How to buy winter tires economically

Every year fall rolls around and people in Canada, the northern States, and Nordic countries start thinking about buying winter tires for their cars. Although you can drive around on "all-season" tires year round, their performance in snowy and icy conditions is dismal. In Canada, "all-season" really means three season (or May-August, depending on where you live).



Buying a set of winter tires doesn't necessarily cost you any more in the long run if you plan to keep your car for a few years. Since you'll be using each set of tires for only half the year, your summer or all season tires will last twice as long as if you used them year round. In fact, due to the better traction of winter tires in slippery conditions, you could save money by avoiding potential collisions.

Tires are not a very complicated looking part of the car but the wide variety of sizes, brands, and prices can make buying them a confusing experience for someone who hasn't done it before.

Determining the size
Every car has a specific size of tire that it comes with, and any new tires that you put on the car have to be pretty close to the original size. Significantly changing the diameter of the tire will cause your speedometer and odometer to display incorrectly, and may affect ground clearance, handling, and fuel consumption. That being said, actual tire sizes vary from one manufacturer to the next even if the nominal size written on the sidewall is the same. Being within a few percent of the original size is good enough.

Tire sizes are usually specified using a number such as 225/60R16 98S. This is a strange measurement system that mixes imperial and metric units. The first number specifies the width of the tread in millimetres, in this case 225mm. The second number tells you the sidewall height as a percentage of the tread width, in this case 60% of 225mm (or 135mm). The third number is the diameter of the wheel rim in inches, with 16" in this case being equal to about 406mm. The final number and letter combo, 98S, is the load and speed rating. Looking that number up in a table such as this one at Tire Rack tells us that the tire is rated to 750kg and 180km/h.

The simplest thing to do is buy a tire that's exactly the same size as your original one, so I would be looking for a 225/60R16. The load and speed ratings for winter tires may not match the original summer tires, but pick a load rating that's at least 25% of your max gross vehicle weight and a speed that's faster than you intend to ever drive on those tires. You do, however, have some flexibility with tire sizing, which is good since not all manufacturers make all available sizes (or the original size may not be available in your area). The important consideration is to keep the overall diameter of your new tire close to the diameter of the old one (within 3% is the accepted rule of thumb) and the width of the tread to within 20mm of the original.

To find the overall diameter of a tire, simply add up the diameter of the rim in mm, and the height of the two sidewalls. For a 225/60R16 tire the diameter is 406mm (rim) + 2 x 135mm (sidewalls) = 676mm. I can use a 215/60R16 tire (664mm diameter, or 2% smaller), a 205/65R16 tire (672mm diameter, or 1% smaller), or a 215/65R16 tire (685mm, or 2% larger). Going to a wider winter tire than your original is not recommended as wider tires have lower ground pressure. This is good if you're trying to cross the arctic by riding over the snow drifts but for regular road use you want the tire to dig through the snow down to the hard surface below. Using a tire that's more than 20mm narrower than the original could be a problem as it may be too narrow for the rim.

New or used?
Most people don't consider buying used tires as it's a consumable item, and it seems like you wouldn't be saving anything for the trouble. However, winter tires can last many seasons with moderate use and people often sell their cars without including the second set of tires, leaving them with a set that won't fit another vehicle. With a bit of careful shopping you can find a set of tires with over 80% of the tread left on them for less than half the price of new ones.

If you do decide to buy used tires, make sure you compare the price to an equivalent set of new tires. The prices of winter tires can vary substantially by brand and by size. A cheap Goodyear Nordic for a small car can be less than $100, whereas a Blizzak for a larger SUV could be over $300. When you find a used set of tires listed on Kijiji, Craigslist, or your local paper, look up the same brand and size at shops near you to compare. The price you pay for a used set of tires will depend on the tread left on them, but as a rule of thumb I would say pay half price for tires with >75% tread, and a quarter of the new price if they have >50% tread. If they have less than half the tread remaining I would steer clear, unless the car you are driving will only last another year or so.

One thing to keep in mind when buying used tires is that most shops will charge you for mounting and balancing tires that you bring in yourself, whereas they should include this service for free if you buy tires from them. Expect to pay anywhere from $10 to $25 per tire to get them mounted and balanced, but shop around for the best deal (just try not to get it done at Canadian Tire).