Learned a good trick from another RV group. If you are using tires
that can have their pressures adjusted to suit a load or load range (actually any tire can do this, but typically only ST and LT tires
have load tables with more than one pressure) and if you are using tires
that may be rated higher than you need (typically this would happen when you replace your original tires with a higher Load Range, such as LR B's replaced with LR C's), how do you know you have the right pressure for your load without a lot of fussing at the scales? (Umm, the presumption here is that you have indeed already done some fussing at the scales to get your load and balances right...).
Simple suggestion -- Take the trailer, or truck for that matter, to a piece of nice, flat, pavement and mark a chalk line across the tires in question. Rotate the tires a couple of times and then look at the lines. If they are erased in the middle but still there on the outsides, the pressure is high. If erased on the outsides but still there in the middle, the pressure is too low. If evenly erased, the pressure is just right.
Be sure to actually measure the final pressure and compare it to your tire manufacturer's Load/Inflation Charts to ensure that it is in the right ballpark.