All-Season Tires–Investigation of Braking Performance in Summer and Winter Conditions

All-season tires have previously not been allowed to use in Sweden during winter. However, after a recent change of regulations they are now valid as winter tires if they are marked with the 3PMSF symbol, indicating that the tire has passed a standardized snow grip test. Whether the compromise between summer and winter grip makes them unsuitable for Swedish road conditions is an open question. The purpose of this study was to test the road grip of all-season tires during winter and summer conditions and compare them to regular winter and summer tires. A total of 14 all-season tires were carefully selected, together with a few studless winter tires and summer tires. Braking tests were performed on ice and snow tracks, as well as on dry and wet asphalt. It is clear from the results that the performance spread is very large among the tested all-season tires, where some manufacturers aim for grip on asphalt and others on snow. In general, the snow grip is worse than traditional winter tires of both Nordic and central European type, and especially so for the three all-season tires that were not 3PMSF marked. The ice grip of all-season tires was without exception much worse than what has been seen before in similar winter tires tests performed by VTI, and one of the all-season tires performed equally badly as one of the summer tires. Correlations between rolling resistance and grip on the different surface conditions were investigated as well.