How to Distinguish Tire Sizes?
2 Answers
Tire sizes can be distinguished by looking at the sidewall of the tire. The tire size is indicated in millimeters, representing the section width and the aspect ratio as a percentage, followed by the tire type code, rim diameter, and load index. Taking 175/70R14 77H as an example, 175 means the tire width is 175mm, 70 indicates the aspect ratio is 70%, the rim diameter is 14 inches, the load index is 77, and the speed rating is H. The method to measure tire size is: 1. Use a metal tape measure to measure the outer circumference by wrapping it around the tire along the centerline of the tread or a higher point near the centerline; 2. Select a sidewall area without markings, decorative lines, or protective ribs, and use a vernier caliper or caliper to measure the section width at approximately four equally spaced points around the tire; 3. Calculate the data.
I've been helping people at the auto repair shop for 20 years, and distinguishing tire sizes is actually quite simple—just look at the numerical markings on the tire sidewall, such as the common 195/65R15 format. The 195 represents the tire width in millimeters; 65 is the aspect ratio, meaning the tire height is 65% of the width; R stands for radial construction, which most modern cars use; and 15 is the rim diameter in inches. It's crucial not to mix these up—wrong sizes can lead to faster tire wear and unstable drifting while driving. Wider tires offer better grip but higher fuel consumption, while narrower ones save fuel but reduce braking performance. Lower aspect ratios provide precise handling but poorer comfort, whereas higher ones make for a smoother ride over bumps but sluggish cornering. Always match the original factory size when replacing tires—otherwise, the suspension system bears extra stress, affecting the overall driving feel. Daily checks on the labels don’t take much time.
