Load the vehicle with everything you plan to travel with and then add full fuel and as much water in your fresh water tank as you feel you should need. Personally I travel with a full water tank.
Then get your coach weighed just to see if you have exceeded your axle weights for the front or the rear.
If you have not exceeded the axle weights, then inflate all of your tires to the maximum axle weight and you will be good to go whether you have a full tank of fuel or an empty tank, out of groceries or you just loaded up at Walmart, Summer wardrobe or Winter coats.
Getting the coach weighed and inflating to that weight is a certain way to insure that your tires will be overloaded in the future because the weight changes and shifts as you travel. You just need to weigh the coach to make sure that you are NOT overloaded on the axles.