To answer your question ? 14.9X46 rims, But the Ertl tire does fit tight on them. Why do you want Ertl tire? Iam as posting a few pictures to help you and everyone else. Type's of Duals: One rim with two tires, some people call them Banded or Clamp on Style. Or More popular one's today are Axle Style: 2 pr. rims and hubs so you can adjust them to the row spacing you desire. You can also remove the outer tires if not needed then. Removeable Duals is what you guys have been calling them? When you purchase tires from us we include these spacers and axle rod for them. The Standi Tire Sizes match the real ones for the most part! So if the real tractor is using 20.8X42's then the 1/64 tractor will look simliar to it. They are scaled to the real tires. Example: 710X70X38 is a popular tire on the real tractors today. Real tire is 76" tall X 27.6" wide on 38" dia.rims. Standis 710X70X38 tire is also these measurements in 1/64 scale,1 3/16" tall X 7/16 wide on 19/32" dia. rim. Hope this helps every one ! Any other questions email us.