Your guide to winter tires

Winter tires ensure proper traction action when the rubber hits the snow – or ice

Nov 07, 2008

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Special to The Star

There will be snow. There will be ice and there will be cold. These are upcoming certainties and the time to prepare is now.

Would you wear summer sneakers and expect traction on ice? Neither does your car. Try running on ice in your sneakers. After you have picked yourself up, put heavy socks over the outside of your sneakers – suddenly you have traction.

Traction in the cold is difficult to find. Traction loss on bare pavement for a typical all-season tire sold in Canada starts at about 7C. Anything colder and traction losses mount rapidly.

So winter tires are the answer if you enjoy stopping in a straight line after Jack Frost visits.

And that would be four winter tires, not two, no matter what kind of drive system your car may use. Try running down the street with one winter boot and one summer shoe if you need a graphic experience to reinforce the idea that a car should have balanced traction.

Winter tires and the new category of all-weather tires are made to grip in cold conditions. Some are better at snow while some are better at ice, but even the worst, cheapest winter tire will have better grip than an all-season tire when temperatures drop below freezing.

Rubber technology in tires marches forward with every season change. It is important to every tire company to stay on top of consumer ratings.

Sales volumes increase every year, and especially this year because a new law in Quebec mandates winter tires must be installed on every vehicle by Dec. 15. Count on a winter tire shortage.

In fact, the potential shortage has prompted a rash of thefts of new winter tires and wheels from cars in the area north of Montreal. With the diversion of tires going to Quebec, some sizes will be sold out before Santa flies to town.

Already, some common sizes are listed as back-ordered. Back-ordered is corporate speak for you'll get them in July 2009.

Winter tires are manufactured in the opposite season. Right now, tire plants are producing next summer's rubber. Smart dealers ordered and took delivery of winter tires months ago.

There is one significant new tire on the market for this season: the Michelin X-Ice Xi2

Michelin has finally created a tire that uses air spaces in the rubber to act as little suction devices to improve ice grip. Michelin calls its design "micro-pump technology." Bridgestone pioneered this kind of grip enhancement with its Blizzak brand, and Yokohama continued in this direction with the IG20 Ice Guard.

Michelin has not entirely gone the route of the other two, which randomly have air pockets throughout the tread rubber. Michelin has added little tubes in a well-planned mixture through the tires' heavily siped pattern. The result is amazing stopping grip on ice superior to the X-Ice.

Ice is slippery because when we step on it or a car drives on it, the weight causes a thin film of water to be released. The water acts as a lubricant to increase the slip and slide of whatever caused the pressure.

Michelin combines the round micro-pumps with a new tread block heavily siped and made of a new rubber compound called FleX-Ice technology into its tread design.

It works simply. The leading edge of the tread block pushes most of the water out of the way in to the bigger grooves; the micro pumps absorb the remaining water; the sipes have better grip on the now-mostly-dry ice surface and, as the car moves forward, the pumps expel the water to be ready for the next contact.

It is an elegant solution to ice grip. On dry roads, the tire retains enough firmness in the tread to resist that dreaded "winter tire squirm."

The X-Ice Xi2 gets the "Green X" rating from Michelin, which means the rubber it uses is part of a line of tires that has lower rolling resistance and lower fuel consumption compared to a regular rubber. Michelin claims that if the world's vehicles were equipped with Green X tires, carbon dioxide emissions would be cut by 72.6 million tonnes.

Michelin claims its new tire will last 75 per cent longer than its main rival. The unnamed rival, I suspect, is the Bridgestone Blizzak. And that vast difference in wear rate would be based on the fact the Blizzak is a multicell compound for only 55 per cent of its tread depth. The remaining 45 per cent of the tire is a standard winter compound.

The Michelin X-Ice Xi2 is available in 42 sizes in rim diameters from 13 to 18 inches and aspect ratios of 70 down to 45.

John Mahler answers Wheels readers' questions in his regular Tire Talk column. He can be reached at thetireguy_1@hotmail.com

Toronto Star