Help with hitch / tongue weight

IDoMyOwnStunts wrote:
The TV rear axle is the fulcrum (pivot point). The entire truck is the lever. The WD system is the upward force applied to that lever behind the rear axle. The weight of cargo behind the rear axle AND the weight of the tongue of the trailer both apply downward forces behind the rear axle. Thus the WD system must apply enough upward force to counter both the weight of the trailer tongue AND the weight of the cargo behind the axle in order to restore weight to the front wheels.

The place where it gets complicated is that you actually have two levers, the other one with the fulcrum at the travel trailer wheels. However, the purpose of the WD system is the same. It is an upward force against that lever and that force still must act against the total downward force applied by both the trailer weight forward of the axles (the tongue) and the cargo behind the rear axle of the TV.

Ok, so why does the receiver rating need to take into consideration the weight of any cargo behind the rear axles? Because it needs to be sized to cope with the counter force applied by the WD system back through the receiver. Even though the WD system may take some weight off the ball, the full force of that WD system is still transmitting through the receiver back to the truck (minus the weight transferred back to the travel trailer tires).

Think about this. If you did not have any trailer hooked up and you loaded cargo behind the rear axle, that will take weight off the front axle. This is simple lever physics. The truck is a seesaw that wants to pivot on that rear wheel. Too much force on the back side of the truck will lift the front wheels off the ground. And weight is a force. Only, in this case, you have no means to restore weight to the front axle other than moving the cargo.

So, the bottom line is that if you want to restore all of the weight taken off the front wheels when you hook up your trailer, you must size and adjust your WD system to account for cargo behind the rear wheels. If you do not, you simply will not restore all of the weight back to the front wheels or you may overload your current system trying to restore that weight. Does it matter? That is entirely up to you. As for me, I felt the need to upgrade my receiver.

Thanks for reading.

Edit to add: Yes, I realize that the springs from the truck and trailer suspension provide upward force as well. That still doesn't change the pivot points nor the forces on the receiver/WD system.

THANK YOU, you have summed up what I've been trying to get across and I agree with everything you have said. For some reason I wrongly assumed that providing what I thought were very VALID and AUTHORTATIVE quotes would clarify things, but for some reason did not.

I would just add that in one of my original posts I tried to acknowledge that just how significant this cargo was to increasing what CEQUENT classifies as "HITCH WEIGHT" because it's position relative to the rear axle of the TV and the hitch head can vary and I believe this has an impact on the actual amount of increase in "HITCH WEIGHT" is realized. I can only WAG that this is basically ignored since assuming all the weight is added is the safest position and in 99.9% of the cases will not cause one to really over specify the sizing of the WDH components. In that document from CEQUENT I linked to has a chart for WDH bar ranges vs this "HITCH WEIGHT", but of course that opens the previous "CAN OF WORMS" about some that feel even using bars rated at just what the actual trailer tongue weighs is overkill and not required.

Finally, as I have said I'm probably a little more sensitive to this since my cargo aft of the axle VARIES by hundreds of lbs even during a trip or between trips and that is why I call the cargo "TEMPORARY" and included with pics the 4 fuel cans, generator, tool box, etc that are sometimes carried empty or full with that varying during a road trip between towing days as an example of this "CARGO ADDED" that I was talking about. Conversely, even with my somewhat unique setup I have significant weight (probably close to 1,000 lbs) between the rear of my Van and the rear axle on my Van that is fairly fixed because of the secure storage area that I built along with the sofa-bed and all the tools/parts, etc. that remain there all the time. This weight is "NOT TEMPORARY" and does not need to be accounted for as this "weight" is included in the normal "LOADED" configuration of my Van, is always there, and already accounted for when the WDH was originally setup and adjusted. Of course by the same token one should adjust their WDH with full fuel, and ensure removable items such as spare tires that are normally on the vehicle are all in place since those IMO are really not cargo as CEQUENT is talking about, but a normal loaded condition of the TV. Regardless, the concept and validity of accounting for this "added cargo" weight to the "HITCH WEIGHT" is still valid IMO and should at least be acknowledged and included where applicable. For one to say it has no effect is IMO incorrect. I think this is why CEQUENT specifically says the weight is "CARGO ADDED" where added is the operative word meaning its after the WDH has been set up for what would be considered a normal "loaded" vehicle configuration and even goes as far as trying to include such what I would classify as transient items such as "gas cans, tools, boat motors, etc" in their classification as types of "cargo added" they are talking about. This would also include say extra baggage and even passengers in the very rear seats of say a large SUV that might be there on some trips, but not others. It could also include those 10 cases of beer stored at the rear of say an SUV for that once a year lake campout, beer party for the office, etc. Another example might be taking a golf cart in the bed of a pickup on some trips, but not others unless one would want to go thru the entire WDH setup routine, adjustment, road testing, etc. every time such "added cargo" like a golf cart was or was not there.

Larry