gemsworld wrote:
The 720 lbs added to the rear axle also includes about 90 lbs of gear in the back of the SUV and another 55 lbs for the Equalizer WDH. I'm guessing the actual tongue weight is about 575 lbs, which seems to be about right for a TT with a 4,882 lb GVWR.
You cannot use only the rear axle load change to determine tongue weight -- you also must include the front axle load change.
You also cannot use the TV's axle loads when hitched with WD applied to determine the tongue weight -- you must use the axle loads with TT attached and no WD applied.
And, if you have the Equal-i-zer brand hitch, the weight probably is closer to 100# than 55#.
If you add 90+55 = 145# to the first weighing to correct for cargo and WDH weight which was not included, the TV's first GVW would have been 4880+145 = 5025#.
If you add 100# to the second weighing to correct for 2/3 tank of gasoline which was not included, the second GVW would have been 5780#.
The TV's weight, with TT attached and WD applied, would have increased by 5780-5025 = 755#.
However, that does not mean the TT's tongue weight is 755#.
In order to increase the front axle load by 80# while increasing the TV's GVW by 755#, a load of approximately 270# would need to be transferred to the TT's axles.
This means the indicated tongue weight was approximately 755+270 = 1025#.
If you want a better estimate of tongue weight, you need to re-weigh your rig.
The weight of TV occupants and cargo should be the same for all weighings.
The WDH should be in the receiver and the WD bars should be in the rear of the TV for the "TV only" measurements.
A second set of weights should be taken with the TT attached and the WD bars in place, but with no load applied to the WD bars.
The sum of the TV's axle loads from the second weighing minus the sum from the first weighing will be equal to the TT's tongue weight for that loading condition.
Ron
