Checking front brake discs - evaluating cracks

Different vehicle types have different brake disc sizes. This results in differences in terms of maximum crack length limits.

The maximum crack length limit is calculated as follows:

0.5 x a (-a-  = width of friction surface in mm).

The length of a crack can be measured with a steel rule, for example. → Brake discs 

Information 

Irrespective of the crack length, the brake disc must be replaced if the crack has extended as far as the outer and/or inner edge of the disc.

As a precaution, brake discs must be replaced when:

• the → Maximum crack length: 0.5 x a mm  (a = friction surface width in mm) is exceeded!
• the → Maximum crack width: 1 mm  is exceeded!
• the → Maximum crack depth: 1.5 mm  is exceeded!