The string of numbers and letters imprinted on the sidewall of your tires are rich with information — if you know how to read them. Every tire is marked with its size, load rating, what speeds it can handle, and even the date of manufacture to learn how fresh the rubber is.
But let’s start with the most important numbers — the ones you want to have in hand if you have a puncture and you need to call a dealer about getting a replacement. They might read something like 225/65R17. Let’s break that down:
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- 225 is the section width, in millimeters.
- 65 is tire’s aspect ratio, representing the height of the tire sidewall indicated as a percentage of the tread width. The 65 in the 226/65R17 example means the sidewall’s height is equal to 65 percent of the tire’s width.
- R indicates the tire’s construction type. In this case, it’s an “R” for “radial” construction – which is what you would typically find. You may also see “RF” which indicates a self-supporting “run flat” tire. A specialty tire might carry an X, B, a dash, or D — indicating “diagonal” or bias-ply construction.
- 17 is the diameter of the wheel in inches.
Sometimes that string of numbers has a letter or two in front of it – often you’ll see “P” which indicates a tire designed for passenger vehicle use. You’ll also see “HL” indicating a higher load carrying capacity, a “T” for a temporary spare tire, or “LT” for light truck.
Winter tires are designated with an icon showing a three-peaked mountain with a snowflake in the centre of it, while tires with some light winter capacity tires show an “M+S” which stands for “mud and snow.”
Other numbers on your tire are the Uniform Treadwear Quality Grading, which indicates a tire industry standard performance rating for treadwear, traction, and temperature.
And finally, the DOT code consists of the manufacturer’s plant code, the tire size, brand, and the date of manufacture. The numbers that might interest you in the string of characters after “DOT” is the last four digits, which represent the production week and year. If the code is, “DOT: FDAP LJO 2320” then the tire was produced in the 23rd week of 2020.
For more than you ever thought you wanted to know about tire markings, there’s a comprehensive guide further breaking down the codes here: (https://simpletire.com/learn/tire-buying-guides/how-to-read-tire-size).