Ag Tire Size Options:  RCI Chart

Ag Tire Size Options: RCI Chart

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

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:

Group 46 A Full Detail

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.

RCI Chart

Below is an example of an RCI Chart from Goodyear Titan:

Goodyear Titan Ag Tire RCI Chart

*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:

  1. Determine Original Equipment Size(s) (E.g. 380/90R46)
  2. Find Group Number for Front and Rear Axle on RCI chart (E.g. Group 46)
  3. Determine Application (E.g. Flotation)
  4. Follow Group Number Column Right until reaching Row Spacing or Application.RCI Chart Group 46 Snip with Circled Detail

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.

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10 Responses to “Ag Tire Size Options: RCI Chart”

  1. Stuart Reithemeyer says:

    I have a spray coupe with rear duals 340/85R24. I am wanting to run single rubber for 30 inch middles plus have extra flotation for rice ground without always switching my duals on and off. Will a 380/85R24 fit on the same rim?

    • James Tuschner James Tuschner says:

      Could you please provide year and model number of your Spra-Coupe?

      I would like to research further with specifics.

      Thank You

  2. Bryan M says:

    On a Magnum 340 RT with 21 inch tracks can you put a 520 85 R38 on the front

  3. Ray Bauder says:

    I have a JD 750, 20yrs old with turf tires on it that need replaced. Fronts are 25 x 8.50-14
    Rears are 13.6 x 16 with calcium. Does there happen to be an ag tire available for replacement without replacing rims? Thanks for any help on this matter.

    Atoned4, Ray

    • James Tuschner James Tuschner says:

      Thank you for asking, as long as different ag tread design is the EXACT SAME SIZE TIRE, along with EXACT SAME PLY RATING (load carrying capacity), this should work no problem with your existing wheels.
      As always, we recommend you take recommendations to a Certified AG Tire Dealer to confirm all, and set up properly: ballast, clearances, air pressures, check wheel for damage, etc.

  4. Jack K says:

    we have a 1987 CIH 7120 with 13.6R28 on the FWA front and 18.4R38 on the rear. We are going down to 20 inch rows. Which front and rear would you put on?

    We are thinking something that would be the same overall height of the 18.4R38

    Which one R50 or R46

    Thanks Jack

    • James Tuschner James Tuschner says:

      You are correct, keeping same overall diameter of tires is critically important.
      I reviewed the RCI Charts. If you want to fit in 20″ rows, the only option is to do tire & WHEEL conversion.
      Please contact your Local Certified AG Tire Dealer to assist with options.
      Thank You,

  5. louis peterson says:

    I am currently ruunning a 18.4 x 30 rear and a 12.4 x 24 front (bias) on a NH TL100. I want to go to a 380/85R24 radial (front) and possibly a 480/70R34. (rear). Will this combo work on my TL100?

    • James Tuschner James Tuschner says:

      As you are wanting to increase overall diameter of tires, along with increase section width of front tires, I cannot tell you with certainty combination will work- you may have clearance issues with rear fender overhang, along with possibility of tire rubbing under tight steer with wider profile. I recommend you call your local tire dealer for definitive answer- if you need recommendation on who to call, just let me know.
      Thank you for comment,

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