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A Detailed Guide on How to Read Tire Info

A Detailed Guide on How to Read Tire Info

Your tires contain more info within them than you might expect, but that doesn’t do you any good if you don’t know how to read the info. Some of the common questions we get asked about tires include: “What does m+s mean on tires?” and “How do I know what tire size I need?” 

We answer those questions below. 

What Does M+S Mean on Tires? 

M+S simply means mud and snow. Tires with these markings are typically winter tires and perform well on slush and snow. However, they are only true winter tires if your tire also has a snowflake symbol. If they don’t, then they will perform exactly the same as a summer tire in winter conditions when the temperature drops below 7°C. 

Tire info on sidewall

How Do I Find Out What Tire Size I Need? 

On every tire’s sidewall, there is a large cluster of numbers and letters that tell you what size of tire your car is equipped with. For example, one might be P 185/75R15 82S. 

  • The “P” refers to the fact that is a “passenger” tire meant for cars and SUVs versus a symbol like “LT” which refers to a “light truck” designation. 
  • The number 185 is the total width (in millimetres) of the tire. 
  • The number 75 is the aspect ratio of the tire. A lower number (and aspect ratio) is usually chosen by sports car owners that want their car as low to the ground as possible. 
  • “R15” the diameter of the rim in inches. Yes, tire info has both metric and imperial info on it in Canada. No, it doesn’t make sense to us either. This particular tire would need to be mounted on a 15” rim. 
  • The last set of numbers and letter “82S” is the load and speed index respectively of a tire. The load index notes how much weight a tire can handle for the pressure it’s meant to be at. The speed index, on the other hand, refers to the maximum safe speed a tire can reach when fully loaded. 

Again, it’s important to note that winter tires are only legal winter tires in Canada that have a snowflake symbol on them. If you’re not confident that the tires you’re interested in will work for your car, reach out to tire resellers as they can look up your car and let you know if the tires will work for your vehicle. 



Get an affordable and high-quality set of used tires by coming to see us at Top Grade Tire!