One advantage we have as RVers is that we tow with pretty much the same weights and loads every time, and this allows us to cut things a bit closer than the people at U-haul, for example, where every rental from every customer is different. It's very important to know where we stand so that we can learn how to compensate for and take best advantage of our towing capacities.
Please make the effort to stop by a truck scale to get the real numbers that can tell you if your WDH is adjusted right and what is really going on with the way you load your vehicle. I've learned something important every time I've made the effort to weigh.
1) This site will tell you where a lot of them are and how to use them:
http://catscale.com/
2) Do 3 weighings (the Cat Scale people charge $9 for the first weighing and $1 each for the others, at the time I write this):
1 - Hitched just as you rolled off the highway, with each axle on a different scale segment so that you will get 3 axle weights on the weigh ticket
2 - Repeat, with the WDH chains slacked
3 - Go park the trailer on the side somewhere, and then come back for just the TV axles.
3) The math:
The trailer axle is from the second one, with the slacked chains. The trailer tongue is the TV total with the slacked chains vs the TV by itself. The trailer total is the axle weight plus the tongue weight.
The gross combined weight is on the tickets from #1 and #2 above. This should be the same unless somebody got in or out of the tow vehicle (errors between these would tell you something about scale accuracy).
4) The thinking part:
-The first weighing series is reality for the way you are towing.
-Loads need to be managed.
-You don't want overloaded axles. Gross Axle Weight Ratings are on the driver side door placard and the trailer placard.
-You don't want an
underloaded front axle, because that's where your steering and most of the TV braking happens.
-You can distribute loads by physically moving them, removing them, or with the WDH. The WDH is a recommendation for all and mandatory for most, but especially important for people towing with lighter tow vehicles where we always need to use our capacity well.
-One painless and easy way to reduce RV weight is to travel with empty tanks, filling FW only when you are close to where you are going and opening the FW drain valve and dumping the gray water soon after you leave the campsite.