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Best new winter tires

Winter driving is not just about driving on snow, it is about grip under all road and atmospheric conditions.

Winter driving is not just about driving on snow, it is about grip under all road and atmospheric conditions.

Here in the GTA that means mostly cold dry pavement. As temperatures drop below 6C to 7C, your all-season tires start to lose grip, while winter tires gain grip.

What’s not to like about more grip? It means more of a safety margin for you and your passengers.

The four main physical problems of winter driving your tires must endure are cold, wet, snow and ice. Any one of these circumstances is cause for concern. When any two or more combine, you can expect a very long commute home.

Tire companies have not been idle or resting on their product laurels. They continue to upgrade their products using the latest science and this year we have a bumper crop of new winter tires.

Following is a summary of each of their highs and lows:



YOKOHAMA ICE GUARD IG20/

GEOLANDER I/T GO72

We’ve all seen the sign Slippery When Wet with the pictograph of the skidding car. Just how much wet does it need to create slippery?

That was the key question when Yokohama engineers set out to create their latest generation of winter tire.

But before hitting the test labs, the engineers hit the books, the StatsCan books on numbers of traffic collisions involving fatalities from 1989 to 1997. That graph had a nice, steady downward trend in fatalities, but the number of collisions on slippery surfaces stayed steady. through the same period.

Short version of the collision analysis was that cars’ newer safety features were saving lives, but cars were still slipping around at the same rate as always.

But what about all of our electronic nannies and saviours: all-wheel drive, anti-lock braking and the pièce de résistance, stability management?

The bottom line: these systems cannot create traction; they can only maximize the traction that is available at the tire’s contact patch.

The problem in winter driving is that there is almost always a film of water between the tire and the snow or ice.

The film of water is created by the weight of the car pushing on and compressing the snow or ice. The resultant film acts as a lubricant.

The next issue to solve was at what temperature was this phenomenon at its worst. There are two temperature ranges where this mini-aquaplaning occurs.

The first is when the temperature is between -6C to 0C. Here conditions are perfect for pressure from the tire to create water. The second situation is when ambient temperatures are above freezing and road ice is melting on its own.

The answer: a water-absorbing tire compound will work best. Multicell compounds have been around for a few years. These are compounds with little cavities in the rubber tread. As the tire rotated, new cavities were exposed, water could temporarily retreat into the hole and better rubber to road contact was possible.

Both the Bridgestone Blizzak and last year’s Yokohama Ice Guard IG10 used that principle.

The problem is that all that porosity in the rubber made for a very sloppy drive on pavement.

The rubber was just not rigid enough to make emergency manoeuvres with confidence. The Bridgestone is only multicelled for the first 55 per cent of its tread life.

Yokohama looked to solve all of these problems with its new Ice Guard IG20, and it has succeeded, big time. The first brainwave was to use hard, hollow resin micro bubbles in the tread.

Dispersed like little beads throughout the tread, the bubbles allow the tire to remain rigid for more assuring grip in corners and under braking.

When the come in contact with the road, they pop open and suck in the water much like a suction cup. It is sort of like popping the bubbles in bubble wrap.

These little guys are typically 0.25 mm, which is very small to you and I, but looks like a huge cave to a 10-micron-thick water droplet.

After determining just how many of these resin pop toys could be used in a tire, Yoko went for the hat trick of water absorption via carbon flakes.

These flakes were shaped into heavily layered “beehives” measuring a giant 0.5mm. Capillary action draws road water up into these layers. As the tire rotates, water is expelled.

In total the average IG20 tire has about 2.5 billion of these hard micro bubbles and 1 billion carbon deposits.

To top all this, the Yoko IG20’s tread pattern uses other elements to help manage winter roads. Four wide, straight grooves around the circumference of the tire help evacuate snow and water and contribute to straight-line stability.

Slush grooves run out to the shoulder of the tires to help drain wet snow and slush.

Driving pre-production IG20s last winter proved to me that the lab theory translated well where the rubber meets the ice.

In back-to-back comparisons with the new Ice Guard IG20, Goodyear UltraGrip Ice, Bridgestone Blizzak WS-50 and the Michelin Alpin, the new Ice Guard aced every test.

On an outdoor track laid out with snow, ice, slop and hard-packed snow, the IG20 was fastest in acceleration, quickest in stopping and highest in lateral grip. And it had a decent ride as well.

The new Yokohama is available in 51 sizes, ranging from 13-to-18 inch diameters. Aspect ratios run from 80 down to 40. Speed ratings are between Q and T; alas, nothing extends into the H-speed range for sports sedans.

The GO72 is the SUV/pickup truck version of this tire. It comes in 23 sizes in diameters from 15 to 17 inches and aspect ratios of 75 down to 65.



BRIDGESTONE BLIZZAK WS-60

Bridgestone has not been resting on its laurels with its Blizzak, even though it has sold 100 million of these “Winterbiter” tires worldwide since their introduction.

This year, the company has a new generation, the Blizzak WS-60. The research in the lab and on computer simulations solved a basic contradiction in winter tire design that has been with us since Day 1.

