The investigation deals with the difference in friction characteristics on ice between studded winter tyres, summer tyres and non-studded winter tyres including "friction tyres" not designed for studs. The study deals also with (1) factors to be considered in the development of new regulations concerning studs such as the number, protrusion and wear, (2) the indirect improvement of friction on ice also for non-studded tyres from the roughening effect on the ice by the studs, (3) the influence of speed on friction on ice for tyres with and without studs and (4) comparison between friction data on ice measured with four different types of equipment (BV12, BV11, passenger car, and the VTI stationary stationary tyre test facility). The results indicate that the improvement in friction on very slippery ice with studded tyres can bring about a reduction of the braking distance to half its value without studs. Friction caused by the studs increased with the number of studs and their protrusion and decreased with wear. Roughening of the ice by studs improved friction considerably. Speed had little influence on the friction level. The results with different test equipments were similar under equal conditions. (A).
Samenvatting