Within the contact zone between tire and road all normal and tangential forces have to be transmitted. The tread block is the only tire component which is in direct contact to the pavement and therefore of special interest. The rolling process of a tire can be seen as a chronology of single contact events between tread block and road surface, whereas the contact situation in detail is usually unknown. The surface texture of the pavement comprises a large range of surface wavelengths which leads to a small area of real contact and to complex contact conditions. Under braking and acceleration procedures sliding friction occurs within the footprint especially at the trailing area of the contact zone. The tangential forces strongly depend on the contact conditions, e.g., surface texture, sliding velocity, normal contact pressure, temperature, tread block geometry, and existence of a lubrication film. An intermediate layer not only simply lowers the friction coefficient but also the whole contact situation changes. This effect is considerably existent for siped tire tread blocks which react in a different manner compared to nonsiped tread blocks. Within this publication the dynamics of siped tread blocks in contact are analyzed and a mechanical model will be presented to explain the observed phenomena. The simulation results are verified by experiments.

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