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Still revolving and evolving

Twenty-two years ago, Bridgestone Corp. introduced the ground-breaking Blizzak studless winter tire to the world. Seventeen years ago, the company’s United States subsidiary introduced the Blizzak WS-15 to domestic tire dealers.

Three generations later, Bridgestone Americas Tire Operations LLC announced it will make the Blizzak WS-70 available to tire dealers in July. The company says the dedicated winter tire is superior to its predecessor, the WS-60, in ice, snow, slush and wet braking; ice and snow acceleration; snow, wet and dry handling; and wear (thanks to a deeper tread depth).

The WS-70 performs the same as the WS-60 in ice handling, and rides just as quietly. There is one trade-off: ride comfort.

“The compound is where we’re making the most of the advances in winter tire technology,” says Mark Johnson, manager of product marketing.
 
Technological advances

The evolution of the Blizzak often occurs at the molecular level, according to Johnson. That makes some of the features hard to see with the naked eye.

• Tube Multicell compounding is the key to Blizzak technology. Thousands of microscopic “tubes” or pores are designed to bite into icy surfaces for traction. They are larger in the WS-70 than they are in the WS-60.

(Not all members of the Blizzak family feature Multicell compounding. For example, the Blizzak LM-60 performance winter tire line does not, whereas the Blizzak DM-V1 light truck and SUV tire line does.)

• A proprietary NanoPro-Tech polymer helps prevent the rubber compound, especially the silica filler, from stiffening when the temperature drops.

• New 3D zigzag sipes in the tread blocks are molded vertically at various angles to keep the tread blocks stiff and reduce squirm.

The tire’s tread width also has been optimized, “which creates an elongated footprint” and enhances the WS-70’s snow and slush performance compared to the WS-60, says the company.

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The Blizzak’s tread design also has evolved since 1993. For example, the contact patch is less narrow, which promotes snow and slush performance, according to Phil Pacsi, vice president of consumer marketing for the U.S. and Canada. He says improvements in one area are possible primarily because of advancements in other areas.
 
Size offerings

The WS-70 will be available in 33 T-rated  metric sizes in July. Sixteen of them are 17-inch sizes, ranging from 215/65R17 to 245/45R17. There also are nine 16-inch, six 15-inch and two 18-inch sizes.

Another two sizes are P-metric: P215/55R18 and P225/55R18.

The Blizzak WS-60 will remain available in 19 R-rated sizes.    ■


By the numbers -- Traction/snow treads decrease 7.3%

Preliminary numbers by the Rubber Manufacturers Association (RMA) show a year-to-year decrease in traction and snow tires, defined as tires with “winter, all-terrain and traction treads.”

That’s the first annual decrease in that segment since 2006.

(Because the RMA bases its shipment numbers “solely on the technical characteristics of the tread design,” determining a trend among dedicated winter tire shipments is not possible.)
      
Domestic replacement traction/snow (T/S) treads
(in millions of units; RMA member shipments only)

Year    T/S    % change

2009    8.8    down 7.3%
2008    9.5    up 3.3%
2007    9.2    up 13.6%
2006    8.1    down 3.5%
2005    8.4    up 6.3%

Original equipment traction/snow tread shipments are down nearly 53% since 2005.

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