All-wheel drive is extraordinarily popular in the Canadian automobile market. A vast percentage of SUVs and crossovers sold in the Great White North send their power to all four wheels, as the majority of those machines leave the dealership equipped with all-wheel drive (AWD). It makes sense that this is the case, as this great country of ours is locked in a deep freeze from about now until Easter.
In November, every day one doesn’t have to shovel snow is a gift.
In several parts of the country, cold temperatures often precede the white stuff falling from the sky by several weeks. It’s around this time of the year when a lot of Canadians head to their mechanic and get a set of winter tires mounted on their car. It’s also the time of year when more than a few people start saying, usually loudly, that they don’t need winter tires because they have an all-wheel drive vehicle.
Make no mistake on what I am about to say: This. Is. Wrong.
Certainly, there are many die-hard defendants of the notion that AWD precludes the need for winter tires. We expect many of them to appear in the comments of this story. These people are certainly entitled to their opinion but before anyone starts typing furiously on their keyboard, please consider the following arguments.
There is no doubt that all-wheel drive increases the amount of accelerative grip compared to a two-wheel drive machine. Twice the number of tires are actively clawing at the ground, after all. However, it is this author’s opinion (and the opinion of many others) that all-wheel drive, particularly in the winter months, simply gets a car up to crashing speed more quickly.
Why? It has to do with physics. Once up to speed, a car will eventually need to slow down or navigate a turn (or perhaps do both at once). The compounds contained in all-season tires are not designed to be very flexible once ambient air temperatures drop below 7 degrees Celsius, as pretty much the entire nation does during the depths of a long and cold winter.
Mechanics and Molecules
To help back up my argument that AWD vehicles need winter rubber, I gave Ron Margadonna a call. He is the North American Senior Technical Marketing Manager for Michelin, so it’s safe to say the man knows a thing or two about tires and how they’re made.
What sets winter tires apart from their year-round brethren in cold weather can be broken down into two categories: mechanical features and molecular attributes.
“The biggest advantage of winter tires is what we call their glass transition stage,” explained Mr. Margadonna. “This is the temperature point at which a tire goes from an elastic to inelastic stage. The silica in winter tires allow them to have lots of flexibility in extreme cold, meaning they spend more time in direct contact with the pavement, providing more traction and better control.”
For comparison, take a look at the soles of some winter boots in your closet and compare them to a pair of summer flip-flops. Like tires, the sunny weather kicks won’t flex very well if worn in a blizzard and will simply act like a rigid slippery surface compared to the winter footwear. The same principles are at play with what our Michelin expert called the ‘glass transition’ of the tires on your vehicle.
This, then, is the molecular difference between winter and all-season or summer rubber. Non-winter tires simply don’t have the ability to stick to the road in cold temperatures thanks to the material with which they are made. Sure, your all-wheel drive vehicle might get up to speed just fine on all-seasons but when it comes time to stop or turn, regular tires just simply don’t perform to the standard of winter rubber.
“Mobility on the road has three components: accelerating, braking, and cornering,” Mr. Margadonna said. “Modern antilock brakes and traction control systems are great safety cushions, but they are not substitutes for the extra control provided by winter tires.” All wheel drive gets drivers going; winter tires help them turn and stop.
The rubber compounds of which winter tires are made stay flexible at temperatures below 7 degrees Celsius, allowing them to better grip the road. That’s why they’re called winter tires and not snow tires. Their defining characteristics are determined by temperature, not just snow and ice.
This brings us to the other half of the winter tire puzzle – their mechanical features. One might think of tires as simple hoops of rubber but a great deal of engineering goes into them. Winter tires have a traction advantage in cold and wet weather by using technology called sipes.
These sipes are little gaps in the tread blocks of a tire, designed to add extra biting surfaces on the tire’s contact patch. Winter rubber has a high density of sipes which, when combined with their saw-tooth shaped edges, allow for much higher levels of grip on slippery surfaces. “The more edges there are on a tire, the more traction there will be,” Mr. Margadonna explained with confidence.
It is the combination of all these features, the specially designed tread blocks (mechanical) and pliable silica-based construction (molecular) that give winter tires extra traction during the coldest months of the year, regardless of how much snow is on the ground … or how many driven wheels are in play.
Also Read: Top Winter Tires for 2017
No matter what you drive, please be sure to clean all the snow off your vehicle, especially around the windows and defroster vents. If rough weather hits, slow down and match your speed to the conditions. Maintain more distance from the cars around you (yes, this is difficult in Toronto traffic) and feather the brake pedal to slow down before turning.
Bottom line? All-wheel drive will get you going, while a great set of winter tires will help you turn and stop. Together, they make a great combination that’ll keep you and your family safe on the road.