All-season tires were previously a tire category that did not exist on the Swedish market. After a rule change, the tire type was allowed in winter as of 2019.
In a unique research study, the Norwegian Road and Transport Research Institute (VTI) has investigated how all-year tires compare to winter and summer tires, by testing 14 different all-year tires in winter and summer.
Nothing further, it would turn out. The braking distance of the all-year tires was on average 10–30 percent longer on snow than the Nordic studless winter tire used as a reference. On ice, the braking distance was 25–50 percent longer.
“Are dangerous to traffic”
Traffic safety researcher Mattias Hjort at VTI was surprised by the result.
– I suspected that they would not be as good as pure winter tires, but I did not expect that some of them would be so bad on ice, says Mattias Hjort, who led the study.
All-year tires with low rolling resistance, which were developed to provide lower fuel or electricity consumption, had particularly long braking distances on ice.
– A large part of the all-year tires that we have tested are dangerous to traffic on Swedish winter roads, especially when it gets icy, says Hjort.
The all-year tires were also worse on dry and wet asphalt, with 5-30 percent longer braking distances than the summer tire used as a reference in the study.
Rubber and pattern
The difficulty in manufacturing a tire for all seasons lies in the fact that summer and winter road laws make different demands on the rubber compound and the tire pattern. Some of the tires in the test were clearly better on snow and ice than on dry or wet asphalt, and vice versa.
– It seems that different tire manufacturers have chosen completely different ways of looking at the matter. Some have produced a tire that is more like a pure winter tyre, while others have produced something that is more like a summer tyre, says Hjort.
He advises car owners who have already purchased all-season tires to replace them.
– If you have the opportunity to replace them, I think you should do so. I think you should drive on winter tires in the winter and summer tires in the summer, says Hjort.