The easiest way to accomplish a proper weighing at a truck stop is:
1. Find a truck stop nearby, one with scales that have 3 pads
2. Drive on the scales with the trailer hooked up, but no weight distribution hitch engaged. Put the truck front wheels on the first pad, the truck rear wheels on the second pad, the trailer wheels on the 3rd pad. Then you have to hit the button and yell at the clerk (the button can be hard to reach because it's high up so the truck drivers don't have to lean down to use it). They'll ask for a truck number, just make one up (I use 69 because that's my favorite number).
3. Pull off the scales and unhook the trailer.
4. Take the truck itself over the scales using the same spot as before (front wheels on first pad, back wheels on second pad). Press the button and tell them it is a re-weigh for truck # (whatever you picked). Costs less for a re-weigh.
If this is a travel trailer, you can add a step:
3.5. While on the scales (or pull off if the scales are busy), hook up the WDH and ask for a re-weigh. This will tell you how well your WDH is working.
Lots of great data from this technique. Hitch weight is quickly determined:
TOTAL weight truck (both axles) with trailer and no WDH (this is important)
- TOTAL weight of truck (both axles) without trailer
= hitch weight
If you only use the rear axle weight, you will calculate an inaccurate hitch weight. If you use the weight with the WDH engaged, you will get an inaccurate hitch weight. A lot of folks misunderstand hitch weight and think that reducing the apparent hitch weight by engaging the WDH reduces the actual hitch weight the hitch sees. Not so. Hitch weight is hitch weight. Ditributing it is a good thing, but does not change the rating of your hitch. If your hitch is rated for 1,000 lbs with a WDH, that does NOT mean you can hook up a trailer with 1,200 lbs hitch weight, throw on a good WDH that brings it down to 1,000 lbs "hitch" weight and yer good to go.
An even easier way to get your hitch weight is to buy one of these:
Sherline Trailer Tongue Weight Scales
Easy peasy.
Tom