Kan dubbdäck på cykeln minska singelolyckorna?: friktionstester av cykeldäck i VTI:s stationära däckprovningsanläggning

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The purpose of this project was to define a useful methodology for comparing the ice grip of different bicycle tyres and to perform initial measurements. The long term objective is to set up recommendations to winter cyclists regarding bicycle tyres based on measurements performed according to the defined methodology. Measurements were done on smooth slippery ice using two regular (non-studded) bicycle tyres and four studded tyres of different brands and models. The tests were carried out in the VTI tyre test facility (TTF). The TTF is a unique indoor flat track machine for tyre tests on ice or asphalt pavement. This construction enables measurement of frictional forces under controlled conditions both when braking and steering. The TTF has been used for several years when testing tyres for both passenger cars and heavy vehicles, but to be able to test bicycle tyres some modifications of the equipment were necessary. The defined test method proved to be suitable for comparing studies. The measurements showed that studded tyres improve the grip on ice compared to regular bicycle tyres, but there can be differences in performance between different types of studded tyres. A larger number of studs is not necessarily related to a better grip on ice. When braking with locked wheel the frictional forces measured, were up to 2.5 times higher with a studded tyre compared to a non-studded tyre. In addition, studded tyres generally generate greater frictional forces when steering on ice compared to non-studded tyres. In general, a lower tyre pressure slightly increases braking and steering forces, but an optimal tyre pressure might be necessary in order to achieve the best possible performance from a studded bicycle tyre. Based on the results so far, cyclists should be recommended to use studded tyres when cycling during winter conditions. With an improved grip on ice and a better braking stability, there are safety benefits to be made.

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