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Section Width

A tire's section width, also known as cross section width, is the measurement of the tire's linear width from sidewall to sidewall (excluding any raised letters, ornamentation, or protective ribs). This is crucial when calculating the tire size because improper width, height and aspect ratio can affect steering response, traction and ride comfort. This is printed on the sidewall itself along with other markings that give you information about the tire.

Section Width


About Section Width

It's important to note that section width is not the overall width of the tire. Per industry standards, this measurement is done on an inflated tire (without any load applied) after it has been mounted on a proper wheel assembly. This can also be heavily influenced by the width of the wheel upon which the tire is mounted.

For example, the section width of a tire mounted on a narrow rim would be "narrower" than if the same tire were mounted on a wider rim. Because of this, there is a specific rim width range designated for every tire size. Tires should only be mounted on wheels within the tire manufacturer’s predetermined rim width range.

Factors like air pressure and load weight can affect the operating section width of a tire so it’s also important to understand that the section width is used for sizing purposes only.

Section Width on Metric Tires

If you are driving on a metric tire (a tire measured by metric sizes), the sidewall code will look something like this: 215/65/R17 99H. There are also P-metric tires which would read like this: P215/65/R17 99H. The first number set in the code indicates the section width of your tire. In both cases, the section width is 215 millimeters wide.

While both are the same size, there can be slight differences in their performance so it’s best to have all 4 tires of the same type. To learn more on the differences for each, take a look at our guide on Euro vs. P-metric Tires.

Section Width on High Flotation Tires

If your tires are high flotation tires (tires typically for light trucks), the sidewall code will look something like this: 31X10.50/R-15. In this scenario, the number set that represents the section width is not the first, but the second set, 10.50. High flotation tires are measured in inches, so the section width in this example is 10.5 inches.

For more information on sidewalls and various tire types, check out our guide here on reading a tire sidewall and flotation tires.

If you have any questions or require any assistance, stop by any of our Discount Tire locations and we'll get you taken care of!

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