The Basics of Tire Sizing

Tire sizing can be confusing at first but once you understand the different formats used for tire sizing it is easy to determine the sizing of our various flat free tires. Below we will walk through the different formats you may encounter when looking at tires. Note that the tire sizes found on tires will not match the Amerityre part numbers, so it is important to see our section on understanding Amerityre part numbers. Note also that the indicated tire sizes do not indicate the rim bead width, which must be measured separately.

Example 1: 4.10/3.50-4″

This type of nomenclature is used commonly with handtruck tires and wheelbarrow tires, as well as other material handling and lawn/garden tire applications. In this case the diameter of the tire is not mentioned, but can be calculated by adding the rim diameter and two times the distance from the outside edge of the tire to the edge of the rim. In our particular example, the wheel diameter is equal to 4.1 + (2*3.5) = 11.1 inches

4.10 = refers to the width of the tire, measured in inches

3.50 = refers to the distance from the outside edge of the tire to the outside edge of the rim, in inches

4″ = refers to the diameter of the rim, in inches

It should be noted that tire sizes in the industry are not exact. It is not unusual for tire dimensions to be slightly different than the tire markings. For example, a 4.80/4.00-8″ tire typically has a 15.5″ diameter rather than the 16″ diameter you would expect. However, it is considered an adequate replacement as it meets industry standards.

Example 2: 18 x 8.50 – 12″

Golf cart tires, lawn mower tires, and other lawn/garden tires are often marked in this manner. Other examples include 11 x 4.00 x-5″ and 9 x 3.50-4″ tires

18 = refers to the diameter of the tire, in inches

8.50 = refers to the width of the tire, in inches

12″ = refers to the diameter of the rim, in inches

Again, there may be some variation in sizes between the tire label and the actual tire size

Example 3: 26 x 2.00

Bike tires and some cart tires are marked with the above nomenclature.

26 = refers to the tire diameter, in inches

2.00 = refers to the tire width, in inches

Besides our bike tires, all semi-pneumatic tire sizes are written in this way. The overall tire size is typically written along the tire sidewall