My last trailer had 14" wheels, the current one has 15". With these two wheel sizes, the choices of tires with high load ratings and quality construction are very limited. The first thing to have to check to make sure the load rating of the wheel on you trailer can take the extra pressure of the higher pressure tires. After lots of research over the years, I think the best choices are:
Kumho 857 Trailer Tire http://www.tirerack.com/tires/tires....150516133245:s
which is a trailer tire that exceeds the "ST" standard.
The only other choice I could find in load range D was be the Kenda Karrier Karrier
. They used to make a load range D (65 psi) in size 215, but now they only off it in the 205 width, but it still has a couple of hundred pounds more capacity than the Load Range C 215's.
You have a few more choices in the 15" diameter. As mentioned, the Maaxis M8008 comes in load range E (80 psi) and is a very well respected tire. There are a few other manufacturers that offer a Load Range E ST tire, but Goodyear does not seem to be one of them.
Goodyear does make the Cargo G26 http://www.tirerack.com/tires/tires....5G26&tab=Sizes
which is rated for "all position" including trailers and comes in 225/70R15 size which usually fits instead of 225/75R15. This tire is sometimes used on the euro-style (think Sprinter) vans, and is made in Europe. It is a well respected tire on various RV forums and at 65 psi, has a capacity of 2,470 pounds.
With 16" wheels, the choices are much wider. There are several manufacturers - including Maaxis - that make 80 psi ST tires, plus there are LT tires available. You have to make sure you get an LT tire that is rated for trailer use. The most popular seems to be the Michelin XPS Rib XPS Rib tires | Michelin US
, but there are many others, and quite a few of them are not manufactured in China
Just my two cents .....