I assume it came with ST235/80R16E maypops. The new Goodyear Endurance ST is a good choice. Given the 14080 GVWR, the Sailun S637 might we an overkill. They are however a really good tire for the money. You would only need about 85-90 inflation for your load. If you inflated them to 110 pounds they would beat the trailer to death.
Fully loaded you will have less that 12K on the axles. A steel ply carcass tire like the S637 will add to towing stability and have a low rolling resistance.
Here is information on warranty and claims.
https://lionsheadtireandwheel.com/media/uploads/0/952_2015-Warranty-Claim-Form-Update-pdf.pdf