5 Proper Ways to Read Tyre Size

Car owners often don’t think about all the markings on the sides of their tyres. They figure that knowing the brand and model of their tyre is good enough if they ever need to replace one. However, there are also markings that pertain to the size of the tyre and the safety standards set forth by the federal government. The markings are supposed to be proof that the tyre satisfies these safety standards and size requirements. Aside from that, the Uniform Tyre Quality Grading code will be marked on the tyre too. This will provide information about the maximum amount of inflation pressure, load, and speed allowed for the tyre.

When someone needs to purchase a new tire, they’ll usually go to an auto professional and have them determine the size of the replacement tire needed. But you can save a lot of money by figuring out this information yourself. All it takes is for you to understand the markings on the sides of the tires. Below are 5 proper ways to read the tire size.

1. Tyre Type – Before you worry about the specific size measurements of the tire, you need to first make sure it is the right type of tire. After all, there are tires made specifically for passenger cars, light trucks, and so on. To find out which type of tire you have, look at the sidewall of the tire. You should see a series of numbers that start with one or two letters. If the numbers start with a P, then it means that the tire is for passenger cars. If it starts with an “LT,” the tire is for light trucks.
2. 2. Tyre Width – Some tires will list the width in millimeters and others will list it in inches. If you see three numbers on the tire’s sidewall coming after the previous letter mentioned, then these numbers represent the total millimetres of the tire’s width. If you see two numbers after the letter, then it is in inches. The width is measured from one side of the tire straight to the other side.
3. 3. Aspect Ratio – After the tire width, there will be a forward slash followed by an aspect ratio number. The aspect ratio is another way of saying the ratio of the width of the sidewall to its height of it. The ratio number is the percentage of the width which determines the height. For example, if the aspect ratio is 60, then 60% of the width of the tire will equal the height.
4. 4. Tyre Construction – The double-digit aspect ratio number is often followed by a letter. This letter represents the type of tire construction. The most common letter found here is “R” which stands for radial. A professional auto mechanic will understand what the letter here means. Radial is the most common construction technique used for making tires. Some other less common letters you might find here are “B” for belted bias or “D” for diagonal bias.
5. 5. Wheel Diameter – The final number which is listed at the end is the wheel diameter size. This number will most likely be in inches and it determines the size of the wheel that can fit inside the tire. For example, if you see the number 18 at the end, then it means the tire can fit any wheel that is 18 inches in diameter.

Now you know the basic ways of reading tyre sizes. In most scenarios, you can just copy the numbers and letters that you see on the sidewall of your tyre and then find a new tyre that has those same numbers and letters. However, it is still important that you know what they mean in case you need to ask around for the right tyre size