You mean the width of the rim? Going to 14 I wasnt sure if they would rub the fender or touch each other. Just didnt want to buy them and it not work. I emailed the trailer company a few weeks ago but never heard back
Went with Carlisle HD radials when replaced my tires - came in the same odd 185/80/13 size and the "HD" version had comparable load rating for the radial (otherwise seem to run lower). They look larger radius / less clearance in fenders, would have a real good look if want to increase overall diameter (dont need to in order to go radial).
I use a laser thermometer at stops to check rotor / bearing / tire temps at stops when towing, the radials run a lot cooler than the bias ply did. Cannot otherwise not notice a difference in handling (with a full size truck).