Halderman:
The width of the tire is not the width of the tread but instead is the “cross-sectional” width so this is why I think your measurements are not aligned to the size. The section width (245) is the maximum width of the tire (widest part of the sidewall) of the tire mounted on the nominal wheel width (as specified by the Tire and Rim Association) and inflated. The section height (45) is 45 percent of the section width. This includes the bead area which is below the wheel lip and is not visible/measurable when the tire is mounted. A 17-inch wheel is 17 inches. Diameter is measured where the tire bead sits, not the visible diameter of the wheel with a tire mounted.
Also, please note that tire size can vary by tire manufacturer. In fact, one “green” tire, as an uncured tire is called, can be made in many different sizes of tires, depending on which mold is used. In other words, while it appears to be very detailed as to the width and height that the tire should be, it is far from true for many tires. That is why it is recommended that the same size and brand of tire be used on the vehicle – especially all-wheel and four-wheel-drive vehicles.
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