Going over the numbers, our trailer's gross weight is 7685 lbs. With 4 tires under this trailer, this says the load is expected to be 1921 lbs per tire. The difference between the dry weight of 5715 lbs and the gross weight of 7685 is 1970 lbs. This is cargo weight, thus the allowable weight for any and everything added to the trailer. Such as battery, 2 x LP tanks, chairs, folding table, portable grill, leveling blocks, chocks, toolbox, and all the "stuff" we carry in the trailer.
The original tires were load C rated, thus a maximum 1600 lbs at 55 PSI. Clearly, the original tires WERE NOT rated to carry the maximum load of the trailer!
The new tires are load D rated. Per the manufactures data, they are rated for 2040 lbs at 65 PSI. That provides about 8160 lbs of total tire weight rating.
A point to note, changing to higher load-rated tires DOES NOT increase the maximum load rating of the trailer. That is defined by the axle rating used for the trailer. A pair of 4000 lb axles can safely carry 8000 lbs, regardless of the tire ratings.
Please check your trailer's gross weight rating and your tire's maximum load rating. Overloading tires are a sure formula for major issues. And as the tire manufacturer states for ST style trailer tires, always cold inflate to the maximum pressure to carry the maximum load.
Tire wear, surface contact, and ride are not as important as proper weight rating and inflation. If the tires are the correct size, weight rating, and inflation, none of the issues of tire wear, surface contact, or ride will be affected.
If you have had tire failure at any time, you best look at the numbers. Overloaded tires and under-inflated tires are the major cause of tire failure. Tires over 5 years old from the date of tire manufacturer are subject to dry rot and should be replaced regardless of appearance.
Remember, the strength of a chain is defined by its weakest link.