Truck Camper COG

If you don't have the original documentation, can't find the documentation anywhere online, and it's not marked on the camper itself, then you're out of luck.

You've only got a few inches of range in which to install the StableLift, and a few inches one way or the other isn't going to be a deal breaker. After all, there are people moving around the camper all the time, and the water shifts from front to rear as it is used.

I hesitate to post this but I think it is worth discussion.

I have two trucks. They are as follows:

1 One is a '96 Dodge 2500 Ext Cab DSL long bed

2 The second is a '04 Dodge 3500 Quad Cab DSL 4x4 DRW long bed

I have used each truck to carry the same 4000 lb TC and I have weighed each truck with and without the TC several times. The TC sits in the same position in the bed of either truck. I have placed the TC on a pipe and balanced it to locate the center of gravity, which is 4" in front of my rear axle.

I do understand the rear springs will have an impact on this, but I was always of the thought the following to be true:

1 When you loaded the TC, if the front of the truck dropped more than the rear, the COG was in front of the rear axle.

2 When you loaded the TC, if the rear of the truck dropped more than the front, the COG was behind the rear axle.

3 When you loaded the TC, if the front and rear of the truck dropped the same amount, the COG was over the rear axle.

This is true on my '96 Dodge Ext Cab, it drops in the front and about wtp lbs of weight is added to the front axle.

It is not true on my '04 Dodge Quad Cab DRW 4x4. The front axle is lighter by about 60 lbs.It appears the wheelbase has a major effect.

Wayne

Center of Gravity is adjustable on every unit, adjustable by how you load your 'stuff'. By that, I mean the heavier items not clothes or books...

Heavier stuff forward moves the Cg forward and full tanks move it rearward. My FW, batteries and utilities are all forward and I carry my tools and items like chainsaw and winch on the floor of the truck in the backseat which moves the 'adjustable Cg forward as well.

I'm nowhere near or at my maximum axle loading so while it makes no difference for me, it 'may' help with handling. Never noticed any issues however. My truck always rides like a lumberwagon. Just part of it's 'charm' I guess.

The reason I am asking is because I want to purchase a Stable Lift for the camper and when I install it, I would like the Stable Lift to be in the proper position. My truck tells me the COG in glove box but was curious if campers list there COG somewhere as I don't have any original documents. Thanks for all the help

I think if my TC CG is over the center of the axle, I can put at least 500 lbs over the rear bumper just based on the OEM numbers. As built, my truck has 500 lbs tongue weight stamped on the rear bumper. I bet it is limited more by the strength of the bumper than the truck.

My TC (11.5 ft) weight is 3800 lbs. My black tank and gray tanks are on the small side, but both are behind the rear bumper. I don't care if they are empty or full, my truck handles the same.

Wayne

COG will be always important with longer campers.
On my 11-9 camper COG is behind rear axle with empty holding tanks. The 6300 lb add 6500 lb on rear axle, leaving not mach load reserve.
Meaning don't even think of driving with gray water farther than to the end of campground.
I mount Honda 3000 on front platform and it changes a lot, but doesn't look too good.

I find the center of gravity topic to be peculiar simply because manufacturers go out of their way to design the camper to have the ideal center of gravity but then all of the holding tanks are typically in the back of the camper. As an example, my fresh water tank sits at the very front of the camper and with 40 gallons weighs 333 lbs. However my holding tanks are pretty much over the tailgate meaning my center of gravity is going to vary widely just based off where my fluids are. I suspect most other campers are similar.

Back to your question at hand, is finding the COG of particular importance or are you just curious to know for knowledge's sake?

Rustofer is mostly correct.

That calculation assumes the truck stays level. If it doesn't, and the truck tilts backwards due to load (or forwards, quite unlikely), it will shift the weight and the COG more towards the rear axle.

Then you may have to do some trigonometry, but it will be largely irrelevant.

:)

Either way, the weight will tell you where the COG is.

Are you trying to avoid a problem or just curious? A 10 ft TC would be made for a 8ft bed. That's really all that you should need to know.

If it is about weight on rear axle, you'll have to go to a scale to know for sure.

Here's one idea to find your true camper COG from a weigh scale:

Weigh your truck, front and rear axle weights separately, without the camper.

Re-weigh with your camper, with the same truck conditions (passengers, fuel, etc) and get the loaded front and rear axle weights.

Your total weight difference is your camper weight (obviously).

Knowing your wheelbase and the difference in axle weights, you can calculate your exact COG.

The proportion of camper weight carried by your front axle will be equal to the proportion of distance between your rear axle and your camper COG. If your loaded front axle becomes lighter, your COG is behind your rear axle.

Here's an example:
Unloaded front axle 4500 lbs.
Unloaded rear axle 3000 lbs.
Loaded front axle 4700.
Loaded rear axle 6500.
Wheelbase 160"

Camper weight: 3700 lbs.
Proportion of camper weight on front axle = 200/3700 = 0.054 or 5.4%
5.4% of 160" = 8.6"
So your true COG lies 8.6" ahead of your rear axle.

Of course, that is true only for the way your camper is loaded. Changing the weight distribution in the camper (water, food, etc.) may change your actual COG.

Hopefully this makes sense. I've dashed it off pretty quickly, so if I've made an error, I hope someone will point it out.