Tire Rack.com

Tire Specs Explained: Section Width

Lea esta página en español

Section Width

A tire's section width (also called "cross section width") is the measurement of the tire's width from its inner sidewall to its outer sidewall (excluding any protective ribs, decorations or raised letters) at the widest point. This measurement is made without any load placed upon the tire and after the tire has been properly mounted on its industry assigned measuring rim and has been inflated and reset to its test pressure after 24 hours.

Because a tire's section width is influenced by the width of the rim upon which the tire is mounted, the correct industry assigned measuring rim width for the tire size being measured must be used.

The width of a tire mounted on a narrow rim would be "narrower" than if the same tire was mounted on a wide rim. NOTE: because the overall diameter of a steel belted radial is determined by the steel belts, there is little, if any, change to the overall diameter of the tire due to differences in rim width.

The industry rule of thumb is that for every 1/2" change in rim width, the tire's section width will correspondingly change by approximately 2/10".

For example: a tire in the P205/60R15 size is measured on a 6.0" wide wheel and this size tire has an approved rim width range from 5.5" to 7.5" wide. The tire has a section width of 8.23" (209mm) when mounted on a 6.0" wide wheel. If that tire were mounted on all of the rims within its approved range, the tire's approximate section width would change as follows:

Difference from
Measuring Rim
Approximate Tire
Section Width
0.5" narrower5.5"8.03"
Measuring Rim6.0"8.23"
0.5" wider6.5"8.43"
1.0" wider7.0"8.63"
1.5" wider7.5"8.93"

Because of the different wheel widths used in the above example, there is a 9/10" projected difference in tire section width when comparing a tire mounted on the narrowest rim to the widest rim within its range. This may affect fenderwell and frame clearances when selecting optional aftermarket wheel and tire packages.

Most Popular Links

Air Pressure - Correct, Underinflated and Overinflated
Air Pressure vs. Dry Performance
Air Pressure vs. Wet Performance
Air Pressure, Temperature Fluctuations
Air Pressure/Load Adjustment for High Speed Driving
Air Pressure: When and How to Set
Breaking In Your Tires
Calculating Tire Dimensions
Checking Tire Inflation Pressure
Determining the Age of a Tire
Diameter Comparison of Light Truck Tire Sizes
How Do I Compare Price vs. Value?
How to Read Speed Rating, Load Index & Service Descriptions
Load Range/Ply Rating Identification
Match Mounting to Enhance Tire & Wheel Uniformity
Load Reduction of Euro- and P-Metric Tires on Light Trucks
Measuring Tire Tread Depth with a Coin
Mounting and Balancing
P-Metric and Euro Metric Tire Sizing
Run-Flat Tires
Selecting the Right Tires
Sidewall Markings
Specific Mileage Warranties
The Plus Concept
Tire & Wheel Owner's Manual
Tire & Wheel Package Installation Instructions
Tire & Wheel Package Ride Uniformity Confirmation
Tire Pressure Monitoring Systems
Tire Rotation
Tire Size Conversion Chart
Tire Size Information
Tire Warranties
Uniform Tire Quality Grade (UTQG) Standards
Where to Install New Pairs of Tires?


Want to stay on the inside track?
Sign up for our emails today!