Standard rim sizes include 5.5 inches for P195/75R15 tires, 6 inches for P215/75R15 tires, 6.5 inches for P235/75R15 tires, 7 inches for P225/50R15 tires and 7.5 inches for P225/45R17 tires. The measuring rim width of a tire increases by .5-inch increments in proportion to increases in the tire section width.
The measuring rim width of a tire, also called the design rim width, determines the width of the tire. The design rim width is an international standard of measure that all tire manufacturers use to ensure that the tires they produce have the same dimensions relative to their physical sizes. Larger tires typically have wider wheel widths, while smaller tires have narrow wheel widths.