Checking Rear Brake Discs (Evaluating Cracks): Notes

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:

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. -rule- 

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!