ChooChooMan74 wrote:
Travel trailers need 3 passes. Truck alone, truck and trailer with WDH on, and truck and trailer with WDH off (but sitting in the bed of the truck).
Reason you need 3 is because with the WDH engaged, you can see what your true tongue weight is, and can't determine how much is transferred off the rear axles and to the front and trailer axles.
If you don't have weights for "truck and trailer with WDH off", you can get a reliable estimate of TW by applying some physics and algebra to the results of the other two passes.
Even if you do have the loads from "truck and trailer with WDH off", you don't necessarily get an accurate measure of tongue weight.
If the hitch is depressed too much by the TW, the TT is in a "nose down" attitude and that can give an indicated TW which is different from the actual TW.
Ron