An easy way to check:
- Lift and support that side of the trailer, do not lift under the axles
- grab the top and bottom (12 and 6 o'clock) of the worn tire and try to rock top to bottom
- grab the front and back (9 and 3 o'clock) try to rock left to right.
If no noticeable movement, it may be a bent spindle/axle.
If it moves noticeably, bad bearing.
Another method would be to check with a straightedge and ruler. Check the top and bottom of the "good" wheel on that side and compare with the bad wheel. This is not fool proof as the axles can be adjusted individually.
2011 Silverado CC/SB
2014 Cougar 31SQB