Hi Doug

My 3326King has Goodyear ST215/75/R14s on it. (tandem axles, of course).

Because of where the power-band is with my truck, I tend to tow at 70-75 mph when I use overdrive, which I do on all but the longest/steepest hills. Trailer, and tires, do great. No clearance issues. No cupping. No problems.

Hope that helps
Mack

P.S.  Don't forget to have whatever you get ballanced. A lot of people don't bother ballancing trailer tires. But, I'm sure, you know that.