911 Turbo AWD F6-3600cc 3.6L SOHC Twin Turbo (1997)
The crack thickness has been highlighted (to make identification easier) and therefore the cracks better visible than they actually are.
2. Checking Brake Disc Minimum Thickness
Notes
Along the innermost and outermost friction disc tracks that have no holes, wear of the corresponding brake pad friction area is lowest - compared to
the center hole area - if the brakes are subjected to high contact pressures. As a result, less severe braking will lead to a corresponding increase of
surface pressure in these areas and, hence, to increased friction disc wear.
The natural ratio of heavy to light braking will produce the typical wear profile of a perforated friction disc in virtually every case (inner and outer,
smooth friction edge zone shows greatest wear. refer to illustration.
As opposed to smooth brake discs where the smallest thickness is measured in the disc center (effective frictional radius), the minimum thickness of
perforated brake discs must always be measured at the inner or outer track of the friction disc that is worn to the greatest extent.
Checking minimum brake disc thickness
Use a suitable micrometer to measure the smallest brake disc thickness at one of the two smooth friction edge zones (at the friction edge zone that
is worn to the greatest extent).
For the wear limit (minimum thickness), refer to the "Technical Data".
Example for area of greatest wear
The illustration shows the typical wear groove pattern (arrows) of a perforated 993 brake disc that was driven up to the wear limit under severe
long-term operation (test operation).
Important note on new brake pads
Due to the relative high abrasive action of perforated friction discs, the wear pattern of newly fitted brake pads will adapt itself relatively rapidly to
the wear pattern of the used brake disc. After introduction of optimized perforation patterns, the service life of perforated Porsche discs as well as
of brake pad materials is now almost equal to the service life of smooth discs.
