RIGHT SET OF TIRES

WHY THE RIGHT SET OF TIRES IS MORE IMPORTANT THAN YOU THINK.

BY ERIC TINGWALL – SENIOR EDITOR AT AUTOMOBILE MAGAZINE – NOVEMBER 2012

I once met a guy who seemed to think quite highly of himself for surviving three Michigan winters in a Pontiac G8 shod with the stock summer tires.  His expert advice for anyone attempting such idiocy? “Never stop at a red light in the snow. You’ll never get going again.” Six feet under, in Westminster Abbey, Charles Darwin smiled. If your car can’t find the traction to get to 10 mph, your game plan probably shouldn’t include running red lights.

We’ve long preached the importance of the right tires for the season but have rarely supported that message with anything more than anecdotes that run against our suicidal G8 driver’s advice. The right tires allow you to accelerate more quickly, change direction faster, and, most important, stop shorter. And when they’re the difference between hitting something and avoiding it, the right tires save sheet metal, money, and, potentially, lives.

This tire talk isn’t just for folks who live in wintry climes, either. There’s plenty of incentive to trade out your all-seasons even in Southern states. To prove that point, we fit our long-term Dodge Charger with all-season, winter, and summer tires and performed panic-stop tests on both a snow-packed surface and a warm, dry road. This isn’t an exhaustive, scientific test, but rather a real-world illustration of the consequences of using the wrong tire.

We sought top-performing tires in each category, and with Tire Rack providing recommendations, we settled on Pirelli PZero summer tires and Continental ExtremeContact DWS all-seasons. In a nod to practicality, our winter selection — the Bridgestone Blizzak DM-V1 — was narrower than the stock tire and rode on a smaller wheel. Downsizing the rim saves money, and a smaller tread width improves performance in the snow. “A narrower tire cuts through the snow and down to the pavement, rather than riding on top like a ski,” says Tire Rack product information specialist Woody Rogers.

With the Blizzaks mounted, the Pirellis shoved in the back of the Charger, and the Continentals following behind in a chase vehicle, we outran spring’s imminent arrival last March to test on the packed-and-groomed, snow-covered surface of Michigan Technological University’s Keweenaw Research Center. It’s no surprise that from 30 mph the Charger stopped the quickest with the winter tires, but the data also reveal how high the stakes are without them. The stopping distance of the all-season Continentals is nearly double the distance of the Blizzaks. Even more indicative of the possible consequences: at the point where the winter tires stopped, the Charger is still traveling 20 mph with the all-season tires.

With summer tires mounted, we modified that Pontiac G8 driver’s advice — don’t bother trying to stop, because you probably won’t. After 74 feet — the stopping distance of the Charger on winter tires — the Pirelli-equipped car has shed just 4 mph and will slide for another 258 feet before coming to rest. Scarier still, the overworked antilock braking system experiences critical brake fade well before the car stops. The pedal drops to the floor and braking force plummets, turning the driver into a passenger as the car sails across the slick surface.

Several months later and with dry pavement undertire, we ran the same test, but this time from 70 mph. Although the distance gap narrows with more traction, there is still a distinct difference in stopping distances. The PZero summer tires record the shortest distance at 149 feet, and the winter tires need the most room to stop — an extra 56 feet. The all-season Continentals are no slouch at 167 feet, but there’s no question that they’re compromised. Using the summer tires could be the difference between stopping before a collision takes place and hitting something at 22 mph.

The right tire for the conditions has serious implications for braking distance. You can try to save money by using one set of tires year-round; you can ignore the fact that your new car arrived on summer rubber in a four-seasons region; you can settle for the decent performance of all-season tires; but in a panic-stop situation, the laws of physics don’t care about any of that. They only care what tires you’re driving on at that moment.

Read more: http://www.automobilemag.com/features/news/1211_rubber_matter_tires_test/

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