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Snow Patrol: All-Wheel Drive Won't Help Without Winter-Friendly Tires

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winter, AWD, tires
A winter’s storm descended on New England last Saturday, and there was the big annual benefit for my radio station that night, 20 miles away—I couldn’t not go. Actually, I wasn’t that worried, because I had a perfect test car—a 2014 BMW 320i with X Drive all-wheel drive and dynamic stability control (DSC).

The 320i bristled with the latest technology, ABS, DSC, AWD. But performance tires were its Achilles Heel in last week's storm. (Jim Motavalli photo)The problem is that over confidence can get you into a trouble. It’s a common concern with SUV drivers, who don’t really get that having all four wheels driven is great for snow, but not nearly as much help on ice. I had a perfect storm out there—driven snow, but plenty of ice, too.

And as it happened, although I drove very slowly and carefully, I slipped and slid all over the place, both on local streets and on I-95. There were times when I was going sideways, and there were stop signs that I just couldn’t obey. I was white-knuckled a lot of the way, but had gone too far to just turn back.

The ride back, with an extra inch of snow on the ground, was even worse. I hit patches of deeper snow near the exits that just sent the car into a spin—luckily, I didn’t make it worse by hitting the brakes, and eventually got it pointed forward again.

Home safely—thank you St. Christopher, patron saint of travelers!—my first question was, “What just happened?” It wasn’t immediately clear. The AWD was working, and I had the DSC switched on. And then it dawned on me—the tires. The 320i as tested had the $1,000 sport package, and came with the optional mixed-size Bridgestone Potenza performance tires.

The culprit: A set of performance rubber. That's great for zero to 60 times, bad for snow and ice. (Jim Motavalli show)“They would be the culprit,” said BMW spokesman Dave Buchko. “You have just experienced why having the right tires for the conditions is so important. All-seasons would have been better but proper snow tires would have been even better.” I noticed these guys boasting of their 3-Series X Drive cars' performance in snow, and they're all wearing all-season tires.

Edmunds informs us, “AWD can only help a vehicle accelerate or keep moving: It can’t help you go around a snow-covered turn, much less stop at an icy intersection. ESC can prevent a spinout, but it can’t clear ice from the roads or give your tires more traction. Don't let these lull you into overestimating the available traction.” And with performance tires, on ice, traction is a rare commodity.

Talking to Dave led me to Mark Cox, director of the Bridgestone Winter Driving School in Steamboat Springs, Colorado. “It’s all about the tires,” he said. “It doesn’t matter what kind of car you have, or the technology on board—AWD, DSC, antilock brakes—the key thing is your connection to the road. There are four contact points about the size of your hands. The technology can’t manufacture traction or overcome the laws of physics.”
 
Most cars come with all-season tires, which Cox derides as “in many ways a no-season tire.” It's unfortunately true that all-season tires are designed with both winter and summer performance in mind, but they don't offer maximum performance in either season. The latest winter tires are designed to stay flexible in cold weather, which increases traction.
 Making the snow fly at the Bridgestone Winter Driving School. (Bridgestone photo)If you live in the snowbelt, I’m afraid you’re on the hook here. I know it’s a drag to keep two sets of tires--they're expensive!--and switch between them everytime the leaves fall, but that’s unfortunately the best thing to do. And don’t let your tires wear down too much, because worn winter rubber isn’t any better than all-season rubber.
 
Of course, the nut behind the wheel--you--has to make the right decisions--it's not just about tires. Cox gave me some good snow and ice driving tips, which perfectly complement the masterful advice compiled by our very own Tom and Ray.
  • Keep Your Distance. It takes four to 10 times as long to stop in winter, so you need to look further down the road to identify problems and respond appropriately to avoid them.
  • Get a Grip. Use all the grip you have available, meaning one input at a time. Brake only when traveling in a straight line. Turn the steering wheel only when you’re completely off the brake. And accelerate when you’re through the turn.
  • Watch the Other Guys. Adjust your speed to the conditions, and consider the other drivers. The capabilities of the car next to you can be 50 to 70 percent different.
  • Freeze Out. Road surfaces are at their most slippery as temperatures approach freezing. That’s because there’s more free water on the surface, which lubricates the ice and snow. As it gets colder, there’s no water on the surface, so more traction is available.
  • Contents Under Pressure. For every 10 degrees of temperature drop, you lose a pound of tire pressure. And low-pressure tires are subject to damage or failure. Check your tires monthly (listen to President Obama!), particularly in the fall.
And just because it has a certain hypnotic quality, here's a video taken through the window of a 2011 BMW 3-Series with X Drive, during a winter storm. This is Buffalo, where they take winter seriously, and the BMW seems to be handling it well.

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winter, AWD, tires

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