Understanding Tractor Tire Sizes

It is straight-forward to look for the number on the sidewall of your tire when searching for your tractor tire size. Understanding tractor tire sizes, however, requires breaking down the jargon on your sidewall. Tractor tire sizes are indicated using both standard and metric formats. The indications on your sidewall matter replacing your tires, and also when inquiring about the amount of beet juice tire ballast needed for your specific tire size. We get inquiries for the amount of ballast needed for countless tire sizes. As a result, we have been conducting research to obtain a better understanding of tractor tire sizes and thought it would be helpful to share the information we have found with you.

Standard

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Standard tire sizes are the easier of the two measurements to read. An example is “16.9 – 30”. Here, “16.9” indicates the width of the tire in inches and “30” indicates the tire will fit a wheel that is 30 inches in diameter. The “-” indicates the tire is bias-ply design. A standard tire size replacing the “-” with an “R” indicates the tire is radial design. To clarify, radial and bias-ply designs will be explained later on. Some standard sizes include the tire width. An example of what this would look like is “27 x 8.5 – 15” with “8.5” indicating the width of the tire in inches.

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Metric

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Next, is the metric format. Sizes like “380/70R24” are metric and found on most modern tires. Firstly, “380” indicates the width of the tire in mm. Secondly, the “70” indicates the Aspect Ratio of the tire. Width multiplied by aspect ratio gives sidewall height, so (380 x 70% = 266). Therefore, sidewall height of this tire is 266mm. “R” means the tire is radial. Lastly, “24” is the rim diameter in inches.

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Radial

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Tire sizes containing “R” are radial. Radial tires contain an embedded structure around the circumference of the tire. Radial treads flex independently from the sidewall. Therefore, allowing for more traction, even tread wear, and less of a footprint left in the field.

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Bias-Ply

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Tire sizes containing “-” are bias-ply. Bias ply tires contain multiple overlapping layers at an angle of 30-45 degrees to the tread line. Bias ply tires are stiff, so they are less prone to puncture when navigating over rough ground.

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Load Index

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Load index is a method to report load carrying capacity of a tire relative to its speed rating. In our example “125” is the load index rating. So, “125” means there is a capacity of 3640 pounds. Check out more load index values here Load Index Chart

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Speed Index

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Speed index indicates the speed a tire can travel when carrying a particular load. In reference to our example, the speed index is “A8” meaning the maximum speed it’s designed to run is 25 MPH. See the full list of values on our Speed Index Chart

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Tread Style

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Different jobs call for different styles of tread. Whether you are using your tractor for mowing or pulling implements in the field, there are various tread styles to help yield the best results. The tread style in our sample reference, “R1”, is arguably the most popular. These treads are versatile and perform well in mud, dirt and fields. View an expanded list of the most popular tread styles in agriculture Tractor Tread Style Chart

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Wrap-Up

We hope this helps you decode the jargon on your sidewall. If there are any areas we are missing, feel free to let us know! Our goal with this research is to determine how much beet juice is needed to fill every tire. Interested in inquiring about our beet juice tire ballast? We can help you find your nearest dealer by filling out the form on our webpage, or by emailing info@rimguardsolutions.com

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