Here was West Marines review it is a little contradictory in its wording.
Radial or bias ply tires?
Radial tires have plies that run perpendicularly across the tire and belts (often made of steel) running below the tread around the tire’s circumference. Bias ply tires have their plies running at 30° angles (like the stripes on a candy cane). Most motorists believe radials are better (and they are for your auto). Should you buy them for your trailer?
The answer depends on your trailer’s handling. Bias ply tires have stiffer sidewalls, so if your rig tends to sway, they may help reduce this problem. They also have advantages for carrying heavy loads. Radials, as most of us know, are vastly superior for tread wear. They’ll last an average of 40,000 miles vs. 12,000 for bias plies. However, oxidation, not tread wear, wears out trailer tires. Radial tires are also less prone to developing flat spots on one side when they are parked in the same position for weeks at a time, and tend to run cooler on long trips. Bottom line: consider your trailer’s handling and the manufacturer’s recommended tire type. If you travel long distances and/or put lots of miles on your tires every year, radials are worth the extra cost.
Each of your trailer’s tires should be the same type, size, and construction—do not mix bias-belted and radial tires. In selecting tires for your trailer, buy the size, type, and load range found on the trailer’s certification label or in the owner’s manual. Keep in mind that tires have a load rating that indicates the amount of weight they can carry safely. That includes toys, Igloo coolers and camping gear. Overloading can lead to a large heat buildup, causing accelerated wear or a blowout.
