If you are like most people, the markings on the side of your tire are nothing more than nonsense. They may look strange at first, but once you’ve read this short guide, you will be able to read and understand the markings on any tire.

Tires manufactured in the United States start with a letter, defining the type of tire. “P” for passenger, “LT” for light truck. European manufacturers don’t include this letter.

The first three numbers tell you the width of the tire in millimeters, measured from one side of the tire to the other. Most car tires have widths between 150mm to 250mm.

The aspect ratio is the difference between the width and height of a tire.

The next section, usually separated from the tire width measurement by a “/”, indicates the aspect ratio of the tire. The aspect ratio is the difference between the width and height of the tire. e.g. If the number is 50, the height of the tire is 50% (1/2) of the width of the tire.

After the aspect ratio comes the tire’s radial measurement. This measurement starts with the letter “R”. The number after “R” indicates the diameter of the wheel, which the tire was designed to fit. Most car wheels have a diameter between 14″ to 17″.

Now you know how to interpret a tire’s measurements, you can feel more confident when speaking with a vehicle technician. Occasionally you may see other values printed on a tire, but these typically relate to speed ratings, rather than size.