[wagonman76]

Actually, for the most part, trailer tires are designed much heavier than car tires. I honestly havent looked at the 12" tires, but for the 14" and up that I am familiar with, PSI rating is higher, and sidewalls are a LOT heavier. The 14" tires on my camper are rated at something like 1760 lbs each. Try to find a 14" car tire thatll hold that kind of weight. My old 900# trailer had the same tires and I didnt even know they had no pressure once because the stiff sidewalls kept their shape.

The reason for the bolt pattern is most trailers tend to use only a few bolt patterns. The very small ones are 4 bolt. Up to 3500 lb axle is usually 5 bolt 4 1/2" BC, same as Fords and Jeeps and some others.

Trailer tires really take a beating. First of all, the weight. And trailers rarely have shocks. And many trailers have brakes that will lock up so those forces are the same. Only thing different is the cornering forces, but the super heavy sidewalls should handle the forces of a car with no problem, compared to the wimpy sidewalls of passenger tires.

Trailer tires are also usually designed for higher speed operation, at least the smaller ones. Reason is it is turning much faster than the tire of the vehicle that is pulling it at highway speed.

I think they say "trailer use only" because then they dont have to be built to the same safety standards as those for cars.