I disagree, and am with Crewcheif. I only use trailer tires (And have never had a failure, like anything else, they need to be maintained, checked, armor-all'd, etc), and I trailer an hour at minimum, normally 3+ hours to get to water at freeway speeds (75MPH here in Arizona).
Reason being, car tires are designed to give better ride and control in many varying conditions, even at high speed such as the forces of accelerating and stopping, turning, etc. Trailer tires do not need most of this. What they need, and do, is much stronger sidewalls (You're gonna curb 'em far more often, and stress/tear up the sidewalls on tandems or triples particularly just cornering), and their "ply" construction and ratings are real because they are bias ply tires, and harder compounds to absorb more heat, and induce less wear and tear since they are usually quite a bit smaller in diameter than you're car/truck tires. THUS, they spin much faster and much more often per mile.
Trailer tires are typically 6 or 8 bias ply in light trailers. Radial tires are normally 2 ply plus a steel belt (not counted as an actual ply), and the "ply" rating on them is a "strength equivalent" abbacus computation to compare them directly to bias ply tires because the DOT requires it. Whether that number is accurate or not is not the point. If you doubt this, next time you replace your $600 each Heavy Duty 12 ply rated off road truck tires, cut one open with a sawzall. I think you'll be surprised. Load ratings are another thing that are completely different and you cannot directly compared between trailer tires and passenger car/light truck tires.
The biggest complaint, and legit, on trailer tires when they fail is because they just "flew apart". That's usually not the case. These tires RARELY wear out, on the tread side of things and besides looking at that, air pressure, and weather checking, noone pays any attention to them. There are date codes on these things (there's a website to tell you where and how to check that), and it's very common to find tires 5-10 years out of useable date. I have project boats here that I KNOW the tires on the trailers are original from as far back as 1976, still hold air, plenty of tread left, look decent, and I wouldn't tow them down the street to the Circle K. The rubber compounds degrade over time, through heat, UV light, alien intervention, whatever.
18 wheeled tractor trailers or any heavy truck still use bias ply, know why now?
Ray
PS, some reading for ya
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=219&
