Where the rubber meets the road

Winter tires have come a long way from the chunky, off-road-ready snow tires of yesteryear. Advances in rubber compounds, tread patterns and tire construction have all come together in the last 15 years to ensure that drivers have the best equipment possible, no matter what vehicle they own.

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Winter tires have come a long way from the chunky, off-road-ready snow tires of yesteryear. Advances in rubber compounds, tread patterns and tire construction have all come together in the last 15 years to ensure that drivers have the best equipment possible, no matter what vehicle they own.

However, there’s still a sizeable chunk of the population who think that winter tires either cost too much, or that whatever rubber came with their vehicle is still an acceptable choice.

We’re all big believers of the benefits of winter tires. We’ve sampled winter, summer and all-season rubber back-to-back on the same roads and know that season-specific tires are always the right choice.

Nigel Mortimer, head of recalls for Transport Canada and a veteran Formula Ford racer, gives a reason that makes a lot of sense.

“If four good winter tires are installed, the traction differential between winter and summer roads is less than if the same tires are used all year,” says Mortimer. “Cold all-season tires have far less traction than cold winter tires due to the rubber composition of the tire tread.”

In other words, in cold conditions, winter tires allow handling characteristics to be more similar to performance tires in summer driving than all-seasons do. And, as winter roads can change every metre, ensuring predictable handling is just as important as outright grip.

Time machine

Back in the early years of true winter tires — i.e. the early ‘90s — complaints arose regarding excessive wear and iffy handling. Extensive development has curbed most of these objections.

The two main areas that helped a winter tire perform so well — a soft rubber compound and numerous sipes (thin lateral cuts that open and close, effectively expanding the contact patch) — were identified as the main culprits.

Stiffening up the winter tire’s response can mainly be attributed to offset or zig-zag style sipes, which actually lock together under load to reduce squidginess. These interlocked blocks mimic the larger tread blocks on regular tires, bringing more predictable handling to the segment.

The wear issue was resolved by replacing the traditional prime reinforcement material, carbon black, with silica. The sand-derived material brought about better elasticity in cold temperatures and better wear performance.

Also, the rubber compound varies in modern winter tires to further benefit integrity, grip and durability.

“Our current X-ice winter tire has two different compounds,” said Ron Margadona, Michelin’s product marketing manager. “On the top 60 per cent we can max out the softness of the silica compound. The underlying layer is of a higher stiffness compound.”

The industry seems to have settled on a three winter-season lifespan, or about 40,000 km, significantly improving the value of winter rubber.

There are also a myriad of things manufacturers throw into the compound soup in the ongoing search for more traction. While the ideal solution would be to use studded tires, they’re not legal for use in every part of Canada.

As a solution, Toyo uses crushed black walnut shells. “The shells work like tiny steel spikes which grab onto slippery surfaces,” said Ron Golab of Toyo Tire Canada. “Walnut shells are used because they are less harmful to the environment and are about the hardest natural substance.”

Toyo’s tread blocks are designed to allow smooth movement of snow and slush when you’re rolling, while the wider trailing edge provides greater resistance for braking and steering.

Other companies are making the huge number of pores in the tire’s surface work more effectively.

According to Brad Sherwin of Yokohama Canada, “The enemy of traction is the thin film of water between the tire tread and the ice,” Sherwin explains. “The water is actually causing the slippage. Eliminating much of the water between the ice and snow surfaces and the tread increases its friction with the road itself and hence improves traction.”

Yokohama’s solution is to use what they call “shelled micro-bubbles” that absorb water and break the microscopic water film between the tread and ice and snow surfaces. The micro-bubbles also maintain the rigidity of the tread blocks to create sharp biting edges to deliver confident snow and ice traction.

Goodyear uses a similar design, although it’s referred to as Bubble Blade Technology, on even its entry-level winter tires, like the Nordic from Canadian Tire.

How to choose?

First off, ensure that you’re actually purchasing a proper winter tire. Tires marked with a pictograph of a peaked mountain with a snowflake meet specific snow traction and severe snow condition requirements.

Tires marked “M+S” — or “mud and snow” tires, also known as “all-season” tires — will provide safe all-weather performance, but fall short under severe snow conditions. In addition, M+S tire requirements are guidelines and involve no actual testing to receive the M+S designation, while winter tires must meet strict performance requirements.

If you’re purchasing a new car, some dealers offer winter tire storage during the summer months, and all can include the cost of four winter tires in the purchase price of the vehicle. That’s probably the best way to ensure you’ve got winter tires available for when the weather dictates.

Electronic assists

Recent advancements in electronic driver aids, such as ABS and traction control, don’t provide more traction. They only help prevent you from over-braking or overpowering the available traction of their tires. The only thing you can do to increase traction is to install better tires.

As for two winter tires as opposed to four, Mortimer has done extensive tests with all types of vehicles and comes to one conclusion: don’t put just two winter tires on a vehicle.

“It’s unsafe whether you put them on the drive wheels or the steering wheels,” says Mortimer. “Especially with anti-lock brakes [ABS], traction control, and stability controls, no number of electronics can overcome the laws of physics.”

Again, the reason is to ensure the vehicle predictable to drive. If you put winter tires on the steering wheels, the rear will have a tendency to fishtail or oversteer. If they’re on the rear wheels, the car will understeer.

But one final note on electronic systems: they typically act by applying brake pressure to individual wheels to alter the handling of the vehicle. Traction control reduces wheelspin by applying brakes to the spinning drive wheels — but frequent wheelspin that’s ever-so-present in winter driving can produce overheated brakes and prodigious brake wear.

Add in extremely cold conditions and warped or cracked brake rotors can result. Winter tires improve grip so that your vehicle will rely less on its electronic systems for traction, in turn reducing stress on other components.

If your vehicle is equipped with the blinking yellow light that notifies you of when an electronic safety system is being used, just check out how often the light flashes in slippery conditions. You’ll be amazed.

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