What is the size of car wheels?
3 Answers
Tire models are clearly marked on the side of the tire. The tire model refers to the internationally standardized tire code, which represents the section width and aspect ratio percentage in millimeters, arranged in the following order: tire type code, rim diameter (in inches), load index (or load capacity index), and maximum speed code. Below is an introduction to tire sizes: 1. Introduction: Tire sizes are printed on the sidewall, with two representation methods, such as 34*7 or 7.50-20. The former indicates high-pressure tires, while the latter indicates low-pressure tires. 2. Tire markings: There are many markings, for example, D is used for light vehicles, F for medium-sized vehicles, G for standard vehicles, and H, L, J are used for large luxury and high-performance vehicles.
After driving for ten years, I've realized that wheel size isn't a single measurement—it actually consists of two parts: rim diameter and tire width. When we commonly refer to 16-inch or 18-inch wheels, we're talking about the rim size. SUVs often use larger rims ranging from 17 to 20 inches, which look more imposing but compromise comfort, while compact cars with 15 to 16-inch rims tend to be more fuel-efficient and quieter. The three-digit number representing tire width indicates the contact patch—tires with widths like 195mm or 225mm provide better stability at high speeds but consume more fuel. When upgrading to larger rims, you must consider the shock absorber height to avoid rubbing against the wheel arches, and incorrect sizing can also affect ABS and tire pressure monitoring systems. Additionally, if the spare tire size differs from the main tires, it should only be used temporarily.
Last week when I was helping my neighbor choose wheels, I noticed many people only focus on rim size. Indeed, wheel diameter matters a lot, ranging from R15 to R22. While large rims look great on coupes, they can be bumpy over speed bumps. However, the aspect ratio number on the tire sidewall, like 65 or 45, is equally crucial. The smaller the number, the thinner the tire - better for cornering stability but more prone to bulging. The most obvious issue with incorrect sizing is speedometer inaccuracy; larger rims increase circumference, making actual speed 5% faster than displayed. I've seen cases where improper sizing caused heavier steering and wheel arch rubbing, so always consult your vehicle manual or repair shop to confirm parameters before changing sizes.
