a detailed investigation has been made of the skidding resistance of smooth and patterned tyres with different treads of seven polymers. the tyres were tested over a very wide speed range (1 to 140 km/h) on eight test track surfaces characterised by different micro and macro textures. these tests formed part of a road and laboratory programme to investigate the complex visco-elasto hydrodynamic mechanism of tyre/wet road friction. in practice it was found that the effects of extremes of surface are greater than the extremes of tyre tread polymer and pattern combined. though all factors can play a part in providing good tyre/road grip in wet conditions the relative importance of the tyre and road surface texture reverses over the practical motoring speed range. it appears that hysteresis alone does not account for the high skidding resistance measured on some surfaces at high speeds but that the sequence of events arising from hysteresis losses on rough surfaces creates tyre/road contact conditions corresponding to lower speeds so that adhesion becomes directly and hysteresis indirectly responsible for the increased skidding resistance. (a)

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