How is tire width calculated?
2 Answers
International standard tire codes represent the section width and aspect ratio in millimeters as a percentage, followed by the tire type code, rim diameter in inches, load index, permissible load capacity code, and permissible speed code. More details about tire dimensions are as follows: 1. Introduction 1: Tire dimensions are printed on the sidewall and can be represented in two ways, such as 34*7 or 7.50-20. 2. Introduction 2: The former represents high-pressure tires, while the latter represents low-pressure tires. There are also many other markings, such as D for light vehicles, F for medium-sized vehicles, G for standard vehicles, and H, L, J for large luxury and high-performance vehicles. 3. Introduction 3: If an R is printed on the sidewall, such as 175R13, it indicates that the tire is a radial tire with a width of 175mm (6.9 inches), mounted on a rim with a diameter of 13 inches (330mm). The word RADIAL is usually also engraved on the tire.
I noticed that the tire width is indicated in that string of numbers on the sidewall, like 205/55 R16. The first number, 205, refers to the tire width in millimeters. Last time I changed tires, I specifically asked the mechanic about it. He said this number is measured from the widest part of the tire to the edge of the rim, and there might be a slight deviation when actually mounted on the vehicle. Choosing tire width is quite particular—wider tires offer better grip but consume more fuel, while narrower ones save fuel but are prone to slipping in the rain. For example, my SUV originally came with 235-width tires, but once I opted for cheaper 225-width ones and felt the car drifting during turns. My friends who are into modifications often say that increasing tire width by 10 millimeters requires changing the rims as well, otherwise, it might rub against the brake calipers and cause issues during inspections. I remember the tire shop owner always emphasizing that a change in tire width exceeding 3% can affect the accuracy of the speedometer.
