Here's some good info on tires as they may apply to trailers, culled from another site:

"I said I would report what response I got from Cooper Tires on the ST vs LT issue. Here goes. Cooper sent me an email with a phone number to call. The customer service rep at the number put me on hold and got a gentleman to talk to me who has years of experience actually building the tires and is a trailerist, also. Yes, there is a definite difference between Cooper LT and ST tires.

However, it is not a "safety" difference as long as the load rating is correct for your trailer's gross weight when towed. Both ST and LT tires can be safely used for trailers. The difference in construction is this: Cooper ST tires are basically a tire that combines passenger car tire construction techniques, with heavy duty truck tire fabric and cord materiels. This results in an ST tire having a high LT type load rating with the lower air pressure requirements and soft, shock absorbing sidewalls of a passenger tire. There is also extra UV inhibitors and oils added to the rubber to help in storage. This is much easier on the suspension and other components of the trailer on bumpy roads than the stiff sidewalls and higher air pressure of the LT tires. As far as tire safety is concerned, he stated that is up to the trailerist and how he maintains the tires, keeping the proper air pressure in the tires, and choosing the correct load rating. He stated LT tires have an advantage because of the larger choice of tread patterns and number of sizes available to choose from to suit the conditions you are towing in, such as snow, unimproved roads, etc.

He also stated that it is imperative to not allow the trailer to rest on the tires in the same spot for months at a time in the off-season. This causes the fabric cords in the tire to take on a flat "set" which can then cause some of them to actually break apart when you next take the trailer out on the highway. This can cause complete tire failure. He stated the best thing to do is to store the trailer on jacks with the tires in the air, or removed completely. This last information was of concern to me since I only have "stabilizing" jacks and cannot lift the trailer enough to take the load off the tires without serious effort. At any rate, that is what Cooper Tires has to say on this subject."

Thanks for the heads up Gary. It's always better knowing the exact reasons, why some items are better for a particular application, than the speculations that are often prevelant in the various discussions..

I find it interesting to note, that of the several brands of American brand LT tires I've owned over the years, none have dry rotted over their life spans, or had their cords damaged from unjacked, yearly seasonal storages of several months.

I also find it intriguing that Cooper mentions the "softer" ST sidewall construction. Many ST supporters have continually mentioned the extra stiff sidewall construction of ST tires, that supposedly contributes to better support, which is "necessary" for the trailers' high center of gravity. Yet in the same thread, LT tires are berated for having too soft a sidewall and are therefor not suitable for trailer installations.

It can be confusing, for a trailer owner to read the many conflicting reports, about the suitability of various tires. Obviously I take some of the "experts'" advice with some speculation, gleaned with real world experiences of myself and others having similar results.

Talking about small two horse bumper pull trailers here with 205/75x15's...

RTSmith, another reason most of these "ST" tires have a speed rating of 65 mph or less.... Not alot of material holding the tread to the bead.... I would rather have a name brand "P" rated tire that has the same load rating that the "ST" tire has. Most of the time you'll only step up in one width size. Most of those "P" rated tire have a speed rating of 99 mph or better. Think about a front wheel drive automobile and what it puts a front tire through. What did we use 40 years ago on these small two horse trailers before there were "ST" tires, 700x15's, F78x15's, G78x15's, etc...

So, where does all the "info" come from that "ST" tires have a stiffer sidewall when I can go out and flex the side wall of a "ST" tire with my knuckles with 50 psi in it?  They do seem to have a softer sidewall than a "P" rated tire. The P225/70R16 LTX MS Michelins on my Honda Element have 35 psi in them, they are alot stiffer than the "ST" tire on my two horse trailer that are set at 50 PSI... I bet that "ST" is somewhat lighter also if you were to weigh one compsred to a "P" rated tire of the same size.

Gary, I think we're in agreement.

I've seen good service from a ST225/75R15 tire in a ST, on a small trailer. I am always one to use a LT on the 16" models.

You bring up a good point on weight we've seen. Compare the weight of the hi-rated 16" Chinese tires versus the Goodyear G-614. A dramatic difference!