Checking Brake Discs For Minimum Thickness: Notes

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In the presence of high pressure forces, at the innermost and outermost hole-free friction plate track (-arrows- in Fig 1 ) 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 amount of pressing on the surface 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- . See Fig 1 .

Arrows: Zone where most wear occurs in brake disc friction surface

A: Perforation friction zone (holed friction zone)

B: Smooth friction rim zone

Fig 1: Locating Innermost And Outermost Hole-Free Friction Plate Track (Rear Brake Discs)

Courtesy of PORSCHE OF NORTH AMERICA, INC.

NOTE:

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. See Fig 2 .

Fig 2: Locating Brake Discs Thickness Measuring Point (Rear Brake Discs)
Courtesy of PORSCHE OF NORTH AMERICA, INC.
Brake disc thickness/wear limit: Max. 2.0 mm total wear permissible. Refer to the technical data for the new dimension and other dimensions Refer to TECHNICAL DATA/BRAKE WEAR LIMIT - BOXSTER S .

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). See Fig 2 .