Wanting to change from STs to LTs..........

Michelin publishes a guide of tire pressures based on tire load. (This is linked somewhere else in this thread.) At the loading I will be placing on these tires, I will likely run 50-55 PSI.

IMO not the best idea for tire pressures on a trailer with 80 psi tires. Works great on other RV types.

Experienced trailer owners and many tire experts and our oldest trailer tire makers that understand trailer tire (P/ST or LT) issues use or recommend max sidewall pressures.
Now if the trailer owner has over tired the trailer above say 15-20 reserve percent above axle ratings then at some point max pressures isn't the best idea.

Tireman9 .....one of our tire engineers also recommends max sidewall pressures says; from rvtiresafety.com his online tire blog;

"The manufacturers do not take into consideration the side to side unbalance, as to do so would require them to provide larger (more expensive) tires. The other thing RV industry does not take into consideration is the forces to the tire structure due to running close axle spacing. Engineering analysis shows that when turning corners the forces trying to tear the tire apart can be over 20% higher in multi-axle applications than with tires at the corners of the vehicle.
The only options for the trailer owner are to up-size the tires (if there is room) or up-rate and increase inflation (if a higher Load Range tire and stronger wheels are available). Lacking the above being sure to run the tire at the inflation shown on the sidewall (i.e. max) will slightly decrease but not eliminate the overload forces.
...................................................................

RVsafety.com says;
Travel Trailer/ 5th Wheel owners Due to the severe use conditions experienced by tires when axles are very close together – tire industry experts recommend maximum (sidewall) inflation pressure for towable tires unless this causes a severe over-inflation situation (20psi+), often referred to as the ‘basketball effect’. If this is your situation allow a 10 – 15psi safety margin above the minimum required inflation pressure.
...................................................................

Goodyear website weighing a RV says this;
Special Considerations
Unless trying to resolve poor ride quality problems with an RV trailer, it is recommended that trailer tires be inflated to the pressure indicated on the sidewall of the tire. Trailer tires experience significant lateral (side-to-side) loads due to vehicle sway from uneven roads or passing vehicles. Using the inflation pressure engraved on the sidewall will provide optimum load carrying capacity and minimize heat build-up.

Sorry for the long post but when it comes to best tire pressure for tires on a trailer its important to use the best pressure for best long term reliability.