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AG Tires: Basic Tractor Tires Size

Tractor tire sizes are indicated on the sidewall of the tire. Although all important information about the tire is clearly presented, it can be confusing. The sizes are often indicated using standard or metric formats, and are crucial when replacing the tires. Each of these formats needs to be read differently. The first step to look for is which format your tires use and then read the measurements according to that specific format. After learning the format the measurements can easily be converted to a different standard.

Standard Tractor Tire Size 

The standard tractor size is simpler to understand than metric tire sizing, as we in the USA are more familiar with inches than millimeters used in metric formats. The information is usually written as width x diameter. For example, a tire that is “16.9 – 30” has a 16.9 inch width and a 30-inch diameter. The diameter indicates that you will need a wheel that is 30 inches. Tires that have a “-” in their size, like the previous example, are bias-ply tires. Manufacturers will mark the size with an “R” instead if the tire is a radial-ply.

Metric Tractor Tire Size

Metric tire sizes are in millimeter measurements and are separated with a “/”. Metric sizes are often used in more modern tires. The first number represents the width of the tire, and the second number indicates the aspect ratio of the tire. There is also a third number that measures rim diameter, but this number is measured in inches rather than millimeters. For example: 380/70R24 indicates that the tire is 380 millimeters in width, with an aspect ratio of 70, and 24 inches in rim diameter. To find the sidewall height, simply multiply 70% of 380, which equals 266 millimeters. The R in the measurements will let you know that this is a Radial tire.

Rim Measurements

A complete wheel requires the tire and the rim together. A simple tip to remember when trying to find the rim width is to measure from inside the bed lip to the opposite bead lip. A common mistake is measuring the total width of the rim, which will not accurately reflect the true specifications of the tire. Oftentimes tire measurements indicate the rim measurements, and even in cases where it does not, manufacturers often print the rim size inside the bed fladge. The first number is the rim diameter and the second number is the rim width. If you still cannot find the exact rim measurements with either of the 2 formats discussed here, then you can measure it manually yourself using the tip above.


Still not sure how to best measure your tractor tires? Contact us at OTRUSA.COM, or give us a call at +1-855-687-8721! We have over 20 years of experience in the industry, and are happy to answer your questions and provide good quality tires to serve all your needs and maximize the performance of your vehicle.

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