What Does 300/75R15 Actually Mean?

Let's break it down simply: The 300 means this tire has a tread width of 300 millimeters. The 75 is the aspect ratio, which means the sidewall height is 75% of that width. The "R" stands for Radial construction (the modern standard for safety and durability), and finally, the 15 indicates that this tire perfectly fits a 15-inch wheel.