Evaluating the cracks on the grey cast iron brake discs

The brake discs must be replaced (as a precautionary measure), if the perforation crack length is over 5 mm (as there is no mileage reserve in the event of further extreme load) and/or the friction plate rim is torn (less smooth braking and an increase in the likelihood that a disc will break)!
In the evaluation of damage, the following drawings must be used!

Corresponds to a disc exposed to above-average load.

Fig 1: Evaluating Cracks On Disc Exposed To Above-Average Load
Courtesy of PORSCHE OF NORTH AMERICA, INC.
- Need not be taken out of the vehicle!
In parts, perforation starter cracks are over 7 mm long. Conditions after shock braking 1,200 times (minimum desired: shock braking 200 times).

Fig 2: Evaluating Starter Cracks Over 7mm Long
Courtesy of PORSCHE OF NORTH AMERICA, INC.
- Brake disc can no longer be used!
Brake disc with torn friction plate rim -arrow-.

Fig 3: Identifying Brake Disc With Torn Friction Plate Rim
Courtesy of PORSCHE OF NORTH AMERICA, INC.
- Brake disc can no longer be used!