The OP profile shows a 322 FKS TT so most likely his OEM tire size is a ST225/75-15 D load range at 2540 lbs per tire.
Maxxis LT U-168 is a commercial grade tire. The 225/75R-15C D load range at 2469 lbs capacity. This is a euro all position commercial application tire designation and have became popular with all types of trailer owners in the US. Maxxis tires are very hard to find in many areas. Many folks have tire issues on the road have to settle for another china made ST replacement till they get back home.
I always upgrade from a ST tire to a 16" LT on my RV and non RV trailers. My current 11200 lb rv came oem with st225/75-15 D at 2540 lbs capacity and 28.3" diameter.
The LT225/75-16 E at 2680 lbs capacity and is 29.2" diameter is a popular replacement. Lots of brand choices with some type of hiway rib pattern work best for a trailer tire.
If you have room under the wheel wells the bigger LT235/85-16 E at 3042 lb capacity and is 31.5" to 32" diameter works great also.