In this Ag Tire Talk blog, James  Tuschner provides information comparing combine dual tires to super singles tires. 

Why are agricultural tires so difficult to find, why are prices increasing, how long will this continue, and what steps do you recommend producers take to make sure they have the tires they need?

Most rim widths are set by TRA standards and follow a rule for the overall width of the tire. But because IF and VF tires “squat” further and that outward pressure under loads puts more stress and “pull” on the bead areas, if and VF rim fitments are normally always one size larger — 1 to 2 inches — than a standard tire or the same width.