Your car or truck was most likely delivered with all-season tires. If
you’ve had them on the vehicle for two or three years, they’re
probably inadequate for winter. Even brand new, an all-season tire will
not approach the performance of a dedicated snow tire in slush or on ice.
Here’s what you need to know before you go out to buy winter tires:
Tread depth
The minimum tread depth you need at the start of winter is 6/32” (
4.8 millimeter).
For an approximate idea, take a conventional Canadian quarter and stick
the caribou, nose first, into the deepest part of the tread. The tip of
the nose should be buried; if not, the tread depth is inadequate to see
you through the winter.
Tire pressure
Tire pressure is critical to handling, especially for vehicles
equipped with low profile tires. Check pressures once a month, except in very cold weather when tire
valves can freeze. It’s important to adjust tire pressure in the
autumn, because the drop in temperature causes the air pressure in tires
to go down significantly: tire pressure is reduced by 1.7 PSI (0.12 bar)
for every drop of 10
If you don’t know what pressure to set the
tires to, look for a yellow label posted by the manufacturer in the door
opening, glove compartment or console bin; the owner's manual also
contains this information. And don’t forget to check
the spare. The small space-saver spare in the trunk of most cars has to
be filled to about twice the pressure of the other tires; it probably
has not been checked since the day your vehicle left the factory!
Where to place winter tires
Winter tires on most vehicles belong on all four wheels. Putting two
winter tires on a front-wheel drive vehicle creates an unstable,
unbalanced vehicle. The same holds for all-wheel drive vehicles.
Rear-wheel drive vehicles need winter tires at the front as well for maximum
braking performance and steering ability in winter conditions. If you own
a vehicle and are not prepared to pay the additional cost of four
winter tires, consider purchasing all-season tires for year-round use.
Two winter tires can be installed on the rear wheels of two-wheel
drive pickup trucks, but it is preferable to mount them on all four
wheels.
Winter vs all-season
An all-season tire is adequate for mild winter conditions prevalent
in southern Ontario, particularly when the tire is new. The best
indicator for the vehicle owner is past experience. If you plan to keep
the vehicle more than three years, the purchase of snow tires makes
sense, as they replace a future set of all-season tires you will have to
buy anyway.
Three principal characteristics distinguish a winter tire from an
all-season tire. The winter tire is made of a softer, spongier rubber
that grips better in colder weather. (That’s also why it has to be
removed for summer use to avoid wearing it out.) The rubber used in a
summer tire becomes hard at 10 C. An all-season tire will stay
flexible to –10 Celsius, and the rubber on a winter tire should stay
flexible to – 30 C.
The grooves in the tire are deeper, and its large blocky treads bite
into snow more aggressively.
A winter tire offers significant safety advantages over an all-season
tire. Braking on ice is better. In comparison tests, the best winter
tires stopped between 30 and 60 feet shorter than all-season tires from
50km/h. Performance is enhanced in deep snow and slush. You’re less
likely to get stuck in a parking spot or to be unable to start on a
steep hill. The advantages become greater as tires wear and the
all-season model starts to perform like the proverbial banana peel.
The disadvantages of winter tires are the additional purchase cost
and inconvenience related to storage and twice-yearly changeover.
The
mountain and the snow flake: A
meaningful logo
The Rubber Association of Canada and its American counterpart have
devised a new, strict snow traction standard for winter tires that was
implemented during the winter of 2001-2002. Tires that meet this
standard display a small symbol depicting a snowflake on a mountain on
their sidewalls. The compliance of a tire with this standard is evaluated by
performing a standardized test on packed snow; tires that achieve a
traction index higher than 110 (compared to a reference tire with an
index of 100) are deemed worthy of bearing the logo. So far, no all
season tires have been able to meet the standard.
The "mountain and snow flake" standard was created because
of the inadequacy of the "M+S" (mud and snow) symbol, which is overused
by the tire industry and for which no standard exists. This absence of
objective criteria resulted in an effort by the industry that also
involved government participation to develop a meaningful standard.
Should I change wheels for winter?
The purchase of inexpensive steel wheels saves the cost of mounting
and dismounting tires twice a year. It also prevents damage to the tire
during installation and saves fragile alloy wheels on many cars from the
corrosive effect of salt used in winter. The additional cost of about
$50 per wheel is recovered within three years from installation savings.
The owners of cars equipped with low
profile tires should definitely consider switching to higher profile
winter tires mounted on wheels of a smaller diameter. Low profile winter
tires are less effective and
tend to facilitate the accumulation of snow within the wheels. For more
information on downsizing the wheels on your vehicle, check the section
about minus
one and minus two conversions in this guide.
Avoid multi-application aftermarket wheels, including wheels that have had
the center hole machined (rough finish). The imprecise fit of this type
of wheel can cause the vehicle to shake at speed and causes excess stress
on the wheel studs which can eventually shear. These wheels are usually offered by independent tire retailers (who can also often provide you
with vehicle-specific wheels), but new car dealerships sell them, too. Wheels designed
specifically for your
car may cost a bit more, but they are worth it.
Winter tire characteristics
The best winter tires offer superior adhesion on ice in
deep snow, with a soft comfortable ride. Handling is less precise than
summer tires.
European winter tires are generally more performance oriented. Handling is
crisper and stability superior at high speed, but adhesion on ice is not
as good.
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