How to Read Tire Sizes (265/70R17 Explained)

Breaking Down the Numbers: 265/70R17

Let's use one of the most common truck tires on the planet: 265/70R17.

1. 265 (Section Width): The very first number is always the width of the tire measured in millimeters from the widest point of the inner sidewall to the outer sidewall. In this case: 265mm.
2. 70 (Aspect Ratio): This is where it gets tricky. "70" is not a measurement in inches or millimeters; it is a percentage. It tells us that the sidewall height is literally 70% of the 265mm width.
3. R (Radial): This letter denotes the internal construction of the tire. "R" stands for Radial, meaning the internal ply cords radiate at a 90-degree angle to the direction of travel. Nearly all modern tires are radials.
4. 17 (Wheel Diameter): The final number tells you what size metal rim this tire needs to be mounted to. This tire only fits on a 17-inch wheel.

Visualizing the Metric System

Unlike flotation sizes (e.g., 35x12.50), metric tires require complex math to find the overall height. You have to convert the 265mm to inches, find 70% of that to get one sidewall height, multiply it by two (top and bottom sidewall), and add the 17-inch rim.

(Formula: [[265 / 25.4] * 0.70 * 2] + 17 = 31.6 inches tall).

Practical Recommendations

If you want to go wider but keep the same height, look for a lower aspect ratio (e.g., 285/65R17). If you want to go taller without causing horrible rubbing by being too wide, keep the width but increase the ratio (e.g., 265/75R17).

Calculator Integration

Don't want to do that math? Use our TireFitPro calculator to compare tire sizes and check if they will fit your vehicle without rubbing or speedometer issues. We convert everything automatically!