GAINING TRACTION

Just as weight restriction signs are posted in the Upper Peninsula during spring break-up, eleven European countries and three Canadian provinces post signs in the fall warning drivers that they must equip their cars with winter tires or risk a ticket.

By Bryon Ennis.

My 2010, all-wheel drive SUV usually performed well on snow-covered Upper Peninsula roads, and I credited this normally safe, sufficient traction to the four all-weather tires that came on the vehicle. However, I experienced two hair-raising episodes when, of its own accord and totally without warning, my SUV suddenly broke from its tracking and performed a 360-degree pirouette on packed, refrozen snow. Luckily, in both instances no cars were approaching from the opposite direction. Because this SUV normally performed well enough, I wrote these scares off as my fault for “probably” driving too fast for conditions. However, when I later bought a lumbering, full-sized family van as my long-distance touring car, I became concerned during the first November snow days that I could hardly execute a cautious turn without some sideward slide, and stopping within a predictable distance was always a crapshoot, despite the fact that this car also came equipped with popular name-brand all-weather tires.
I soon became convinced that the frequent poor traction when starting, turning and stopping on Upper Peninsula snow was too great a risk for my family, but I also felt I couldn’t trade in this car for a different model. What a financial loss it would be. Besides, I really enjoyed the comfort and the room of this big van in warmer weather, and it even got good gas mileage. I had to do something, even if it meant buying noisy snow chains or studded tires. Then one day, when I was taking my family van in for maintenance, I noticed an advertisement on the car dealer door stating that Dedicated Winter Tires (don’t call them snow tires) Do Make a Difference. I certainly had my doubts. Could a simple thing like a different tread pattern really tame the behavior of my behemoth on snow?
After much internal consternation on my part, external assurances from the mechanics and discussions with the Secretary of the Treasury (my wife), I decided to blow a wad of cash and purchase four top-of-the-line dedicated winter tires. I had to put four of these winter tires on my vehicle, even though it was front wheel drive. The mechanics explained that starting traction was only part of the function of dedicated winter tires. Braking and turning traction were even more important, and for this, four winter tires were required.
As I drove home after the tire change, I cautiously put the car and my new winter tires through a trial test. First, I found a lightly traveled, plowed road with a skim of packed snow covering it. “OK, let’s see how she accelerates… Good, good, no slip at all.” Next, a rather tight curve. “Fine, no sideways slide.” Now for the ultimate stopping test: “Dynamite the brakes!” I heard practically none of that awful vibration from the automatic braking system that used to indicate the tires were sliding. In the next few days and weeks, I became convinced that my new dedicated winter tires really did make a difference. But how could they work so well without even having studs?
I found several major differences between all-weather tires and dedicated winter tires that provide exceptional traction not only on snow but on ice as well. Each of a winter tire’s unique characteristics is essential to this amazingly good traction, so it is impossible to say which is the most important. To start with, we must consider the pliability of the rubber. Dedicated winter tires have very soft rubber that does harden as the temperatures drop, even during 20- or 30–below-zero Upper Peninsula nights. All-weather tires cannot contain such a soft rubber and still hold up during the warm summer months, especially in super hot places like Phoenix, Arizona. Dedicated winter tires would become so soft under Arizona temperatures that they would be unstable and dangerous (so you shouldn’t try to drive across the county in summer with winter tires).
Dedicated winter tires are also equipped with thousands of almost microscopic slits in the tread, which the tire manufacturers call “sipes.” If you look closely at all-weather tires, you can see a small number of sipes, but nowhere near the thousands that exist on dedicated winter tires. These thousands of slits open and close as the tire spins, and as they contact the road, they allow the tire to more closely match the microscopic irregularities of ice or snow, eliminating tiny air spaces between the tire and the elements. This helps your car grip the road and gain far better traction.
A third important difference between all-weather tires and dedicated winter tires is the depth and width of spaces between the “blocks” that make up the tread. On a typical all-weather tire, the spaces between tread blocks are narrow and shallower than on a winter tire. Since winter tires have deeper spaces between tread blocks, the blocks’ functional height is greater, helping the tire take bigger bites of loose snow. Many drivers are surprised to learn that the larger spaces between the blocks of tread allows soft snow to stick in the those spaces while that section of the tire is contacting the road. This is desirable because tire scientists have found that snow-on-snow has a greater friction component than rubber on snow, meaning the tire “catches” the loose snow and uses it to gain an even better grip on the packed surface.
Some countries consider winter tires so important for safety of drivers, passengers and passersby that they have laws requiring winter tires. Just as weight restriction signs are posted in the Upper Peninsula during spring break-up, so eleven European countries and three Canadian provinces put up signs in the fall warning drivers that they must equip their cars with winter tires or risk a ticket. Though it is said the police don’t go around inspecting people’s tires, if a driver happens to be at fault in an accident or even the cause of a traffic tie-up, they are subject to an additional fine, and their insurance may not cover damage.
One drawback to dedicated winter tires is that they wear faster on dry pavement than all-weather or warm-weather tires, so it is important to remove them from your car when the chance of snow is small (hmm, when is that in the Upper Peninsula?). After that first winter, I bought four steel rims for my winter tires. Steel rims reduce the risk of wheel damage, both because they handle the winter road salt and sand better than aluminum and because putting new tires on a rim can weaken the sidewall and bead—especially on a “softer” metal like aluminum. Having a set of steel rims is also more convenient: now, I can just exchange one set of tires and rims for the other, and neither set needs to be rebalanced when they get changed.
Drivers might question whether the added expense of an additional set of tires and wheels is really worth the cost. Safety-wise, there is no question in my mind that winter tires are worth the price for greater peace of mind. And you can consider the wear factor on two sets of tires like this: each set is used for half the year, so each set lasts twice as long. I have been using my dedicated winter tires for three years now, and my mechanic says they definitely have enough tread to carry me through the coming winter. For the sake of your safety—and your family’s safety—this is one investment you’ll want to make this holiday season.

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