A 12500 gvwr trailer can have a 2500 lb pin weight = 10000 lbs on the axles......or 2500 lbs per tire.
Now ad a good 15 percent reserve capacity and your trailer may need a tire with around 2800 lbs.
The market is wide open in the LT235/85-16 E at 3042 lbs capacity.
At the top of the chain is the commercial class all steel ply carcass tire;
Bridgestone R-250
Michelin XPS Ribs.
Next down is the poly tire carcass in the same LT size;
Other LT tires mentioned
Firestone Transforce HT
Cooper Discoverer HT-3
Goodyear Wrangler HT
ST tires ?? The only ST E tires I've seen on rv and non rv trailering forums with no complaints is the Provider ST tire.
New gen ST tires just out the last year or so are the;
Carlisle HD
Goodyear Endurance
Maxxis ?? Popular on some rv webs with Lots of complaints
You sure don't need a ST load G tire 14 ply rated at 4080 lbs capacity on that size trailer that may have 5.2k or light loaded 6k axles.
"good judgment comes from experience, and a lot of that comes from bad judgment" ............ Will Rogers
'03 2500 QC Dodge/Cummins HO 3.73 6 speed manual Jacobs Westach
'97 Park Avanue 28' 5er 11200 two slides