I have the Trailex/Hobie Double trailer. The tires are a very small 4.80x8 on an 8x3.75 rim. The tire is both very narrow and of small diameter (about 16”). I get only about 5000-7500 miles of tread life out of them before they get to where I don’t really want to use them any more. I know from the forums some folks have switched to larger tires on 12” rims with a diameter of 20-22” depending on tire width chosen. These would likely rub the fenders on bumps and would significantly increase tire/rim weight and loading height.
I wanted a combination that would yield 18 or 19 inches in diameter. Ten inch rims would seem the obvious solution but they and DOT tires for them are quite rare. So instead I went with a slighter wider 5.70x8 tires on the same rims. This yields a diameter of about 18.5 inches. I should get a few more miles out of them and they also provide better flotation in sand.
Here’s a photo of the two tires side-by-side and a photo of my new Easy Lift Trailer Jack in action (which worked perfectly).
Peter