I figure the blanket statements against it are for the herd. It can be done, but numerous things have to be right.
Firstly, in the herd mind, a 205/70 ST 14" and a 205/70R14 are identical, nothing to pick between them, apart from one says ST on it.... well the trailer one maybe has a 2000lb or so load rating and the car version maybe 1400lb. Also they don't see that trailer rims and auto rims have different bead profiles, auto tires fall off trailer rims.
Secondly in the herd mind. "If you blow it up to maximum sidewall it will blow up." No, that is the only point it attains it's maximum load rating. A tire HAS TO BE at sidewall to achieve it's max speed and load ratings, otherwise it's grinding sidewall heating up too much. Numbers on your car door pillar are as much about ride and road noise as being the maximum inflation pressure, they are a hard minimum though, look in the manual some cars will tell you, if driving at high speed or with heavy loads for long periods, inflate tires to max sidewall pressure.
Thirdly in the herd mind. Hot pressure = cold pressure, "it's all pressure, if I check at a brief stop and my pressure is 5psi up, I should let it out." I don't care if it's 50 PSI over cold, leave it, it's designed in.
These people need to be told, if it's a trailer put the correct trailer tire on it.
However,,,.
Load rating, load rating, load rating, auto tires only go on auto rims, trailer tires only go on trailer rims, run (whatever) tires on trailer at max sidewall cold pressure always, it runs coolest and supports the most.
Get a tire rated 20% over half the axle load rating at least, leaves room for Murphy,
Do not expect an auto tire rated high enough load to actually fit in the wheel well of your factory trailer. ST tires mostly have much higher load ratings for their size than P tires and as they get larger, LT tires even. Modifications to accommodate your preferred tire are on you.
Rims, auto tires, use auto rims, trailers often want a negative offset though, if a rim suitable to swap on your vehicle is high positive, then you may need to use spacers on the trailer, getting this right, modifying the hub, ensuring the bearing can take the load if the centerline of the combo is off, all on you.
However, the above is all fairly simple to achieve by offroaders who'll be doing an axle flip or lift on a trailer ensuring plenty of room that large tires go under it and are typically using trailers limited in weight and size. Then the TV matching LT tires in use often have decently high load ratings that you don't even have to notice to "get away with it."
Should you therefore decide to do this with your econobox Toyota and put matching tires on your teardrop you are likely to hit the following problems... i) Load rating, you've probably got ~800lb rated tires on your econobox, this limits you to a total weight, wet and loaded (GVWR) of 1300lb after you leave 20% margin (For blowouts etc, not for when you accidentally want to carry 20% more.) So if you built heavy, forget it. Secondly if your base trailer came with the little 8" rims, or 10" even, you've probably built everything in around them, there may not be room to stick a 24" diameter tire where a 20" or less diameter tire was meant to go, test clearance at full suspension articulation, buy new fenders, rehack your trailer body, whatever you have to do. Thirdly, rim offset, FWD positive, trailers likely negative. might not work, may require spacers, or different hubs if you've got 5x100 and trailer has 4x100.
But yeah, always use ST tires on trailers.
