...
One reason for not going faster with ST tires is that they have less stopping power. They are too small. The reason they are too small is that originally all low-rider flatbed trailers (automobile type) evolved with small tires so that the fender is low, and the doors can be opened on the auto when it is on the trailer, or low over-tire flatbeds in general were desirable. All early travel trailers (2 steps) made good use of these small tires by allowing less fender under the interior cabinets, and therefore more storage space. The tires are especially designed to be small, yet carry heavy weights, just the opposite of truck tires which have evolved exceptionally larger as load capacity rises. Newer RVs tend to sit higher (3 steps+), making the necessity of small diameter ST tires obsolete.
The stopping ability is also reduced on ST tires because they are small, and, weight being equal, the rubber contact patch determines traction (friction) in the world of tires. Rubber tire friction (traction) does not rise linearly with added weight as it does in normal science. This non-linear principle does go against normal "area-of-contact/weight = an-identical-friction-coefficient" in physics, but it is an exception here. Race cars use wider, flatter tires to their advantage because of this exception. This also means that stopping traction may be decreased by reducing contact patch by over inflating the tires to theoretically increase load capacity.
The stopping ability is reduced on ST tires furthermore, because they are not designed with significant forward/reverse traction sipes. On dry, sticky roads, the sipes are not too important (as in drag slicks work under these conditions also). But the drag slicks also have significantly stickier rubber while ST trailer tires have a very hard compound. ST tires are more like aircraft tires than automobile tires. Not having sipes actually allows them to roll slightly cooler than LT tires as an example. Of course one can, and should, certainly oversize the LT tires to make up for this potential heat gain. And LT tires will give better stopping ability, if the TT brakes are upgraded to larger drums or disc for instance.
Trailer tires are designed to have side-to-side (lateral) traction because that is what they do. Travel trailers experience this to a much greater extent than the tow vehicles because of their huge side profile in side-winds. Except in calm, perfect frontal or tail-winds, travel trailers are constantly running at an angle to the tow vehicle which generates a lot of heat in the tires. Travel Trailers are literally like boxkites on wheels. So beware side-winds combined with high ambient temps.
I think the assumption has been that compact ST tires are adequate for trailers that were at one time towed slowly... before we went crazy with HP. I know, I like HP too. Then on the other hand, the indiscriminent use of fossil fuels is probably coming to a close soon. So small ST tires may again fill the bill in the future.
Wes
...
