Since the introduction of the longer maintenance intervals of 25,000 km in March 2006, it has been necessary to check the brake lining thickness each time the vehicle is serviced. Depending on the degree of wear, an appointment for replacing the brake linings must be arranged with the customer or the brake linings must be replaced immediately.
The wear test must be performed as part of the "Customer interview" by means of a visual inspection with the complete wheel still fitted. During this test, the inner and outer brake linings on disk brakes and the lining thickness of the brake shoes on drum brakes must be checked in order to estimate a possible replacement date using additional data.
The section "Customer interview" has been added to the service sheet to allow the wear test results to be recorded.
Determine the remaining useful life of the brake linings:
1 Determine the total thickness (G) of the respective brake lining.
2 Subtract the non-usable area (V) of 3 mm from the measured total thickness (G) (G - V). This gives the usable remaining lining thickness (R).
3 Multiply the remaining lining thickness (R) by the appropriate wear factor (VF) (R x VF). The wear factor (VF) is 4,000 km/mm for the brake linings on the front axle and 6,000 km/mm for the brake linings on the rear axle. This gives the expected useful life in km.
Example:
If the determined total thickness (G) of the most severely worn brake lining on the front axle is 8 mm, the following calculation results:
8 mm - 3 mm = 5 mm
5 mm x 4,000 km/mm = 20,000 km
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The deterioration factor (VF) specifies the appropriate possible mileage for each millimeter of brake lining thickness at an average load. This figure is only intended as a guide. Depending on the driving style and conditions of use of the vehicle the remaining useful life may deviate from the value determined. In order to avoid unscheduled workshop visits, a premature brake lining change should be recommended to the customer for a calculated useful life < 25,000 km.
Since accessibility to allow visual inspection with the complete wheels still attached varies depending on vehicle and equipment, the wear test must be performed in various ways.
A folding mirror, a flashlight and a gauge are required for the test.
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Checking using gauge
Checking using flashlight
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Checking using flashlight and mirror
Checking drum brake at rear axle
Checking at inner floating caliper brake
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Brake pad test gauge