What do the numbers on car tires represent?
3 Answers
The meaning of the numbers on car tires: Taking 255/45R20 as an example: 255 represents the tire section width, 45 represents the aspect ratio, which is the ratio of the tire sidewall height to the tire section width, R indicates that the tire has a radial structure, and 20 represents the outer diameter of the rim. The tire tread width, measured in millimeters, refers to the contact area between the tire tread and the ground. The larger the contact area, the greater the tire's grip, and correspondingly, the greater the resistance. Tires are often used under complex and demanding conditions, enduring various deformations, loads, forces, and high and low temperatures during operation. Therefore, they must possess high load-bearing performance, traction performance, and cushioning performance.
As someone who drives to work regularly, I'm quite familiar with the numbers on tires. For example, in the common 205/55R16 sequence, 205 represents the tire width in millimeters, indicating how wide it is; 55 is the aspect ratio percentage, showing the sidewall height as a proportion of the width; R stands for radial construction, which most cars use nowadays; and 16 is the wheel diameter in inches. The numbers also include a load index like 91, indicating the maximum load capacity—the higher the number, the more weight it can bear. Speed ratings such as H represent a maximum speed of 210 kilometers per hour. The DOT code shows the manufacturing date, with the last four digits like 1223 indicating the 12th week of 2023, reminding us not to use old tires to avoid safety hazards. When replacing tires, always verify these parameters match the original vehicle specifications, as mismatches can affect handling stability and increase fuel consumption. I've learned from experience that regularly checking tire pressure and these numbers helps reduce unexpected risks.
I just started learning to drive not long ago, and my friend taught me how to read tire numbers. Those numbers printed on the sidewall, like 195/65R15, where 195 is the width in millimeters—a larger value means more stability but slightly higher fuel consumption; 65 is the aspect ratio percentage—a smaller value means lower sidewalls and more agile cornering; R stands for the construction type; and 15 is the wheel size in inches—make sure it matches the rim size to avoid buying the wrong one. Then, in the numbers like 91H, 91 is the load index—the higher the number, the more weight it can carry, like passengers and luggage; H is the speed rating—the letter H corresponds to 210 km/h, so if you often drive on highways, choose the appropriate symbol to ensure safety. Finally, don’t forget the DOT code to check the production date—the last digits, like 2217, mean the 22nd week of 2017, to avoid using aged tires. Now, when I buy tires, I pay special attention to these points—it saves money and could be life-saving, simple and practical.
