Campin LI wrote:
If I were to apply a tongue weight to the back of my truck, the back of the truck will go down and the front will go up. Before applying weight distribution, if I raise the back of my truck by 2 inches with airbags, theory says I would raise the front of my truck by 2 inches as well because the truck is still loaded the same way. This may not actually happen because of the spring design but the front should still rise somewhat. Now if I apply my WDH, using the directions, I would return the front of the truck to 50% of it's unhitched height.
Let's try putting some numbers to this. Let's assume a 1000# TW causes 500# to be removed from the front axle and 1500# to be added to the rear axle when the TW is applied with no WD. Let's also assume the front suspension coefficient is 500 lb/inch and the rear is 750 lb/inch.
The TW with no WD could cause the front to rise 500/500 = 1" and the rear to drop 1500/750 = 2". You now add pressure to the air bags causing the rear to rise 2". The added load on the rear axle does not change. It still is 1500#. As the rear rises, the rear springs decompress and they transfer 1500# of their load to the air bags.
Since the amount of load added to the rear remains at 1500#, the load removed from the front remains at 500#. The front remains at its previous height of 1" above the unhitched height.
If you then apply enough force to the WD bars to cause 500# to be added back onto the front axle, you will have 100% FALR and the front axle will drop 1" back to the unhitched height.
I don't know of any theory which says the front of the truck should rise when you add pressure to the bags without WD being applied. But, it would be easy to test experimentally. Just measure the following:
1) Front and rear heights for truck only with no pressure in the bags and trailer not hitched.
2) Front and rear heights for truck with trailer hitched and no pressure in bags.
3) Front and rear heights for truck with trailer hitched and pressure in bags.
Wouldn't you agree that I need to be careful with which unhitched height I use? If I use the unhitched height before air was put in the airbags, I will end up with more weight transferred to the front axle than is recommended. By using the height after air is in the airbags, there will be no noticeable change in the stance unless I use the WDH to transfer more weight to the front.
Yes, I would agree you need to be careful. IMO,You need to use the height from 1) above. No matter what you do in between -- if, in the end, the front end height is returned to the unhitched height, the front end load will be close to the unhitched load.
Before we move on to the rest of your post, I suggest we try to resolve our different points of view on this fundamental issue.
Ron
P.S. I'm glad to see you're still posting here. At my age, I need lots of thought-provoking questions and comments to stimulate my declining thought capacity.
