Help with hitch / tongue weight
Hello All! I'm in the early stages of camper shopping (wanting to upgrade) and I would love some help understanding the tongue weight limits. I have read on 1000 different sites that the max tongue w...
Forum Discussion
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.
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.
