What Is The Rim Width Range For A Tire?

Much like your foot can sometimes fit in a half size up or down shoe, tires have a range of rim widths they can be mounted on while still performing as designed. Likewise, similarly to how a person typically knows their "shoe size," tires have a measuring rim width from which the tire’s specs are taken. While most measurements in modern tires stay relatively consistent as the rim width changes, section width (the distance across the widest part of the tire) is one that is affected by the change, albeit slightly.

A tire measured on a narrower rim width than the measuring rim width has a slightly skinnier section width as a result. The reverse is true also, where if the tire is mounted on a wider wheel width, the section width is slightly wider. The accepted industry's rule of thumb to quantify this change is, for every half inch change in rim width, the tire’s section width will change by approximately 2/10".

For example, a 205/60R15's measured rim width is 6.0". So the tire is mounted on a 15" diameter wheel that is 6" wide and measured for the published section width and other tire specs. In this case the tire's section width is 8.23". The tire’s rim width range specification tells us that it can be mounted on a 15" wheel of any width between 5.5" and 7.5", so after applying the 2/10"s rule of thumb we can find out the corresponding change in approximate section width of the tire.

2/10th of an inch doesn’t seem like much at first, but in this example the extreme range of width change is 8/10" which on some modified vehicles with aftermarket suspension and wider wheel and tire setups, can make the difference between clearing the fenders and suspension or rubbing over bumps.