Quote:
Originally Posted by underscore
I believe summers and all seasons start to lose grip below 7*C, personally I swap to winters as soon as I'm going to be doing any driving in single-digit (below 10*C) weather.
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The 7°C thing came from Continental Tires and Nokian Tires years ago with a comparison of their summer tires and winter tires at various temperatures on wet and dry pavement for Auto Express magazine. They never compared all season tires and I've yet to see a study that actually shows that winter tires perform better than all seasons at above freezing temperatures in all conditions. But this has been repeated ad nauseum, most notably by Canadian Tire. The same comparison also showed the summer tire was substantially better in terms of braking and handling as temperatures rise above 7°C (plus wear and fuel consumption also increased substantially on the winters).
In fact, some sources generally rate good all seasons better in rain and slush (obviously winters substantially better in snow and ice), citing better designs for siping away water.