I bought a set of the 14" Kenda Karrier's Load Range D tires for our previous trailer because, as in your case, the Load Range C's that came with the trailer were just marginal capacity. The only 14 inchers Load Range D's I could find were the Kendra's (which are marketed by Martin Wheel and I got from Northern Tool
Kenda Karrier) and the
Kumho Radial 857 from Tire Rack that were out of stock, so I ended up with the Kenda's.
That being said, they were good, heavy tires and ran well for the 15,000 miles over 3 years before we traded the trailer ...