The flexible tire sidewall enables a tire to be mounted on slightly wider or narrower wheels. This is the reason why each tire size has a rim width range on which the tire can be mounted.

Standard organizations, European Tire and Rim Technical Organization (ETRTO) and The Tire and Rim Association (TRA) established the rim width range for every tire size. If a rim is too narrow or too wide in relation to the tire width, performance of the tire is significantly reduced and the wheel or tire failure may occur.

Too wide rims improve handling but the ride is harsh because sidewalls do not bend enough on rough surfaces (over potholes and bumps). On the other side, too narrow rims may cause sidewall deformation when fast cornering. All these facts have to be taken into account when selecting adequate rims.

Standard organizations have also developed the measuring rim width for each tire size. The Measuring rim can be defined as the standardized rim width for a single tire size (also referred to as "the Measuring Rim", "the Design Rim Width", "the Design Rim", etc.). Due to this fact all tire manufacturers are capable to measure their tires on the same size rim. For example, all tire manufacturers measure tire 235/45R17 on a 8 inch wide rim.

When changing tires and/or wheels with wider or narrower ones, the information about appropriate rims for a single tire size can be found in tire manufacturer's rim conversion charts. There are several rim widths in these charts corresponding to a given tire size, but only one is shown in bold. These rim widths, or approved rims, marked in bold, refer to measuring rim widths. In other words, the term measuring rim refers to the wheel/rim width upon tire is measured.

You can use our Wheel/Rim Size Calculator which shows the acceptable wheel/rim width range for any given tyre size in accordance with the ETRTO standards and Databooks of the leading tyre manufacturers. It gives You the answer to the question "What rims fit my car?"

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