December 7, 2005

Update on winter tire technology
by Jim Kerr

It rained last night, and now the temperature is below zero. You know what that means: ice everywhere! The insurance companies are busy, the body shops are busy and so are all the tire installers.

Winter tires are perhaps the cheapest safety insurance you can buy for yourself and your family. A higher percentage of Quebec drivers install winter tires than those in the rest of Canada, but winter tire use is increasing across the country as more drivers become aware of the technology that gives them a significant advantage over summer and all season tires in cold weather.

Bridgestone Blizzak tires were the popular choice when winter tires specifically designed for icy roads first hit the market, and winter tire technology has undergone tremendous improvements since the time the first Blizzak tire was introduced. Bridgestone's Bill Vandewater, Consumer Products Manager, Sales Engineering talked to me about the qualities of the new Blizzak REVO 1 tire design. The Revo 1 uses tube multicell compound, long-link carbon black and 3D sipes to provide durability, handling and traction.

Tube multicell compound is one of those secret ingredients in the REVO 1 tire. A chemical compound is mixed with the rubber and during the hot curing process, this compound forms a gas, creating a small tubular void in the rubber. Rubber has good grip on ice if it can contact it, but a water film generated by the pressure of the tire on the surface makes the ice extremely slippery. The water can enter the tubular voids, allowing the rubber to make contact with the ice, giving the tire traction.

An "environmentally friendly bite particle" is bonded to the side of each tubular void and acts like a microscopic stud to scratch the surface on hard ice, for more bite. Rubber compounds are highly guarded secrets and even Vandewater wasn't privy to exactly what the bite particles or multicell compound was made of.

Long Link carbon black provides durability to the tire. Carbon black gives the tire its colour, but it also wears well. Normal tire wear occurs as microscopic particles are torn from the tire surface. By using this custom designed carbon black long linked molecular chain, the surface is less susceptible to tearing, giving the tire longer tire life.

3D sipes are a REVO 1 feature to improve handling on dry pavement. Sipes are small cuts in the tire tread that provide grip on snow. Many believe they provide grip on ice, but it is the rubber compound that grips ice. The sipe edges bite into snow, just as the bigger tread blocks do. The 3D design on the REVO 1 has an angled step about half the depth of the sipe that "locks" when the tread block tries to distort during braking, acceleration or cornering. The stiffer tread block improves handling response.

Flexible rubber compounds are a key winter tire feature. The tread must remain soft at low temperatures so it can conform to the surface of the slippery road. The first generation of Blizzak tires used a winter compound for the outer half of the tread depth and an all season compound for the bottom half. The current design has the same cold weather flexibility compound all the way through but the tubular multicells are only in approximately the top 55% of the tread surface. Eliminating the multicells from the bottom part of the tread improves handling by creating a stiffer tread block.

Vandewater tells me the best time to install new winter tires is in the Fall, so you can take advantage during the winter of the snow traction provided by the full tread depth. As snow disappears in the spring, your worn tires will still have the flexible tread compound to grip the ice. The REVO 1 has four wear indicators that show as bands across the outer tread groove when the tire is about 55% worn. They are still good for ice or pavement, but snow traction would benefit from new tires.

The REVO 1 is available in directional and non-directional tread patterns. Lower profile tires use directional patterns to help remove deep water better, while narrower tires work fine with non-directional patterns.

Finally, I asked Vandewater what makes the Blizzak REVO 1 better than other winter tires on the market. He says tire technology leapfrogs itself all the time. Improvements made by other manufacturers are studied and incorporated into the latest designs. The REVO 1 is one of the newest winter tires on the market, so it incorporates the best technology from everything that has been on the road before.

Jim Kerr is a master automotive mechanic and teaches automotive technology. He has been writing automotive articles for fifteen years for newspapers and magazines in Canada and the United States, and is a member of the Automotive Journalist's Association of Canada (AJAC).

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