On trailer tires, run what ever the sidewall says is maximum pressure for the tire. The only reason we're running below rated pressure on the trike rears is for comfort. Out here in the desert where it's been 110 + for the last week -- well, yesterday was only 109 & today is down right chilly at 105, I've bumped my rear pressure up to 28 so the tires run cooler. When it cools off, I'll go back to 22 because the ride at 28 is pretty harsh.

NM