Test Values And Wear Limits For 18-Inch Brake System (Cayenne Basic Model/Cayenne Diesel (Except For USA))
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Information
Depending on the extent of wear on cast iron brake discs, two condition criteria can make replacement necessary:
- Formation of cracks at advanced stage on the brake disc friction surfaces .
- Minimum brake disc thickness is not retained due to wear (material erosion due to friction) . → 46500200 CHECKING FRONT BRAKE DISCS (WEAR ASSESSMENT) → 46530250 CHECKING REAR BRAKE DISCS (WEAR ASSESSMENT)
| Location | Description | Type | Basic value | Tolerance 1 | Tolerance 2 |
|---|---|---|---|---|---|
| Pad thickness, front | Wear limit 2 mm | approx. 9.7 mm | |||
| Pad thickness, rear | Wear limit 2 mm | approx. 8.8 mm | |||
| Brake disc thickness, front | New | 34 mm | |||
| Brake disc thickness, rear | New | 28 mm | |||
| Brake disc minimum thickness after machining, front | Only as-new brake discs may be reworked! Only rework the brake disc symmetrically, evenly from both sides! |
33.6 mm | |||
| Brake disc minimum thickness after machining, rear | Only as-new brake discs may be reworked! Only rework the brake disc symmetrically, evenly from both sides! |
27.6 mm | |||
| Brake disc wear dimension, front | 32 mm | ||||
| Brake disc wear dimension, rear | 26 mm | ||||
| Peak-to-valley surface roughness of brake disc after machining, max. | 0.006 mm | ||||
| Thickness tolerance of brake discs after machining, max. | 0.02 mm | ||||
| Lateral runout of brake disc, max. | 0.03 mm | ||||
| Lateral runout of wheel hub, max. | 0.02 mm | ||||
| Lateral runout of brake disc when installed, max. | 0.06 mm | ||||
| Pushrod play | Not adjustable | ||||
| Parking brake (foot-operated parking brake) | Drum brake acting mechanically on both rear wheels | ||||
| Parking-brake drum Ø | Wear limit 211 mm | 210 mm | |||
| Brake shoe width | 30 mm | ||||
| Brake pad thickness | Wear limit 1 mm | 3 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.
- Too much lateral runout when new brake discs are fitted on dirty or distorted wheel hubs.
Procedure
- Check brake disc for cracks, minimum thickness, lateral runout, thickness tolerance, flatness and surface roughness.
- If necessary, (depending on the actual brake disc thickness and the brake disc wear limit) machine the brake disc using one of the disc brake dressing machines approved by Porsche.
- The brake disc must only be reworked symmetrically, i.e. evenly from both sides! Read the operating instructions for the disc brake dressing machine!