Like others have said, I think age/rot and lack of attention is the downfall to most trailer tires. Under inflation and maybe wrong load ratings. They end up sitting more the turning.
My 61 has 8" tires on it and they look old. I will definitely leave them on until that one is ready to be used, then I think they'll go. Snowmobile trailer has 8's
My 67 163 has 13" Goodyears. Something like Silver Streak II's They were on it when I got it.
14" Generals Altimax RT's that I just put on the 175 but I went to 14" on that so I could use the wheels I picked up off Craigslist. They are "car ties" but rated for 1653 lbs each. That is why I choose those. Got them from Tire Rack. They have about 80 feet on them. In and out of the garage once to twice.
I was just talking to someone this week about Goodyear Marathons and the quality issues. Generally Goodyears are overpriced party because you are paying for their name. My opinion. They all make some good and some junk. I've had good Dunlops in the past and bad. Same with Bridgestones. I have leaned more towards BF Goodrich over the last few years. Got a solid 60K out of my first set of Continentals on my Jetta so thats what I put on again. Ok not a trailer.