## What do the numbers and letters on the side of my tires tell me?

The sidewall of your tires holds quite a bit of information that will help you understand what tire your vehicle requires and why.

Example:

I went to our A-1 Tire & Battery website and did a search on a fairly common vehicle.

The example I will use is: P225/55R17 95H

P indicates that you have a passenger type tire. It also indicates that your tire is a P metric tire. Typically this type of tire would go on cars, SUV’s, crossovers, minivans and some smaller sized trucks. Now if your tire starts with LT, then you have a light truck tire. There are tires that begin with ST as well and that indicates that it is a special trailer tire (would be found on your travel trailer etc.) No letter in front of the numbers means you have what is called a Eurometric tire and really the only difference is it may have a different load capacity.

225 this measures your tire from sidewall to sidewall (tire width) in millimetres and varies depending on the rim it will be applied to.

55 is the aspect ratio of the tire and signify the tire’s sidewall profile. The bigger the ratio, the taller the profile. In this example the ratio of 55 means the tire is 55% as tall as the tire’s width. I’m not going to do the math but if you want just convert mm to inches then multiply by 0.55.

R stands for radial tire or radial construction which just describes how the tire is built. This is the industry standard. If you see ZR, this would indicate a high performance tire with a higher speed rating.

17 is the size (in inches) of rim that this tire will fit on.

95 is the load index and the amount of weight that the tire can support. In this case the 95 means that this particular tire will support a weight of no more than 1521 pounds or 690kg. The larger the load index number, the more weight you can carry. On a tire that starts with LT you may also see a letter C, D or E and this indicates the ply of your tire: C= 6 ply, D= 8 ply and E = 10 ply. The larger the ply, the heavier your load capacity.

H is the maximum speed rating of the tire under its load capacity. In this case the H refers to a maximum speed rating of this tire at 210kmph. Not that anyone would be going that fast but it also helps in cornering at higher speeds and maneuverability.

You may also see a few extra letters after the size such as AT which stands for All Terrain = a little more aggressive tire. M&S stands for mud and snow which is still designated as an all season tire and designed for light snow. If you see a snowflake or mountains, these are specific winter tires = softer rubber compound, better traction, siping and different tread design.

Winter tires should be removed before the temperatures go too high otherwise you will wear them out prematurely. I won’t go into too much detail here…… I’ll leave this for another blog down the road.

Remember to check your tire pressures on a regular basis for optimum gas mileage, even tire wear and longer tire life.