My (stock) Deuce rims are marked as suitable for up to 12:00x20 tires. I assume this applies to bias ply NDC/NDCC tires, don't know what is the max radial tire size. Maybe 12:00R20 or 14:00R20. Note that radials ending in .50 (i.e., 12.50R20) are generally SMALLER in diameter and wider than a comparable bias ply tire ending in :00 (in this example, a 12.50R20 would generally SMALLER in diameter and wider than a 12:00 bias ply tire by about 1/2 inch).
I have read of some people using up to a 15:50-80R20 on a stock Deuce rim, generally with less than fully satisfactory results. The 15:50 tires require some way to compress the bead to seat on a stock 7" wide rim, and often rub on the drag link during sharp right hand rims. That size tire is better suited to a 10" rim with the extra 3" added to the "bottom" of the dish, i.e. the lock ring side. This will prevent tire rub on the steering components, widen the track width, and, in super single configuration move the outer tire wall outward so the truck does not look so funky.
