The study concerning the contact between a tyre and the road surface was conducted in three phases. In the first phase the first and second-order factors were separated. The factors: type of road surface, tyre type, tread depth, water depth, tyre pressure and tyre load were included in an experimental multifactor investigation. Each of them appeared to affect the brake and sideway forces. Only the influence of the tyre pressure and load was found to be insignificant or very small. The second phase served to determine the numerical influence of the road surface characteristics and the speed on the size of the brake and sideway forces. It was found possible to compile a mathematical relation incorporating the contribution of the macro-roughness and micro-roughness of the road surface and also of the speed to the brake and sideway forces. In the third phase a similar mathematical relation was drawn up for truck tyres. Finally, recommendations are made for official measures, with emphasis on standards to be met by the macro-roughness and micro-roughness of road surfaces.
Abstract