Checking Brake Discs For Minimum Wear Value

Information 

The pictures shown in this document may differ from the original. 

Information 

• PCCB brake discs must be checked for wear during every service and whenever the brake pads are changed! Brake disc remains installed. 
• Carry out wear assessment on the brake discs and check the condition of the brake pads before and after every race track use (component temperatures are significantly higher than temperatures during "normal" driving). 
• The brake disc temperature must be in the range between 0 and 40 °C during the measurement. 
• Check tester before taking measurements and calibrate it if necessary. Follow the operating instructions provided by the equipment manufacturer! 
• Position tester on the brake disc. 
• Take measurements at three points marked on the brake disc hub. 
• Quick measurement with brake calliper fitted. 
• Exact measurement in this area with brake calliper removed. 
• If the measured value is more than 5 units above the wear value, the quick measurement is sufficient. If the measured values are smaller, remove the brake calliper and perform an exact measurement. 
• Note on quick measurement: A metallic heat shield will lower the measured value. 

1. Measure values using test equipment for PCCB brake discs WE 1578  at the three marked measuring points, -arrows- with the brake disc installed  .

   The following description distinguishes between quick measurement (as in 2.) and exact measurement (as in 3.). 

   Fig 1: Locating Friction Markings With Friction Coating Technology

   Courtesy of PORSCHE CARS NORTH AMERICA, INC.

   Information 

   • The drop in the value using a brake pad set depends very much on the driving conditions. 
   • The remaining service life of the brake disc can be estimated using the previously stored data and measured values recorded during service intervals/workshop visits based on the mileage. 
   • On the 911 Turbo/911 GT3, the value is reduced by 2 to 5 units per brake pad set (depending on the axle and brake pad). Not valid for race track use and if brake pads not approved by Porsche are used. 
   • Carry out wear assessment on the brake discs and check the condition of the brake pads before and after every race track use (component temperatures are significantly higher than temperatures during "normal" driving). 
2. Quick measurement:  Brake calliper fitted (with or without wheel).
   Fig 2: Measuring Brake Calliper Wear Condition

   Courtesy of PORSCHE CARS NORTH AMERICA, INC.
   1. 2.1. Measuring procedure: Align laser beam -2-  onto the measurement marking on the brake disc hub.
      1. Test equipment VAS 6813
      2. Laser beam for positioning
      3. Measured value display
         Fig 3: Positioning Tester On Brake Disc

         Courtesy of PORSCHE CARS NORTH AMERICA, INC.

      When taking measurements, the tester must be positioned over the entire surface of the brake disc with the roller stops and the underside of the device.

      Fig 4: Locating Roller Stops

      Courtesy of PORSCHE CARS NORTH AMERICA, INC.
   2. 2.2. Compare the values you read off with the wear value -3-  (lower value).

      If the wear value (lower value) is reached or if the measured value is less than the wear value at a measuring point, carry out an exact measurement. 

      Fig 5: Identifying Brake Disc Markings And Values

      Courtesy of PORSCHE CARS NORTH AMERICA, INC.
3. Exact measurement: Wheel and brake calliper removed. 

   Turn the measurement marking and brake disc so that the tester can be placed at the position at which the brake calliper was removed.

   The removed brake calliper must not be placed closer than 50 mm to the back of the brake disc when taking measurements.

   Always follow the operating instructions for the tester to make sure you are using it correctly. 

   1. 3.1. Measuring procedure: Align laser beam -2-  onto the measurement marking on the brake disc hub.
      1. Test equipment VAS 6813
      2. Laser beam for positioning
      3. Measured value display
         Fig 6: Positioning Tester On Brake Disc

         Courtesy of PORSCHE CARS NORTH AMERICA, INC.

      When taking measurements, the tester must be positioned over the entire surface of the brake disc with the roller stops and the underside of the device.

      Fig 7: Locating Roller Stops

      Courtesy of PORSCHE CARS NORTH AMERICA, INC.
   2. 3.2. Compare the values you read off with the wear value -3-  (lower value).

      If the wear value (lower value) is reached or if the measured value is less than the wear value at a measuring point, replace the brake discs on each axle.

      Applies to exact measurement (not quick measurement). 

      Fig 8: Identifying Brake Discs Markings And Values

      Courtesy of PORSCHE CARS NORTH AMERICA, INC.