I run 20.5 x 10 tires and rim but it required a spacer to be installed on my trailer which came with 18" tires originally.
I am a firm believer in bigger is better and typically put on the load range E tires on trailers you end up paying more for the tires but my thought process is if a tire is rated for 1560lbs and you have two of them so (3120 LBS) and the total load is under one tires rateing you should not have any problems trailer tires are a pain in the *** to change on the side of the road. one other comment cover the lug nuts with grease at the beginning and end of every season just incase.
guess I should be more clear 20.5x8/10 . u know the wide small tires on most 2 place trailers.
not big 20 in ram truck tires.
looking to upgrade to some 12 or 13 in with alloys. more so I dont have to keep buying more rims and tires when the rim gets rusty after a yr or so and the bead starts to leak.
usually great tread but rim shot. then I find my self at the man mall buying a new tire.or worse last time I needed a spare the spare had lost its air because of rust on the bead.
could just be the cheep fleet farm china set up but the big trailer with alloys never has issues and the 12 ft clam has been a on going thing from yr 2