Winter tires can't take heat of spring and summer

Winter, all-season and summer tires are built for different temperatures.

  • Male mechanic working on wheel of car

The sun is shining, the robins are singing, and the winter tires are starting to howl.

Perhaps your winter tires are telling you something.

Once the average daily temperatures are over +7C, it is time to make the changeover to summers or all-seasons. Self-preservation should be the motive: the changeover may help you avoid a collision or a blowout.

All classes of tires — winter, summer and all-season (really three-season) — start life with quite different rubber compounds. Each is optimized for a different temperature range. If we run a tire outside of its comfort zone, it reacts badly.

Summer tires in winter turn hard as hockey pucks; in winter, all-season tires start to lose grip as temps drop below +7C and are virtually useless for grip below -10C. Winter tires lose grip as the temperatures climb above +7 C. Just as all-seasons wear tread faster in winter, winters wear faster in summer.

Winter tires are constructed to have flexible tread below freezing and they have lots more tread blocks with many sipes for ice grip. These elements do not work in warm weather. In fact they are counterproductive. As the tire rotates, the tread blocks come into contact with the pavement and heat is created as the block is compressed. The sipes open and close as they come into contact with the pavement and create more heat.

Heat is the worst enemy of a tire. This heat makes the tread blocks more flexible, which in turn creates more tread squirm, which in turn creates more heat, which in turn creates more squirm and so it goes. Heat in a tire causes the essential binding agents in a tire to break down. The tire will get a greasy feel because, in fact, it is chemically dissolving. Greasy tires do not grip.

For an emergency stop or collision avoidance lane change, we need all available grip to keep us out of trouble. For maximum grip, we need a tire operating within its temperature zone. Panic stops place great stress on a tread block. It must be rigid and not wobble, to stay in full contact with the road.

Winter tires by design are engineered to be wobbly, to dig for traction in the snow. On pavement, this wobbly tread makes stopping distances significantly longer and the car harder to control.

Compare a winter tire and a good all-season tire. The winter tire will have two to three times as many tread blocks, and an infinite number more sipes. More tread blocks and sipes equal more heat.

Some multi-cell winter compounds (Bridgestone Blizzak, Yokohama Ice Guard) have tiny air pockets in the rubber. These air pockets make the tire squirm even more than other winter tires. This squirm creates extra heat.

Remembering that heat build-up is the main cause of tire blowouts should also make us want to change tires for warmer weather. Surveys show us that most Canadians do not check tire pressure regularly.

An underinflated winter tire generates even more heat than a properly inflated one. Once the heat builds up, the tire fails very suddenly and catastrophically.

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