Checking Grey Cast-Iron Brake Discs - Minimum Thickness

Information 

• Replace brake discs once the maximum wear dimension has been reached. 
• Re-machining of brake discs is not permitted! 

Information 

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 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: Outer and centre wear areas.

The natural balance between stronger and weaker braking ensures that in almost all cases the typical wear profile of a perforated (cross-drilled) brake disc (friction plate) arises.

This means: the inner and outer smooth friction edge zone is most worn. 

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Outer wear areas

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Centre wear areas

Information 

Unlike smooth brake discs, on which the minimum thickness is measured in the middle of the disc, the minimum thickness of perforated (cross-drilled) brake discs must always be measured on the inner and outer friction surface track that is most worn -arrows-  .

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Wear areas A and B

Information 

The brake disc thickness tolerance can be found under Technical data/brake wear limits.

> 4600TW GREY CAST-IRON BRAKES - TECHNICAL VALUES AND WEAR LIMITS 

1. Measure brake disc thickness. 

   Measure the brake disc thickness -X-  in the area of the outer or inner friction surface toe -Arrows-  on at least three different points (-A, B, C-  ) offset by 120°.

   To do this, use a suitable micrometer screw or a brake disc gauge.

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   Measurement points for brake disc thickness