Testing the thickness difference of a brake disc | HELLA

General information

When carrying out troubleshooting on the brake system, test procedures may be required, such as checking the thickness difference (varying disc thickness) of the brake disc. The thickness difference can only be tested using a suitable measuring tool.

A micrometer screw provides sufficient measuring accuracy of ± 0.001 mm.

The maximum permissible thickness difference is 0.015mm.

This test should only be carried out on brake discs that have been normally worn or are like new.

Testing the thickness difference of a brake disc - Image 1

Tests

The following procedure is recommended.

1. Prepare the brake disc for testing. If necessary, disassemble the brake caliper and brake caliper carrier for this

2. Clean the friction surfaces of the brake disc

3. Determine the thickness of the brake disc at various measuring points around the brake disc, approx. 10 – 15 mm beneath the external friction radius

4. Note the measured values and compare

The difference between the smallest and greatest measured value is the thickness difference.

Testing the thickness difference of a brake disc - Image 2

Repair note

Depending on the vehicle type, a thickness difference of as little as 0.015 mm can lead to brake judder.

Please observe the specifications in the maintenance and repair notes provided by the respective vehicle manufacturer.

Technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their day-to-day work. The information provided on this website is intended for use by suitably qualified personnel only. Reprinting, distribution, reproduction, exploitation in any form or disclosure of the contents of this document, even in part, is prohibited without our express, written approval and indication of the source. The schematic illustrations, pictures and descriptions serve only for the purposes of explanation and representation of the instructions and cannot be used as a basis for installation or assembly work. All rights reserved.