Functional test of the brake caliper adjuster - The right twist

With this innovative set of indicators for checking the function of pneumatic disc brake adjusters, Knorr-Bremse TruckServices offers another practical aid for everyday workshop work.

Playing with distance

With disc brakes, adjusters ensure that the distance between the brake pad and the brake disc - the so-called clearance - is always at the optimum mean value. The gap must not be too small so that the disc can really rotate freely when released and does not overheat. It must not be too large in order not to unnecessarily delay the onset of the braking effect and thus increase the braking distance. Without an adjuster, the clearance would increase due to wear on the brake pads and brake disc. During each braking process, the adjusters therefore compensate for changes in the clearance by readjusting the threaded tubes in the brake caliper accordingly.


  • Based on suggestions from workshop technicians
  • Developed in cooperation with leading manufacturers of special tools
  • Easier, safer, faster and more cost-effective maintenance and repairs
  • Continuous expansion of the tool programme

Functional testing made simple*

Checking that the adjuster is functioning properly is one of the standard activities in the workshop. Using the new indicator tool kit (K219632K50) from TruckServices, it can now be done even faster: Simply place the appropriate indicator on the adjuster, apply the brake five to ten times and see whether the adjuster function is working correctly based on the movement of the arrow-shaped indicator.

Correct operation of the adjuster is visible when the indicator continues to rotate in small steps with each brake application. As the number of actuations increases, the incremental movement of the indicator decreases. If the indicator does not rotate at all, only on the first application or moves backwards and forwards with each application, the adjuster is defective and the brake calliper should possibly be replaced.


Before using the indicator, turn the adjuster with the adapter 3 clicks anti-clockwise. Then remove the adapter. Please always note the information in the corresponding service instructions for the brake when carrying out maintenance work. Depending on the installed adjuster, the end position of the indicator may be different on individual brakes when testing several brakes (no synchronous movement). This is not an indication of  malfunction of the adjuster.

This animation illustrates the use of the indicator tool and which movement indicates a correct or incorrect functioning of the adjuster or caliper. The description refers only to Knorr-Bremse disc brakes. It may differ for disc brakes of other brands. Please observe the instructions of the respective vehicle and axle manufacturer.

Indicators for disc brakes of all common manufacturers

The tool kit consists of five indicator types in different colours, which allow the adjuster function to be checked not only for Knorr-Bremse disc brakes, but also for disc brakes from other manufacturers. The set contains each indicator type twice. This means that both brakes on an axle can be tested in one test run. The test can thus be completed more quickly overall.

Adjuster Indicator Tool Kit

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