If you are having trouble locating a specific size trailer tire locally, you might try etrailer.com. I got new tires for my 1983 Cobra at a decent price and essentially free delivery. They probably have a wider range of sizes than any local dealer. I went ahead and got the "ST" trailer tires, but my hangar partner, airshow pilot Bob Carlton towed hundreds of thousands of miles with his jet Salto glider in a trailer equipped with normal, everyday radial car tires and never had a problem. But he always towed with a Dodge 2500 diesel pickup, so trailer sway was never an issue. If you tow with a smaller vehicle, get the ST trailer tires and pay attention to proper fore/aft loading and tire pressures.