A winter tire with a high void area works best on snow. A tire with a low void area works best on ice. Void area is the open area in a tire’s tread. Grooves and sipes that are open are considered void area.

(Sipes are thread-like slits in the tread that help evacuate water for better wet traction and act as biting edges in snow.)

The new WS-60 uses a new proprietary Cis Butadiene rubber compound. This compound bonds better with silica to enhance traction in wet and snow. In fact, it increased snow traction so much that Bridgestone was able to reduce the void area of the tire by huge percentages.

Rubber with a high Cis content has better low-temperature flex characteristics and is more abrasive resistant for longer tread life. It also stands up better to flex fatigue for longer heat-cycle life.

The centre of the tread area has a 37 per cent greater contact patch , compared to the previous generation WS-50. In the shoulder area, the increase is 84 per cent, while sipe edge density is up by 21 per cent.

Within this new rubber compound, Bridgestone went from tiny air bubbles as in its previous Blizzaks to tine worm-like tubes.

These tubes are fully 50 per cent larger than the pockets in the older generation of tires.

When the tubes are exposed, they give water a place to hide while the tread grips. The water is then expelled as the tire rotates.

To provide extra grip, the WS-60 now has an abrasive material added to the tread rubber. These little bits of grit (Bridgestone refuses to say what they are made of) are quite the little grabbers on ice.

You can actually see small scrapes on the ice where the tire has passed. To ensure that the grit bits don’t fall out with the first forceful tire spin, they are chemically bonded into the rubber with a special coating.

All of this techno wizardry is topped off with a directional tread pattern, angled grooves and long-lasting sipes.

The Blizzak WS-60 has the multicell rubber on the first 55 per cent of its tread. Below that, the tire reverts to a normal winter tread compound. These new winter boots are available in 38 sizes in diameters from 14 to 17 inches and aspect ratios of 70 down to 45.

All sizes are R-speed rated (good for up to 170 km/h).

Bridgestone makes other winter tires for cars requiring a higher speed rating.



MICHELIN PRIMACY ALPIN PA3/

PILOT ALPIN PA3

Part of the name is old and part is new. PA3 is the part that matters in this latest effort from Michelin. These tires will gradually replace the firm’s Alpin predecessors.

The Primacy line is the sedan tire and the Pilot line is Michelin’s highest-performance group.

Primacy comes in eight sizes this year; all are H rated. By recompounding the rubber and then reworking the tread pattern, Michelin has improved this tire’s lateral grip by a full 10 per cent over the previous Alpin. That gain is so significant that this tire can’t be used with any previous Alpin.

There is also a 10 per cent increase in acceleration on snow. This is accomplished by increasing sipe density and block edges at the tire shoulder.

You also get much better grip on wet cold pavement. And, to top it off, the Primacy uses sunflower oil as part of its compounding, saving some precious natural resources.

Similar improvement numbers come on the big V-rated Pilot Alpin PA3. This tire is asymmetrical unlike its predecessor. It features variable sipe thickness – wider ones on the inside for better snow grip, narrower ones on the outside shoulders for better cornering grip.

The result is a claimed 10 per cent better handling on snow and 5 per cent better handling in the dry. These are solid gains on a tire that already had prodigious grip.

Wet-road handling showed improvements of 7 per cent more handling in transitional manoeuvres like direction changes and 10 per cent better grip in steady-state cornering.

Again, this tire cannot be mixed with any other winter tire, Michelin or otherwise.

Michelin is expected to hold the pricing line on both these products. No increase in price for increased grip. I like that.



GOODYEAR ULTRAGRIP

PERFORMANCE

This new, European-inspired winter tire features a more open tread block design than one would expect on such a boot.

The wide gaps between blocks indicate it should do well in deep snow. This is a new direction for Goodyear, where deep snow grip has not always been Job 1.

The multiple long sipes provide ice grip, interlocking and supporting one another under side load. Goodyear calls this TredLock and says the shoulder rubber can generate lots of cornering hold.

Rubber technology has been improved from the firm’s previous winter tires.

An asymmetric tread pattern provides the different types of tread blocks needed for all cornering situations. Fitments are available in nine sizes for most European sports sedans that run 16-to-18-inch-diameter wheels.

For ultra sports sedans, consider the Eagle UltraGrip line, unchanged for 2007.



GOODYEAR ULTRAGRIP SUV

This is Goodyear’s first real winter tire aimed at the SUV/crossover market. Its V-shaped tread pattern closely mimics the company’s most aggressive winter tires for cars.

Goodyear has done its homework: the shoulder blocks – the highest-stressed parts of SUV tires – have very wide, interlocking blocks. This should keep vehicle weight from rubbing off those all-important shoulder edges. The tire’s offset shoulder design helps provide good off-road and snow performance.

This product serves up many interlocking, angled sipes for cornering grip on ice.

Its interlocking tread block system gives enhanced dry-weather handling. The directional tread pattern and wide circumferential grooves help evacuate water.

UltraGrip SUV will be available initially in eight sizes for 16- and 17-inch rims.

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