Pop Beavers already stated several of the differences between LT and ST designated tires. According to spec sheets, ST tires are supposed to also have the below listed characteristics in addition to what Wayne said:
"ST" tires feature materials and construction to meet the higher load requirements and demands of trailering.
The polyester cords are bigger than they would be for a comparable "P" or "LT" tire.
The steel cords have a larger diameter and greater tensile strength to meet the additional load requirements.
"ST" tire rubber compounds contain more chemicals to resist weather and ozone cracking.
"ST" tires have stiffer sidewalls, and won't flex as much as a "P" or "LT" tires.
Okay, now we get back to the question. Would/should you use "ST" tires and not "LT" tires on trailers. This is a great question, with probably not a good answer.
If you look at Michelin, Hankook, and many other tire manufacturers websites.....they have LT tires that they recommend for trailers, and they don't even build a "ST" designated tire.......and that kinda makes me wonder if they are building some kind of crossbred ST/LT tire and that is the reason they are recommending it for LT and trailer uses. I would think that they sure wouldn't recommend a LT tire for a trailer, and take the risk of being sued, if they weren't confident in it being suited for what they recommended it for.
In our great tire experiment (the 14 inch Euro tires), we are currently using LT tires that actually have more load carrying capabilities than the ST tires that we replaced.......so the advantage of an ST tire in that scenario is void.
However in the 15 inch part of our experiment, we are finding ST tires that carry more load than any LT tire manufactured, so why not stay with a ST designated tire for 15 inch equipped trailers. More is always better.
Will these LT tires stand up over time to ozone cracking/weathering as opposed to the ST tires? If we replace the tires every 5 years as recommended for "ST" tires, then I would think a LT tire would be good for that long also......so that advantage of a ST tire might (and I only say might) be voided there too. If we go longer than 5 years, then that advantage might come more into play over a LT tire.
I am sure that this thread will get more responses, quoting internet sources/articles and I welcome them. I think that this is all part of our tire experiment too.
Bobby
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