Good morning Onyrlef:
On trailers that do not have weight distributing suspensions, it is easy to have one trailer axle carrying more weight than the other axle. This results in the tires on one axle having better friction between the tires and the road. The lighter axle will have less friction. Therefore, the wheels on the lighter axle may lock up in a panic stop sooner than the wheels on the heavy axle. And with the trailer brake gain set, the heavy axle can't use the extra traction. What this means is, you won't have optimum braking authority from the trailer wheels in a panic stop situation.
This is why you want the trailer really close to level, to evenly distribute the weight on all trailer axles, whether there are two or three axles. It is very common for TTs not to have weight distributing suspensions.
In order to get the weight values on each trailer axle, we need to isolate each axle on a scale pad by itself and take another weigh. If you have only two trailer axles, you can "split" them by putting the front axle on scale pad #2 leaving the rear axle on scale pad #3 by itself. This way, you can get an accurate weight for both axles in one re-weigh.
If both axles weigh the same, or very close there to, you will have better braking authority from all trailer wheels. An added benefit will be more even tread wear.
My reference to weighing three times is just this. I always weigh the combination first since that's how we pull into the truck stop. For the second weigh, you would pull just far enough forwards to put trailer axle 2 just barely, but fully, on scale pad #2. This will leave the rear trailer axle on scale pad #3 by itself. Then when you take a second weigh, you will have accurate weight figures for each of two trailer axles. This assumes your tow vehicle rear axle that was on pad #2 has move forward enough to where it is off of pad #2 and only the front trailer axle is on pad #2 now.
The third weigh is the tow vehicle only, without the trailer. This should be weighed with the exact load as it was loaded when you pulled onto the scale to weigh the combination, including driver and all passengers. Weighing the tow vehicle exactly as it was loaded when the combination vehicle was weighed is very, very important. If it is not the same, some of the weights that must be calculated, such as hitch, or tongue weight, will not be valid.
I always fill up on diesel, exhaust fluid, fresh water, and generator gas. I have a 5th wheel toy hauler with a full tank of gas for the toys as well. Since I have three trailer axles, I have one more step to way two trailer axles separately. So that gives me four weighs. I take all four weighs within about 45 minutes or less. Then go inside to get all four of my scale slips.
After weighing my trailer axles, I pull off the scale to park. I drop my trailer in the parking space while I drive my tow vehicle only back onto the scale to weigh it.
I hope I've answered your question. If not, please let me know and I'll try again. This is something we all need to fully understand so we can know that our vehicles are safe to drive. lol.
Dave