Tire Centre

When we think of tire maintenance, usually the first thing that comes to mind is tire pressure. It's no secret that properly inflated tires last longer and optimize fuel economy. In fact, for every one pound per square inch (psi) below the recommended pressure, your fuel economy decreases by 0.4 percent. For example, if your tires are five psi low (which is not uncommon), your fuel economy will decrease two percent.

You should get into the habit of checking the pressure in your tires at least once a month, or whenever you experience ambient temperature extremes. Air contracts when it cools, so a quick cold snap could leave your tires underinflated.

Always refer to the tire decal on the door jamb for the minimum load pressure and tire size information. Refer to the tire sidewall for maximum load pressure. Remember that the tire pressure recommendation is for an ambient temperature or "cold" tire. Therefore, tire pressure should be checked when the vehicle's tires are "cold", not after extensive driving. Tires heat up after extensive use and with this heat, comes increased pressure. Keep a tire gauge in your car or truck so you can quickly check tire pressure any time.

After checking the tire pressure, visually inspect the tires. Look for any abnormal wear patterns, A, that might indicate an alignment problem, such as a worn outer edge of a front tire. If the tread is looking a little thin, check the tread depth.

Some people use a penny, but for maximum accuracy use a tread depth gauge, B. If you're down to 3/32" of tread, it's time for new tires.

If you don't have a tread depth gauge, check the wear bars, C. Wear bars are small horizontal bars in the base of the tire grooves. When the wear bars are even with the tread, it's time for some new rubber.

Finally, if you have been experiencing a slow air leak, it's a good bet that a nail, screw or some other foreign object, D, has penetrated the tire tread.

When it's time to buy new tires for your car, the one thing that you must remember is to buy the correct size tire. That means if your vehicle has 16-inch wheels, you must install 16-inch tires. If you want to put a larger tire on your car or light truck, you're going to have to buy new wheels. The tire size information is moulded into the sidewall of the tire. Let's look at an example: 225/60R16. Reading the size from left to right, the first number is 225. This is the section width, E. This three-digit number is the width of the tire from the widest point on the outer sidewall to the widest point on the inner sidewall when the tire is mounted on a specified width wheel.

The second number is 60 and this represents the sidewall aspect ratio, F. In this example, the sidewall height of the tire is 60 percent of the section width. If the aspect ratio was 50, then the sidewall height would be 50 percent of the section width. The lower the number, the shorter the sidewall. You've probably seen those big 20- and 22-inch “DUB” wheels with the narrow sidewalls. Those tires most likely have an aspect ratio of 40.

The R indicates that the tire has a radial construction, which is the case of the vast majority of tires made today, G. If the tire has a Z speed rating, the Z will precede the R. It is the only speed rating shown in the tire size.

The last number, 16, is the tire and wheel diameter designed to be matched together, H. In other words, this tire, which has a 16-inch rim diameter, must be mounted on a 16-inch diameter wheel. The trend in recent years has been to larger tire and wheel sizes, both on new cars and in the aftermarket. Just remember to match the size tire to the correct size wheel.

To the right of the tire size is the service description. This is a two- or three-digit, one-letter code. In this case, it's 98T. 98 represents the load index, I, which is used to compare relative load carrying capabilities of a tire. The higher the number, the greater the load carrying capacity. Load index numbers range from 71 to 110.

T is the speed rating of the tire, J, or the fixed maximum speed capability of a new tire. Family vehicles commonly have a speed rating of S or T (180 km/h [112 mph] and 190 km/h [118 mph], respectively). The highest rating used to be Z, which is 240 km/h (149 mph), but W and Y were added to indicate ultimate performance for exotic sports cars.

The last tire ratings to examine are the Uniform Tire Quality Grade (UTQG) standards. These three ratings allow consumers to rate tires on a comparative basis for treadwear, traction and temperature capabilities. The treadwear rating, K, is a three-digit number indicating the relative treadwear compared to a test tire. The test tire is established as 100. A rating of 200 means that tire has twice the treadwear as the test tire, 400 means four times more than the test tire, and so on.

The traction rating, L, is a letter code - AA, A, B and C - that rates the straight line wet coefficient of traction as the tire skids across a specified test surface. AA is the highest rating and C is the lowest.

The last parameter is temperature resistance, M, or the ability of a tire to operate at high speeds without failure. The highest rating is A and the lowest is C.