My trailer has ST 225/75R15 Load range D tires. From what I find on the web these tires should run at 65 PSI. However a label from Forest River attached to the trailer reads these tires should run at ...
The tire has no clue as to the weight of your trailer and max tire pressure is just that, max for the tire. Weigh the trailer and use that to find the right PSI. I bet the sticker on the TT is close.