Checking Front Brake Discs (Evaluating Cracks)

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

Maximum crack length limit is calculated as follows:

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

Courtesy of PORSCHE CARS NORTH AMERICA, INC.

Width of friction surface a

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

Courtesy of PORSCHE CARS NORTH AMERICA, INC.

Brake discs

As a precaution, brake discs must be replaced when:

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.

• 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!