Why buy winter tires? For many Canadians, buying winter tires is what's called a “grudge purchase” — we don't really want to lay out the money unless we really have to. Aside from places where swapping in proper winter tires is the law, that means that we can be lulled into a false sense of security by the “all-season” rating of the tires that we drive on the rest of the year. It gets even worse when you're talking about all-wheel-drive or four-wheel-drive vehicles, where manufacturers tout clever limited-split differentials, torque-vectoring capabilities, anti-lock brakes, and complex stability controlling systems. Cars are getting cleverer — why can't we have one type of tire to handle all conditions and let the electronics sort it out?
What's wrong with all-seasons? You might remember an old Pirelli advertisement from the ‘90s, featuring Olympic gold medal sprinter Carl Lewis crouched in the starting blocks, wearing a pair of high heels. The tagline said it best: “Power is nothing without control.” You can have the best on-board traction systems in the business, but it's not going to matter unless your car has the right shoes on. We're not just talking about snowy conditions either; when the air temperature starts dropping below seven degrees centigrade, it's time to start thinking about making the switch to your car's winter boots. That's when your all-seasons start stiffening up and losing traction. Remember: when you can see your breath in the air, think about the tires your car wears.
Compounds Wondering how exactly four round black rubber things can differ so much in the way they handle cold weather, rain, slush, black ice and snow? All tires aren't created equal. Yes, they're all made of rubber, but down at the molecular level things start getting very different. The molecules that make up a tire, called polymers, can either be synthetic or natural, or a blend of the two. They're manufactured to be springy and elastic, able to be filled with air and work like a tough-skinned balloon for your wheel, maximizing the amount of rubber in contact with the road.
Compounds Trouble is, different polymers have different operating temperatures. At a certain point, they start losing their flexible, rubbery nature and harden up. The technical term for this is the “glass transition temperature,” and it can be visualized by imagining what happens to a child's plastic bucket that's left out in a cold snap – it gets brittle, and can break if you drop it. The same thing happens to tires, to a lesser degree. They're not going to shatter, but they do start losing their springiness [at around seven degrees C for all-seasons]. Winter tires are designed to be softer at lower temperatures in order to maintain that grip on freezing ground. Why not simply use soft-compound tires all year round? Simple: when summer temperatures hit, the rubber compound gets so soft it wears out very quickly.
Tread The second part of what makes winter tires so effective, and something manufacturers spend a fortune on developing, is their tread patterns. You can actually hear and see the difference between a snow tire (right, in the photo above) and a summer tire, whether it's the clearly-visible knobbly design, or the rumbling noise they make as you drive down the highway. Imagine starting off on the extreme end of the tire spectrum with a soft racing slick (with no tread). This maximizes the contact area, but when it rains, can't evacuate the water. A rain tire adds grooves to help channel the water through rather than hydroplaning over it. Drive it in snow, and the narrow rain-channels soon get packed with icy debris, turning the tire right back into a slick! Time to add more – and better – channels. The rugged look of a dedicated snow tire comes down to the increased number of grooves and channels – known as “sipes” – in its surface. The more sipes, the theoretically better the tire is at handling deep snow and slush. However, that doesn't mean it's necessarily the best tire choice.
Choosing the right tire We spoke to Melissa Arbour, head of Canadian Tire's tire, wheel, and accessory division about what kinds of tires are best. “If you are driving in snow, I would likely suggest the General Altimax Arctic. If you drive on a lot of ice, the Michelin Xice Xi3 is an excellent choice. Or if you are looking for a tire with good performance and a comfortable and quiet ride (for longer drives), I would suggest the Goodyear Nordic Winter tire. Overall, our most popular one would be the Goodyear Nordic Winter tire.”
The right side of the scale Canadian Tire recently had their range of tires tested by an independent third party, and now offers a ten-point scale to help you gauge whether the tire you're looking at is the right blend of cold weather performance, in-snow capability and on-ice traction. Whatever choice you make – whether it's for a longer-wearing cold-weather tire for your daily commuter or a dedicated snow tire that turns your SUV into an unstoppable winter-proof snowmobile – you'll be far better off than the car stuck on the side of the road with all-season-tires.