UTV Tire Section Width
A tire's section width (also called "cross section width") is the measurement of the tire's width from its inner sidewall to its outer sidewall (excluding any decorations or raised letters) at the widest point. As noted, this measurement is typically in inches but you may see in mm (more typical in automotive tires). This measurement is made without any load placed upon the tire and after the tire has been properly mounted and inflated.
Because a UTV tire's section width is influenced by the width of the wheel, the correct rim width for the tire size being measured must be used. The width of a tire mounted on a narrow rim would be "narrower" than if the same tire was mounted on a wide rim.
The industry rule of thumb is that for every 1/2" change in rim width, the tire's section width will correspondingly change by approximately 2/10".