What do the letters on tires represent?
4 Answers
Tires generally have two letters, the first letter represents the tire type, and the second letter represents the maximum speed the tire is allowed to reach. Taking the tire specification 245/45R1896Y as an example: 1. 45: Represents the aspect ratio of the tire. This value usually ranges between 30-80, with a lower number indicating a thinner sidewall. 2. R: Indicates the type of tire. 'R' and 'Z' represent radial tires, 'X' represents high-pressure tires, and '-' represents low-pressure tires. 3. 18: Indicates the wheel size the tire is suitable for. The number 18 means this tire is suitable for wheels with a diameter of 18. 4. 96: Represents the maximum load a single tire can bear. The higher the number, the greater the load the tire can withstand. 5. Y: The so-called speed rating, which is the maximum speed the tire is allowed to reach. Different numbers represent different speed levels. Exceeding the maximum speed of the tire may lead to dangers such as a blowout.
The combination of letters and numbers on the sidewall of a tire is like its ID card, for example, 215/55R17 94V. The first number, 215, represents the tire width in millimeters; the number after the slash, 55, is the aspect ratio, which is the percentage of the tire's thickness relative to its width; R stands for radial construction; and 17 indicates that it fits a 17-inch wheel. The last set of numbers and letters is the most important: 94 is the load index (corresponding to a single tire load capacity of 670 kg), and V is the speed rating (maximum speed of 240 km/h). When I last changed my tires, I paid special attention to these two parameters, as they directly relate to driving safety. There is also a four-digit number on the sidewall, such as 1823, which indicates the tire was produced in the 18th week of 2023. When replacing tires, it's best to choose fresher ones for better durability.
As a seasoned driver with over 20 years of experience, I can explain tire parameters with my eyes closed. Take the common 235/45ZR18 as an example: 235 is the tread width, 45 indicates the sidewall height is 45% of the width (aspect ratio). The letter Z signifies a high-performance tire, while R denotes the tire's construction (no need for further explanation). The key details are the load index and speed rating at the end - like my car's 98Y: 98 means each tire can bear 750kg, and Y indicates a maximum speed of 300km/h (though I'll never actually drive that fast). The DOT code reveals factory information and production date - when buying tires, check the last four digits; for instance, 1124 means the tire was manufactured in the 11th week of 2024.
People who are into car modifications are very particular about their tires. Beyond the basic size specifications, the 3T index on the tire sidewall is especially crucial: the first T represents the treadwear rating, and the 320 I chose is quite durable; the second T indicates the traction grade, with AA being the strongest; the third T is for temperature resistance, with A being the best. When modifying, you also need to pay attention to the rotation direction arrow on the outer side of the tire—installing it backward significantly reduces water drainage. Once, I noticed a snowflake mountain symbol hidden in the tire grooves, indicating winter tire performance certification. Recently, I discovered some tires have small letters like "MO" printed on the side, which I later found out stands for Mercedes-Benz original equipment certification.
