What do numbers on tires mean?

You might not realize it, but a tire is one of the most intricate components of a vehicle. The tread life of a tire, the proper pressure, rotation schedules, and tread patterns are just a few of the many topics that can be confusing. The numbers on the sidewall of a tire, though, can be the most perplexing feature for a driver.

Despite the fact that the sidewall numbers on your tire may be confusing, the sidewall of your tire contains the code that explains what your tire can do. Here you will find information on how to read those digits and why they matter. What do the numbers on your tires mean?

The numbers on your tires

The numbers on your tires serve as descriptions. They provide information about the tire's size, weight, maximum allowable pressure, and even the speeds it can withstand. By matching the descriptors found on your set, you can obtain a reliable replacement for that tire. Moreover, you can find out what the tire is good for by decoding the combination of the numbers and letters on the sidewall.

Of course, the number varies depending on the size of the tire, but the letter "R" does not. On the sidewall of a tire, you may notice two types of letter to denote construction: Radial or Bias Ply. Radial tires are the most common type of tire on the road in the United States today, so the letter "R" is usually included in the tire size designation.

The brand name and size are two elements that stand out on a tire's sidewall. Although tire sizes have a specific format, you can readily decode them. Three groupings of numbers are visible, and each group stands for a different dimension. Those three groupings of numbers are classified as tire width, aspect ratio, and rim diameter.

Let's understand them using the tire size P225/65R17 as an example.

Tire width

The dimension from one sidewall to the next is always referred to as the tire width. The distance between the sidewalls of the tire is measured in millimeters. In this instance, the sidewalls are 225 millimeters apart. The width of the appropriate tires for your vehicle, in millimeters, is the first number to appear in your tire size information: P225/65R17.

Aspect ratio

One of the dimensions that is by far the most misinterpreted is "65", which represents the aspect ratio. The following number you see after the slash represents the aspect ratio of the tire, which effectively indicates how tall the profile of your tire is: P225/65R17. Deliveries of aspect ratios are made as percentages. Dividing the tire's height off the rim by its width you will get the aspect ratio.

When a tire's aspect ratio is 65, its height is equal to 65% of its width. This is the sidewall's height from wheel to tread in relation to width. The sidewall is 146.25 mm tall if the width is 225 mm. Remember that this doesn't tell us how tall the tire is overall.

Rim diameter

The rim's diameter code, expressed in inches, is the last number, which is where the tire can be mounted. A tire with the dimensions P225/65R17, for instance, would fit a rim with a 17-inch diameter. The wheel's size is determined by measuring it from end to end.

How to read numbers on tires

On the sidewall of your tires, you can find some more numbers, so how do you read them? The load index is the next biggest number on the sidewall of your tire. In essence, this indicates how much weight, in pounds, the tire can support when completely inflated.

The load range may be listed below the load rating in a font size much lower than that. This is an alphabetical character that basically explains more about the design and constraints of the tire. The highest speed that a tire is capable of is indicated by its speed rating. Next, we have the DOT numbers on tires that are represented by the 12-digit number you can see. It provides information about the date the tire was made.

For instance, a tire with the code 2320 at the end would have been produced during the 23rd week of 2020. This is a crucial number to pay attention to because it indicates the tire's age and if it is suitable for use. In addition, you can find three numbers appear at the top portion of the tire sidewall. These numbers fall under the category of Uniform Treadwear Quality Grading and tell us how well a tire actually performs.

The traction grade is represented by the following two-digit code. This number is found by measuring the g-force rating produced. Your tire’s temperature grade comes next. This rating simply tells you how much heat the tire can withstand without starting to degrade, which compromises performance and safety. The last number, M+S, indicates that the tire can handle light mud and snow.

What do the numbers on tires mean for different types of vehicles?

If you are looking for off-road tires for a light truck or SUV there is one more sizing type to be aware of, it's known as a Flotation size. And the numbers in this sizing format except for a few key differences, are similar to LT-Metric tires in application. The letters LT will appear after the Rim Diameter, indicating that this tire type, like the LT-Metric and Euro-Metric Commercial (C-Type) tires, is intended for Light Truck vehicles.

A P-Metric tire will have the letter “P” at the starting of the “Tire Size” which refers to tires manufactured in the United States to specific standards and intended for passenger vehicles (NOTE: this could include coupes, sedans, CUVs, SUVs, minivans, pickup trucks, and even some cargo vans). If a tire size has no letters at the start, it is a Euro metric tire. The load capacities of P-Metric and Euro-Metric tires may differ. The M+S symbol may appear as an alternative and is commonly found on an all-season tire to let us know it has enough tread void to potentially handle mud and snow. Additionally, winter and all-weather tires (and some all-terrain tires) typically have a Three Peak Mountain Snowflake symbol on their sidewall, which denotes that they can handle severe ice, slush, and snow.

Conclusion

The sidewall of your tire contains all of your tire's information in the form of numbers and letters. Do you still have questions about reading your tire’s sidewall? Give us a call and our experts will be more than happy to provide you with any information and assist you in finding the ideal match for your vehicle.

FAQs

What do the numbers and letters on tires mean?

The numbers and letters on a tire denote the tire’s size, load index, speed rating, type, brand, manufacture date and location, and some performance features.

How do you read the numbers on a tire?

The sidewall of your tires contains vital information. The best way to comprehend this is to break it down into letters and numbers. The tire size is determined by the combination of three groups of numbers and two letters. Then there are numbers and alphabets that will tell you about your tire's tread life, traction, temperature grade, speed rate, load rate, and so on.