How to Understand Tires

It's hard to know exactly what the sequence of numbers and letters on the sidewall of a tire equates to. Knowing that information can help you decide what tire is right for your vehicle, driving style, and road conditions. Keep reading if you've ever been left scratching your head when it comes to understanding all of that imperative tire data!


Some of the information is fortunately mandated by government regulation and it gives a description of the tire's size, intended use, capacities and manufacturing source. Luckily, the majority of the information has been standardized, so similar data is found in the same place on most tires.


"The consumer really doesn't have any packaging like they would with another product, where you have a box that would tell you about it," says Keith Willcome, a project engineer at Bridgestone Americas. "Tires are a little bit unique in that way."


  1. Brand and model. The largest type on the tire's sidewall is going to showcase its brand and model. While that's basic information, it's important to keep in mind that if shopping for a used car you will want to walk around and make sure that all four are matching. If you are replacing your vehicle's tires you can reference your car's owner's manual to determine the minimum specifications.

  2. Width of the tire. If you drive a passenger car or light truck, your tires are likely going to use the same form to describe their size. If the sequence begins with a "P" that indicates that it is a passenger car tire, while LT indicates that it is a light truck tire. However, many tires will not have an alphabetical prefix, so don't be alarmed if your tire's sequence starts with a number. The first three-digit number is the tire width in millimeters measure at its widest part, not the tread. This is also called the section width.

  3. Height of the sidewall. The next two-digit number following the slash is the tire's aspect ratio. It's the sidewall height expressed as a percentage of the tire's width.

  4. Wheel size. The final part of the sequence is a letter denoting its construction and the size of the wheel that it is designed to fit measured in inches. You usually won't see anything other than an R for the design of the tires.

  5. Maximum load tire can carry. The following set of letters and numbers are the tire's service descriptions which indicates how much weight its designed to carry. This is called the load index and you can find the recommended tire load range for your specific vehicle by looking at the tire placard on the inside of the driver's door or the vehicle's owner manual.

  6. Speed rating. The final letter in the service description is the tire's speed rating, or the maximum speed that it's certified to safety be driven when properly inflated and maintained.


If you're in the market for a new MINI please view our inventory of 2018 MINI models here and come see us to test drive your dream car today! We'd be happy to answer your questions and begin the financing process!


MINI of San Antonio is a new and used car dealership that provides vehicles to customers all over Texas. We have customers come in from Canyon Lake, New Braunfels, Austin, Kirby, Allen, Boerne and many more cities. Let us know if you have any questions.


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