The ways in which car tyres become worn in practice are - evenly, with one shoulder wear, with double shoulder wear or with centre wear. Peak and locked wheel brake force coefficients have been measured for both new tyres and those worn in these various ways. The tests were done on two research track surfaces representing the extremes of rough and smooth surfaces likely to be found on roads. Speeds ranging from 30 km/h to 125 km/h were used. The Motorway surface gave little difference for both locked or peak wheel conditions between the different tyres tested. On the Brush Concrete Surface there was little difference between the most worn tyres irrespective of the type of wear. Full details are given in the report. (A)

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