Service Life of Brake Friction Products
The service life of brake friction products and their wear behavior is only one, albeit important factor in their assessment. The formula and requirement conception of each brake friction product is a compromise between the following fundamental assessment criteria:
- Friction coefficient stability under all operating Conditions
- Comfort behavior (squealing, judder, responding behavior, etc.)
- Wear behavior
Extreme and one-sided requirements generally have a negative influence on the other factors involved.
Physically, the braking procedure itself is a process of dry friction and needs specific friction lining and countermaterial wear to maintain the effectiveness of the braking. An ongoing regeneration of the friction surfaces is achieved through this. Brake friction products are therefore typical wear parts, although their wear rate is influenced by many factors. These can be differentiated between and regarded as follows:
- Friction-material-related properties
The primary influence on the wear rate is the temperature range of the brake disc or drum as well as the speed range and thus the energy conversion during braking. Wear greatly increases at higher temperature ranges. Production or batch-related differences in wear behavior
are negligible compared to the other influencing factors.
- Operating conditions
Driving style (braking frequency, speed ranges), traffic conditions and topographical and climatic conditions have the greatest influence on wear behavior. Experience shows that it is mainly the driving style that decisively influences the service life of a brake friction product.
- Condition of the brake system
The brake system is exposed to the effects of dirt, moisture, chemical substances (e.g. salt) as well as high temperatures and mechanical forces. As it comprises
functionally important sliding parts, it requires regular maintenance. Seized or sluggishly moving parts can have a highly adverse effect on the functionality of the brake and on brake friction and counter-material wear. The condition of the brake disc or drum (surface, minimum thickness, geometrical form) is an equally decisive factor with regard to the function and wear behavior. In view of the above and assuming that the brake friction product is fully functional, service life of the brake friction product is in practice a statistical factor, whereby the distribution function for passenger cars shows that the upper service life values exceed the lower ones by a factor of 10-15.
This means a statistical mileage range of between
10,000 and 150,000 km
whereby in individual cases, the mileage may, of course, be below or above these limit values. For this reason, the manufacturers of brake friction products are unable to specify a definitive service life guarantee.