With the sun shining and temperatures warming up during the day, it feels
like we should be simply enjoying the fall weather, but it is also time to
get around to those fall chores like raking the leaves and cleaning the
flower beds. Getting your vehicle ready for winter is one of those necessary
tasks, but we often overlook it until something goes wrong.
Spending a few minutes checking fluid levels, belts, lights and cleaning
battery connections goes a long way to preventing trouble down the road.
Changing to winter tires is also an important task that more and more
Canadians are performing. Starting in 2008, Quebec even made it mandatory
for drivers to have winter tires on their vehicles from November 15 through
April 15 of each year. J. Konick, Head of a Quebec task force on road
safety, says about 10 per cent of Quebec drivers haven't been using winter
tires, but they are involved in 38 per cent of winter accidents on the road.
Most drivers think winter tires are built for traction on snow and ice, and
they are correct, but Pirelli research shows that winter tires are really
tires for cold weather, even when there is no snow and ice. As temperatures
drop, tire compounds become stiffer and don't conform to road surfaces as
well. Acceleration, braking and cornering ability all decrease. Summer
performance tires are affected the most, but all season tires also become
less pliable as temperatures drop. Winter tires use different compounds that
remain much more flexible in cold weather and that is part of what gives
them superior traction when temperatures drop.
Instead of waiting for that first snowfall, Pirelli suggests that seven
degrees C is the temperature where drivers should be switching to winter
tires. Above that temperature, the tread compound of a winter tire can wear
quickly, although they still meet all tire safety requirements and can be
driven on the highway at normal speed. Below that temperature, the winter
tires quickly begin to outperform other types of tires, providing the
traction and safety drivers want on cold road surfaces.
Four areas of winter tire design help provide traction. Tread design, such
as grooves, block layout and pattern provide about 50% of the traction on
fresh snow, but this quickly drops off as the snow packs. By the time it
becomes icy snow, the tread design helps very little with traction. The
tread compound provides about 40% of the tire traction and this remains
remarkably consistent in most road conditions, from fresh snow to icy packed
snow. The compound benefits only begin to decrease when driving on black ice
(ice on the road you can't see), where the compound may only provide about
10 per cent of the traction.
Sipes, those little cuts you see on the surface of the tread, can provide up
to about 40 per cent of the traction on packed and icy snow. They work in
two ways. First, they have many small edges that can grip the slick road
surface. Second, water between the tire tread and the ice surface can be
picked up in the sipes so that the tire isn't "floating" on the ice. Wet ice
has to be the lowest traction surface we drive on! Winter tire engineers
concentrate on providing a tire design and compound that will remove water
from between the tread and the road.
Finally, there are studs. Studs are metal pins inserted into the tread block
that dig into the ice for additional traction. Studs work well on black ice,
but provide little benefit on snow. As temperatures drop and the ice becomes
harder, especially below minus 20, the studs will have less effect even on
ice. Studs are also noisy, clicking along the road, and wear the road
surface. Many areas of the country prohibit studded tires except at certain
times or areas.
I asked a tire engineer with one of the tire companies what the best winter
tire on the market would be. He answered me honestly, saying that probably
the newest tire on the market would likely be the best. He based this on the
rapid changes in rubber and tire technology. Newer tires simply have newer
technology, but no matter what you choose, any winter-specific tire will
outperform even the best all-season tires when temperatures drop.
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