Test Values And Wear Dimensions - 18-Inch Brake System (V6 (Usa Only)/V8S/V6 Hybrid/V6 Diesel Bin5/V8 Diesel/GTS)
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Information
Depending on the extent of wear on grey 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).
| Location | Description | Type | Basic value | Tolerance |
|---|---|---|---|---|
| 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 | 36 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! | 35.6 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 | 34 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. For a list of recommended disc brake dressing machines, see Workshop Equipment Manual, Chapter 3.4.
- The brake disc must only be reworked symmetrically, i.e. equally from both sides! Observe the operating instructions for the disc brake dressing machine!