Since 1903, all tires, tubes, valves, and rims have followed standards established by the Tire & Rim Association of America (T&RA). Such a move benefits manufacturers, farmers, and growers in the way they source tires and fit their equipment.
The European market would also follow this model, with the European Tyre and Rim Technical Organization’s (ERTRO) creation in the 1960s. ERTRO standardized pneumatic tires and rims in the same way as the T&RA, providing a benchmark for the industries to follow.
Each size that manufacturers develop must fall within the following tolerance for any given tire size in millimeters or inches:
- Tire Overall Diameter (O.D.) = + / – 2% versus the Industry Size Standard
- Tire Section Width (S.W.) = + / – 4% versus the Industry Size Standard
In addition to the above design limits, there are other considerations that affect tire design and construction. For example, tire dimensions can change simply from the tire’s type and construction whether standard, IF, or VF. Other design challenges and considerations include:
Tread Depth
- The tire tread depth based on the lug design affects the overall diameter (OD) of a standard R-1 pattern versus the same sized tire with deeper R-1W, or R-2 tread depth.
- Tire tread depth will also differ from manufacturer to manufacturer which will affect the tire geometry despite tires being of the same size and within the above industry tolerances.
Tire Weight
- In addition, tire weight is not mandated in the standard beyond the above dimensional requirements, therefore the type of tire or materials used will affect the deflection and geometry of the tire under load.
Tire Inflation
- Specifically, in bias ply tires, the different ply rating or load ratings of the same size can result in different inflated overall diameter (OD) based on a given air pressure/tire load.
- Radial tires with a steel belt package or belts may have different inflated OD from the same size tire with nylon breakers.
Construction and Design
- Lug design can also influence how the tire under load compares to the industry standard when fully inflated.
- Bead and sidewall optimization by each manufacturer can impact the type and width of the rim recommended that could deviate from the industry standard as an alternative rim fitment.
Using MAXAM’s very own AgriXtra85 VF tire, let’s look at how the tire compares with the organization’s standard:
| Tire Size | Outside Diameter | Section Width | Tread Depth | Design Rim |
Alternative Rims | |||
| (mm) | (in) | (mm) | (in) | (mm) | (32nds) | |||
| VF480/80R50 | 2038 | 80.2 | 479 | 18.9 | TBD | TBD | 16.00 | DW16A |
| T&RA Standard | 2038 | 80.2 | 479 | 18.9 | 41 | 59 | 16.00 | DW16 |
| ETRTO Standard | 2038 | 80.2 | 479 | 18.9 | – | – | 16.00 | DW16L |
Common Problems from Mismatched Tires
In agriculture, the application and operation most affects tire design and performance within the industry standards. As agricultural tires are considered “off-road” and not US Department of Transportation (DOT) regulated, there is some flexibility in the design process for each tire manufacturer to enhance features to deliver improved performance.
In all instances, the type of machinery, soil conditions, application, and air pressure maintenance will have a direct impact on its performance even after improvements. Here’s some things to keep in mind when using tires from different manufacturers:
| Tire Operational Condition | Tire Issue | Recommended Action |
| Tire Slip | Different brand tires on the same axle can create increased tire slip due to diameter or tread width differences when inflated and under load. | Maintain the same brand and size tires on the same axle or side by side to maximize the best possible traction and tire footprint, ensuring improved tire slip. |
| Excessive Tire Wear | Tire wear for more than 10% difference in tread depth or overall diameter (OD) on the same axle can result in a loss of traction, increased slip, increased fuel consumption, or can impact gear ratios. | We suggest replacing the tires on the axle of the same brand and OD. |
| Diameter and Width Differences | Tires that have more than 5% difference in overall diameter that are operating side by side or on the same axle can lead to a loss of traction, increased slip, gear ratio issues, and increased soil compaction. | Tire diameters need to be as closely matched as possible to prevent excessive tire slip and to limit any gear ratio issues. We suggest replacing tires on an axle at the same time with the same brand of tires to limit this occurrence. |
To get the best from your tires, understand that these small changes in tire manufacturers can affect the performance of your farm equipment. When you match up your Ag tires properly, you reduce the chances of tire slip, improve fuel efficiency, reduce tire wear, and minimize soil compaction. Check out our website to learn more about our lineup of radial agriculture tires or jump into some more learning on the best ways to choose an Agriculture tire.
