Rubber vs countersurface frictional behaviour : How this influences the traction of pneumatic tyres

The unique frictional behaviour of rubber is responsible for the ability of the pneumatic tyre to generate traction sufficient for vehicle control under a wide range of operational conditions. Unlike hard solids, the coefficient of friction (frictional force/normal force) between rubber and a clean hard countersurface can easily exceed 1.0. Under other conditions, ice near 0 deg C or at certain conditions on a wet highway, the coefficient can be near zero. After a brief survey of basic rubber friction theory, this wide range of traction capability (dry and wet pavements, ice and snow) is explained in terms of four frictional contact characteristics operating in the rubber countersurface interface. The relationship between these four characteristics and the major tyre and external factors that determine traction is established for the various environmental conditions. As with most complex systems, there is substantial interaction for the tyre (design) factors as a group and for tyre factors with external operational factors. The most important of these interactions are reviewed in addition to a discussion of traction capability under adverse or critical conditions where the maximum traction capability is needed.