Test Values/Wear Limits
Information
Depending on the wear of cast iron brake discs, two condition criteria can make replacement necessary:
- Cracking in the holed (perforated) brake disc friction plates is in an advanced state.
- Minimum brake disc thickness is not retained due to wear (material erosion due to friction).
| Location | Description | Type | Basic value | Tolerance |
|---|---|---|---|---|
| Pad thickness, front | Measured value | 12 mm | ||
| Pad thickness, front (wear limit) | Measured value | 2 mm | ||
| Pad thickness, rear | Measured value | 10.3 mm | ||
| Pad thickness, rear (wear limit) | Measured value | 2 mm | ||
| Brake disc thickness, new (front) | Measured value | 34 mm | ||
| Brake disc thickness, new (rear) | Measured value | 20 mm | ||
| Brake disc wear limit, front | Measured value | 32.0 mm | ||
| Brake disc wear limit, rear | Measured value | 18 mm | ||
| Maximum surface roughness of brake disc after machining | Measured value | 0.006 mm | ||
| Maximum thickness tolerance of brake discs | Measured value | 0.02 mm | ||
| Maximum lateral runout of brake disc | Measured value | 0.03 mm | ||
| Maximum lateral runout of wheel hub | Measured value | 0.03 mm | ||
| Maximal lateral runout of brake disc when installed | Measured value | 0.06 mm | ||
| Push-rod play | Measured at brake pedal plate | Measured value | approx. 1 mm | |
| Diameter of parking-brake drum | Parking brake (electrically actuated, drum brake acting on the rear axle) | Diameter | 180 mm | |
| Diameter of parking-brake drum, wear limit | Diameter | 181 mm | ||
| Width of parking-brake shoe | Measured value | 24 mm |
Possible complaints:
- Damage due to lack of use (rusting). This causes vibrations in the steering wheel, noises and brake pedal pulsation.
- Brake disc becomes distorted as a result of serious driving, e.g. on a racing circuit.
- Too much lateral runout when new brake discs are fitted on dirty or warped wheel hubs.
Procedure:
- Check brake disc for cracks, minimum thickness, lateral runout, thickness tolerance, flatness and surface roughness.
- Brake discs must not be machined. Replace worn brake discs in pairs and install new brake pads.