Cayenne (9PA) V6-3.2L (2006)
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Larger cracks impair braking comfort and reduce brake disc strength, therefore making brake disc replacement necessary as a precaution.
Irrespective of the crack length, the brake disc must be replaced if the crack has extended as far as the outer and/or inner edge of the disc.
Bedding in the brake pads and brake discs
New brake pads require a bedding-in period of approximately 200 km! Not until then do they achieve their best friction and wear coefficient. During
this period, the brakes should be subjected to full stress when traveling at high speed only in emergencies. The slightly reduced braking effect must be
compensated for by increased pressure on the brake pedal. The same also applies after replacing or machining brake discs.
Checking rear brake discs (evaluating cracks)
Different vehicle types have different brake disc sizes. This produces differences for the maximum crack length limits.
The maximum crack length limit is calculated as follows:
0.5 x a (-a- = width of friction surface in mm).
The length of a crack can be measured with a steel rule, for example. -steel rule-
Note:
Irrespective of the crack length, the brake disc must be replaced if the crack has extended as far as the outer and/or inner edge of the disc.
As a precaution, brake discs must be replaced when:
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the Maximum crack length: 0.5 x a mm (a = friction surface width in mm) is exceeded!
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the Maximum crack width: 1 mm is exceeded!
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the Maximum crack depth: 1.5 mm is exceeded!
Checking rear brake discs (minimum thickness)
Note:
Normally, brake discs are used until the maximum wear dimension is reached. Only in a few exceptional cases is it advisable to skim the brake discs
(if there is deep scoring or corrosion of the friction surface). In this case only the disc brake dressing machines approved by Porsche AG are to be used
(see Workshop Equipment Manual, Chapter 3.4).
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Only as new brake discs may be reworked!
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Only rework the brake discs symmetrically, evenly from both sides!
As the pressure force of a brake piston on the brake pad varies in magnitude, different areas of wear arise on the friction surface. The brake disc can
basically be divided into two areas of wear:
