I've got a pair of mobile-home axles under my trailer. 14.5" tires. I put them on 15 years ago. Greased the wheel bearings and put new DOT rated trailer tires on it. Never had a single issue with it since with 15 years of use. Granted I never carry more then 7000 lbs. Trailer weighs 2000 lbs. empty so it's hauled 9000 lbs. all over of the place with zero problems. I just came back from a 1200 mile haul (2400 mile round trip).
There is nothing wrong with those trailer axles. They just have smaller bearings then usual since they are built to carry a heavy load for short time and not the converse. When not loaded to the max they last a long time.
The doughnut 14.5" rims are rated 3500 lbs. each and each axle is rated for 7000 lbs. Axles have # 2580 Timken bearings.
Trailer axles have the same size axle stubs as regular trailers with 6 or 8 lug hubs and can be upgraded if wanted.