Goodyear Tire and Rubber .... weighing RVs
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.
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and from Tireman9 (actual tire engineer) rvtiresafet.net tire blog tells us why max pressures are needed to help hold the tire together while side scrubbing around corners... (snipped for length)
**When not driving in a straight line there are special side loads on multi-axle trailers because the tires are fighting each other because they are not "pointed" to the center of the radius of the turn. These loads cause interior structural tearing. Sometimes 24% higher loads than those seen in tires on non-trailer application. Initially tearing is at the microscopic level but with time and repeated cycles these forces grow which can lead to small cracks at the belt edges.
You can lower these forces by either decreasing the load 24% on the tire (probably not something you want to do or may not be able to do) or you can increase the inflation to stiffen the structure and decrease the slip-angle. In this case you could increase the tire inflation from the minimum inflation needed for the static load to the inflation associated with the max tire load as molded on the tire sidewall.