Wondering which Ag tire size options will work on your equipment? Use the Rolling Circumference Index (RCI) Chart!
How It Works
Rolling Circumference Index Chart, or RCI Chart categorizes farm tires in accordance with overall diameter / rolling circumference along with section width / row spacing.
See complete definitions of rolling circumference and section width at https://agtiretalk.com/ag-tire-glossary/
RCI Group, within RCI Chart, is used to make changing tire widths easy, with all tires in same group maintaining virtually same overall diameter, displaying size options that will fit equipment along with application.
Below is Example of Group 46 Alternate Sizes:
As shown above, in Group 46 (73″ overall diameter):
- 20″ Rows use sizes 320/90R50 & 380/90R46
- 30″ Rows use sizes 420/80R46 & 480/80R42
- 38″ Rows use sizes 520/85R38
- Broad Acre or Flotation uses sizes 650/65R38 & 800/65R32.
Below is an example of an RCI Chart from Firestone:
*Please note manufacturer RCI Charts only contain tires sizes produced by that specific manufacturer. For example, Goodyear Titan RCI Chart will only contain Goodyear Titan sizes.
How to Summary
To determine alternate sizes for tractor, here’s what to do using Goodyear Titan’s RCI Chart shown below:
- Determine Original Equipment Size(s) (E.g. 380/90R46)
- Find Group Number for Front and Rear Axle on RCI chart (E.g. Group 46)
- Determine Application (E.g. Flotation)
- Follow Group Number Column Right until reaching Row Spacing or Application.
Why not give the RCI Index Chart a try?
It is important to note that some equipment cannot use all alternate sizes listed for a variety of reasons including space limitations, drivetrain limitations, and other factors.
All information is provided in this blog solely to provoke thought. All deductions made from information on this site must be confirmed by Certified Ag Tire Dealer before use. Ag Tire Talk does not recommend anyone conduct tire service work with exception of Certified Ag Tire Dealer Professionals.