Tire issue

Found tire on trailer low on air,went to check it out, thinking nail in it, and found inside of tire with outer rubber ripped open, and still holding some air. Did not notice any problems on road, as I always check hold straps, tires, ect on gas stops. Must have hit something in road or pot hole.
Could have happened sitting on drive after the trip. Anyone ever have this happen ?
Current Tires are 4.80x12. Load range C rated at 990 lbs loading. Two years old, and that is also date code, not dry rot from bubbas discount house. Approx 1200 miles on tires. Thinking of going to load range E for a safety buffer.
Trailer have two pwc's and is loaded to approx 1800lbs. Any thoughts of suggestions on going to next tire range.

Thanks

Re: Tire issue

Tire max load 1980 lb Your weight 1,800. Does that include the trailer itself and fuel, gear etc. You are close to the limit and there is no reason not to get a better load rating on your next tires.