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(iStock photo) (iStock)

It's that time of year again — when most drivers across the country are wondering whether there's enough money in the budget to buy winter tires. Of course, if you live in Quebec, that choice has been made for you. The province is the only jurisdiction in the country to require that every car be equipped with four winter tires between Dec. 15 and March 15 every year.

How do I know if my tires are worn out?

All tires come with tread wear indicators. These are small bands of rubber between the tread blocks of a tire. When the tread is worn down to the level of the indicator, it's time to change your tires.

A tread depth of three mm is about the limit for all-season and performance tires. Winter tires are considered worn out when the tread depth dips below six mm.

Another sign that your tires are at the end of their useful lives: cracks appear in the rubber. The tires can no longer be considered safe to use.

The law — which was passed early in 2008 — put pressure on supplies in parts of the country and even led to some tire thefts by the fall.

In New Brunswick, buses that transport students must also be equipped with winter tires. 

Law or no law, there are plenty of good reasons to invest in a set of four winter tires.

They're designed to improve traction not just on snow and ice but also in cold weather. Winter tires will help your car brake more efficiently in conditions with heavy snow and ice. They work by constantly clearing themselves of snow as they roll, which allows for more consistent grip.

Winter tires are made of a rubber that maintains its elasticity in much colder temperatures than other tires. They'll stay soft down to -40 C, while summer tires and all-season radials begin to harden and lose traction at around 7 C.

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Winter tires have better traction on snow and ice because they retain their elasticity in colder temperatures than all-season radials or summer tires.

The Canada Safety Council warns that, contrary to popular belief, winter tires should be installed on all four of a car's wheels and that all four tires should have the same tread patterns. In the past, it was common for drivers to install winter tires on their front wheels only — because rear-wheel drive vehicles were the norm at the time. Using only two winter tires, regardless of whether the car is rear-wheel or four-wheel drive, robs the car of necessary traction.

When your car brakes, weight transfers to the front, so if you have winter tires on the front you will get good traction there and still be able to steer. But if you only have all-season tires on the back, your rear brakes can lock up and the car becomes unstable. It can go into a spin.

Dave Redinger, a Toronto mechanic, says winter tires are crucial to your driving safety.

"SUVs take off like crazy. Most of them are four-wheel drive but, without winter tires, they don't stop any better than anything else out there."

Winter tires are made with rubber that retains its elasticity at lower temperatures, but that does not mean they will wear out more quickly than other tires.

Manufacturers say winter tires should last six seasons. Transport Canada says they could be good for up to 10 seasons. Redinger disagrees.

"By six years, much of the tread is worn. If you want to find out how old your tires are, there's a DOT number on the side of the tires - the last four digits are the year they were manufactured."

Winter tires that have met snow traction requirements are marked with a snow-peaked mountain and snowflake.

A tire for all seasons?

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The mountain and snowflake symbol is displayed on all approved winter tires.

All-season radial tires (sometimes called four-season tires or mud and snow tires) are designed to perform safely in a variety of weather conditions, including during parts of the winter. They are not, however, guaranteed to function properly in heavy snow or on ice and can lose traction when temperatures dip below freezing.

All-season tires are usually guaranteed to last for more than 100,000 kilometres.

The Canada Safety Council says all-season tires can be used in areas of the country that typically experience very mild winters. Drivers on the coast of British Columbia might be able to get away with using all-season radials throughout the winter, but most of the rest of the country wouldn't.

Safety experts warn that the terms "all-season" and "mud and snow" are misleading, since these tires are not designed for the winter weather most of the country experiences.

Transport Canada says tires marked "M + S" (Mud and Snow) or "all season" that do not include the peaked mountain with snowflake symbol may provide safe performance in most weather conditions, but they're not designed for snow and ice-covered roads.

The limits of summer tires

Summer tires (sometimes called performance tires) are built to handle dry and wet conditions, but not snow or ice. They are designed to handle summer conditions better than all-season tires but should never be used in the winter.

These tires are made from softer rubber than all-season or winter tires, and therefore may have a shorter lifespan. Many makes are guaranteed for 100,000 kilometres, but it should be noted that the period during which these tires are regularly in use is longer than the peak periods for all-season or winter tires, meaning they are more likely to wear out after use over a shorter period of time.