Checking Grey Cast-Iron Brake Discs - Evaluating Cracks

No need to replace brake disc as the perforation crack length is small (less than 5 mm)  .

Fig 1: Identifying Front Brake Discs Crack

Courtesy of PORSCHE CARS NORTH AMERICA, INC.

Some perforation cracks are over 7 mm long.

Brake disc must be replaced (maximum permitted perforation crack length is 5 mm)! 

Fig 2: Identifying Front Brake Discs Crack

Courtesy of PORSCHE CARS NORTH AMERICA, INC.

Brake disc with cracked friction plate rim -arrow-  . Brake disc must be replaced! 

Fig 3: Locating Damaged Friction Plate Rim

Courtesy of PORSCHE CARS NORTH AMERICA, INC.