole it is recommended to offset the bolt
circle on the brake disc inwards the required amount for radial clearance. The end result is
the brake disc will have a slightly smaller bolt circle than the hub and the required radial
clearance will be on the side where it is needed.
Do not use fitted bolts for installing brake discs. The bolt holes must
be over sized to permit uninhibited expansion.
Do not secure a brake disc to a rotating element by welding.
Do not paint the cooling fins of a ventilated disc. The cooling
efficiency will be compromised, and overheating may result.
If the disc was damaged during installation with nicks or welding marks, remove the defects
before putting into service.
For cases where a disc guard or some protective cover is required for a ventilated disc ensure
that the guard does not compromise the performance. An improperly designed cover or
shield may cause air recirculation through the disc or radiant heat reflection, which could
result in the disc overheating. The cooling air pumped through the disc must be exhausted
away from the outer diameter of the disc to allow fresh, cool air to enter the inner vent
opening of the disc.
