Checking Rear Brake Discs (Minimum Thickness)

Information 

Normally, brake discs are used until the maximum wear dimension is reached. → WM 4600TW TECHNICAL DATA/TEST VALUES AND BRAKE WEAR LIMITS  Only in a few exceptional cases is it advisable to skim the brake discs (if there is deep scoring or corrosion of the friction surface). In this case only the disc brake dressing machines approved by Porsche AG are to be used .

• Only as new brake discs may be reworked! 
• Only rework the brake discs symmetrically, evenly from both sides! 

As the pressure force of a brake piston on the brake pad varies in magnitude, different areas of wear arise on the friction surface. The brake disc can basically be divided into two areas of wear:

1. -A-  Outer and inner wear areas.
2. -B-  Central wear area.

Fig 1: Identifying Rear Brake Discs Wear Areas (A And B)

Courtesy of PORSCHE CARS NORTH AMERICA, INC.

The central wear area -B-  is the area with the highest degree of wear.

Fig 2: Identifying Rear Brake Discs Wear Area (B)

Courtesy of PORSCHE CARS NORTH AMERICA, INC.

• Measure the brake discs with a suitable micrometer at a minimum of three different places (-A, B, C-)  , offset by 120°.
  Fig 3: Identifying Measurement Points For Brake Disc Thickness

  Courtesy of PORSCHE CARS NORTH AMERICA, INC.