I had a similar problem with our Scamp
5er. When we bought our Scamp
, it had been "lifted" so a pickup with higher side rails could pull it. Our truck has a lower bed and side rails, so we had it lowered and, at the same time, bought two new tires on 14" rims to replace the rather under-sized and over-loaded 13" wheels Scamp sold the trailer with.
Less than 10,000 miles later, one of the tires showed very significant wear on one outside edge, similar to what I saw in your picture, and needed to be replaced. Thinking our axle
must somehow gotten bent, I crawled under the trailer to inspect it, and got a surprise. It looked like our axle had been re-installed at a slight, but still noticeable angle to the frame.
I went back under with a framing square to confirm what I thought I saw. It looked like one side was welded on 3/4" forward of the other. I checked again with string, measuring the distance from the hitch to the forward-most edge of the axle-frame connection on either side. 3/4".
I took the trailer back to the RV shop and asked them to fix their mistake. They also paid for a replacement tire . . . and my gas mileage went back up to where it had been before we had the axle work done. (I'd attributed the drop in MPG to driving a pickup truck with 150,000 miles on it.)