Winter Tires or All-Season Tires?

In a Pierrefonds arena, Bridgestone, with the help of Transportation Canada, tried to convince journalists that real snow tires offer many advantages over four-season/all-season tires. In Quebec, starting November 15, 2008, all-season tires will have to find themselves another name, as their use in winter will be banned by law.

Winter tires have tread patterns which are specifically designed to bite in the snow and to have grip on ice. They are made from rubber compounds which remain flexible in cold weather, thus enabling the tire to adapt itself to the surface of the pavement.

Tread compounds are designed to work within specific ranges of temperatures. If the tire is used above its rated temperature range, the tread will become softer and will wear rapidly. If the tire is used in temperatures below its rated temperature range, the tire becomes too hard and cannot adapt itself to the surface of the pavement. What’s more, when water freezes and becomes ice, very small irregularities appear on the pavement. If the tire compound is rigid, it will tend to spin over these irregularities. On the other hand, flexible compounds keep their good grip on any kind of surface, offering improved control over any set of conditions. This is why, on snowy or icy surfaces, winter tires give a much better grip then all-season or summer tires.

Braking on ice

Tire grip on ice is crucial to safe winter driving. First of all, it means you will avoid getting stuck. But effective grip is also essential if you want to maintain steering control and ensure that your vehicle can brake effectively. Life-saving technologies, like ABS, electronic stability control and all-wheel drive will not perform well if the tires don’t have any grip on the surface of the pavement.

All-season tires, also called fourseason tires, are designed to perform well under a variety of conditions, including wet and dry pavement; but they don’t perform well in specific winter conditions. Most of the time, when the temperature is cold they don’t adapt well to the surface of the pavement. One can compare all-season tires to sporting shoes, and winter tires to snow boots. One can walk on a snowy and icy sidewalk wearing sports shoes, but it would be a lot easier and safer if one was wearing well-designed snow boots.

According to Transportation Canada, a snow tire is one which offers a traction index equal to or above 110, when compared to the Standardized test

tire ASTM-1136, and can pass the criteria described in the Standardized test method ASTM F-1805-00 for motive traction of a single wheel in a straight line on snow or ice-covered surface. A tire which corresponds to the official definition of a snow tire, as described in paragraph S3 of Transport Canada’s regulations, can bear a pictogram showing a mountain and a snowflake, but this symbol is not mandatory. If the tire maker decides to show the alpine symbol on its snow tire, the profile of the mountain must be at least 15 mm wide and 15 mm high. It must have three peaks, the highest being the one in the middle. On the inside of the mountain, there must be a six-sided snowflake, the height of which must be at least equal to one half the height of the highest peak.

Bridgestone Puts Tires to the Test

Being fairly popular in Quebec, Bridgestone, maker of the famed Blizzak snow tire, has started with the help of Transportation Canada a major campaign to convince consumers of the advantages of really ‘good’ snow tires.

In February 2008, journalists were invited to test similar cars equipped with snow tires or all-season tires, and comparing their braking on the icy surface of a skating rink. The tests were revealing, as one could have predicted.

Patented technologies, like the ‘Multicell’ compound of the tread of the Blizzak, have rendered all-season tires completely outmoded. The Blizzak is also vastly superior to many models carrying the proverbial snowflake logo. Starting for this winter, Bridgestone released a new Blizzak, the WS 60, built along UNI-T and NanoPro-Tech technologies, which work together to maintain water outside the contact patch of the tire while improving the flexibility of the tread, which results in a much better grip on snow and ice. The compound is composed of thousands of microscopic pores, which make the tire look sort of like Swiss cheese. When the tire is affected by wear, new pores are continually exposed, creating thousands of suction cups which grip the road.

While having a ‘biting’ effect, the pores also help to evacuate the thin film of water which is often present over icy pavements. Yokohama and Michelin also have tricks of their own to evacuate water and to augment the grip of the tread on the pavement, greatly reducing the tendency to aquaplane. The result is improved handling, greater manoeuvrability and top-notch braking. In the case of the Blizzak, new pores are continually exposed, which means the tire will keep its ‘brand new’ quality for all its useful life.