Porsche 996 TT, Repair Manual

Page: 1404 / 2099

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2. Checking brake discs for minimum thickness
Note
In the presence of high pressure forces, at the innermost and outermost hole−free friction plate track
−arrows−
, the brake pad friction surface is the least worn, compared to the middle holed area. As a
result, in the case of weaker braking, a relatively higher surface pressure arises in these areas and
therefore greater wear of the friction plates. The natural balance between stronger and weaker braking
ensures that in almost all cases the typical wear profile of a perforated friction plate arises (inner and
outer smooth friction rim area is the most worn) −arrows− .
•
As opposed to smooth brake discs, by which the minimum thickness is measured in the middle of the
disc (effective friction radius), in the case of perforated brake discs, the minimum thickness must be
measured on the inner or outer friction surface track, −arrows− whichever is most worn. •
Brake disc thickness/wear limit: Max. 2.0 mm total wear permissible. Refer to the technical data for
the new dimension and other dimensions ’ 46 Technical data/wear limits − Turbo or GT2 with gray
cast iron brake discs . •
Measure the brake disc thinnest point with a suitable micrometer screw, at one of the two smooth friction
rim zones −arrows− (at the most worn friction rim area).
The following drawing shows the typical grooved wear profile −arrows− of a perforated gray cast iron brake
disc, which has been used to the wear limit, under tough conditions i.e. constant operation mode (test
einordnung
2. Checking brake discs for minimum thickness 1341