What Is the Difference Between 275 70 18 and 275 65 18 Tires?

The difference between these two tires is in their aspect ratio, a comparison between the tire's height and width. The tire's aspect ratio is the tire's sidewall height expressed as a percentage of its width. In a 275 70 18 tire, the sidewall is 275 millimeters x 70 percent or 192.5 millimeters. In the second tire, the sidewall height is 275 millimeters x 65 percent or 178.75 millimeters.