Checking front brake discs (evaluating cracks)

Different vehicle types have different brake disc sizes. This produces differences for the maximum crack length limits.

The maximum crack length limit is calculated as follows:

Fig 1: Width of friction surface a

Courtesy of PORSCHE OF NORTH AMERICA, INC.

0.5 x a (-a-  = width of friction surface in mm). See Fig 1.

Fig 2: Brake discs

Courtesy of PORSCHE OF NORTH AMERICA, INC.

The length of a crack can be measured with a steel rule, for example. -steel rule-  . See Fig 2.

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!