Checking Pccb Brake Discs (Wear Assessment)

Information 

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Measurement markings with new friction coating technology

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Markings and values (new value/wear value)

• Validity (of measuring method using test equipment VAS 6813) for PCCB brake discs with new friction coating technology. Recognizable by the three markings and values lasered at an offset of 120° (on the brake disc hub) -arrows-  .
• VAS 6813 is used to measure the damage to the carbon fibre-reinforced material. The lower this value, the more carbon fibres in the internal structure of the brake disc are damaged (wear caused by the effects of temperature). 
• The markings consist of the measuring point numbers 1 to 3 -X-  (figure shows number 1), the measurement marking -1-  (line), the new value -2-  and the wear value -3-  .
• If one of the three wear values is reached or if the measured value is less than one of the three wear values, replace the brake discs on both sides of the axle. 

Information 

• Check PCCB brake discs for wear during every service and when changing the brake pads! Brake disc remains installed. 
• Always 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 between  >Temperature 0°C  and >Temperature 40°C when taking measurements. 
• The tester must be checked before taking measurements and may have to be calibrated. Follow the operating instructions provided by the equipment manufacturer! 
• Important for quick measurement: A metallic heat shield will lower the measured value. 

Information 

• 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. 
• The value is reduced by approx. 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). 

1. Determine the current wear condition using >VAS 6813 - PCCB Brake Disc Tester  .

   A differentiation is made between a quick measurement  (See  ) and an exact measurement (See  ).

   1. 1.1 Quick measurement:  Brake calliper fitted (with or without wheel).

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      Quick measurement with wheel

      1. 1.1.1 Align laser beam -2-  onto the measurement marking on the brake disc hub.

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         Positioning tester on brake disc

         1	Tester VAS 6813
         2	Laser beam for positioning
         3	Measured value display

         Information 

         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.

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         Measuring procedure/tester (roller stops)

      2. 1.1.2 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  (See  ).

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         Markings and values (values given as examples only)

   2. 1.2 Exact measurement:  Wheel and brake calliper removed.
      1. 1.2.1 Remove wheel

         > 440519 REMOVING AND INSTALLING WHEEL

      2. 1.2.2 Remove brake calliper

         > 473919 REMOVING AND INSTALLING FRONT BRAKE CALLIPER

         Information 

         Once removed, the brake calliper must not be placed closer than >Length 50 mm  from the back of the brake disc (see operating instructions supplied with the measuring equipment).

      3. 1.2.3 Align laser beam -2-  onto the measurement marking on the brake disc hub.

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         Positioning tester on brake disc

         1	Tester VAS 6813
         2	Laser beam for positioning
         3	Measured value display

         Information 

         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.

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         Measuring procedure/tester (roller stops)

      4. 1.2.4 Compare the values you read off with the wear value -3-  (lower value).

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         Markings and values (values given as examples only)

      5. 1.2.5 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 both sides of the axle

         > 465119 REMOVING AND INSTALLING FRONT PCCB BRAKE DISC 

2. Visual inspection of the brake disc friction surfaces for surface changes.
   1. 2.1 Check for build-up on brake disc friction surface. If there is a build-up on the pad, also check the following points:
      • Check ventilation (brake cooling): All components are present, secured correctly and undamaged.
      • Check brake pad quality: Use the appropriate brake pads if the vehicle is being used on a racing circuit.
        NOTE: Work cannot be carried out on the bores in the brake disc friction surface 

        • Damage to brake discs 

          → Clean the bores on PCCB brake discs with high-pressure cleaning equipment if necessary. Observe the relevant environmental and safety regulations.

          → Do not machine the bores. Drilling or counter-sinking is not permitted.

        The perforation bores in the brake discs must not be blocked. Clear them if necessary.

   2. 2.2 Check brake disc for flaking/fractures as a result of unusual usage conditions (e.g. stone chip damage). Flaking/fractures are only permitted up to a size of >Area 1 cm ²  !

      Information 

      The surface roughness affects braking comfort (noises), braking behavior/pedal pressure and brake pad service life.

   3. 2.3 Check surface roughness Sr (max. >Roughness depth 80 μm  permitted) on brake disc.

   Information 

   • Irrespective of wear, a brake disc may need to be changed due to edge damage on the brake disc friction surfaces. 
   • In this case, only one brake disc can be replaced if the measured value (determined using test equipment VAS 6813) and the friction surface of the other PCCB brake disc are still perfectly OK. 
3. Check brake discs for edge damage -see figure-  (damage due to improper use).

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   Edge damage on PCCB brake disc (shown as an example)

   • Max. permitted width/depth = >Width/depth 2 mm 
   • Max. permitted length = >Length 10 mm 
   • Max. 3 damaged edge areas permitted