CG and Weight Question

[Mike3]

My truck has a GVWR of 16K with 11K rear axle and 6K front axle. Solo the front weighs 4900#. After loading the TC the front weighs 320 lbs less. So loaded I have 9820 lbs on the rear.

The CG mark from ALP is about 1.5" behind the center of my rear axle. When loading the TC the first time I place a 2X4 up against the front bed for the TC bumpers to nudge.

Question: If I remove the 2x4 and move the camper 1.5" forward so the CG is closer to the center of the rear axle what difference if any would that make?

I did not do that to begin with because it's a tight fit under with the sewage pipe and my rear truck lights but I can do it very carefully if it makes significant difference. Thanks

[jimh406]

The bumpers on the front of my camper are about 1.5 as well. I really don't think it's going to matter that much.

[wnjj]

Artum Snowbird wrote:
It goes like this. Assuming your wheelbase between your axles is 12 feet. (I know it's not, but this makes it easy to understand.)

You have lost 320 pounds 12 feet ahead of the rear axle. You have likely gained 640 pounds 6 feet behind the rear axle. You see how the weight times the distance is the same in each case.

CG marked on campers are for a dry measurement only, but once you fill it with your stuff, in your case for sure, you have more weight behind the real axle than in front of it.

So again, assuming 144 inches to the front axle. Moving the camper forward 1.44 inches will only take off about 1/100 of the weight on the front. Only 3.2 pounds.

What you have to do is shift significant heavy things from the back of the camper to the truck if you can.

Your math is a bit off. Moving forward will put more weight onto the front axle and the amount will depend upon how far behind the axle the COG is at the start. We do not have enough information to determine that but I'll take a guess:

Let's assume the camper is 4800 lbs. 4800 / 320 is 15. This means 1/15th of the camper's weight is removed from the front axle. This in turn means the COG is 1/15th of the wheelbase distance behind the rear axle. Using your 144" assumption that works out close to 9.6" behind. So in that case moving 1.5" forward would restore about 50 lbs (320 * 1.5/9.6) of the 320 lbs originally lost.

For what it's worth, losing a little front axle weight is not a big deal. Camper loading guides provided with the truck will likely show an acceptable COG range in front and behind the rear axle. Past GM publications I've looked at only were concerned with the front and rear axle loading ratio as a percentage of each other.

[campn4walleye]

Mike,
I don't know if it will help you, but we had to move our slinky keeper. DH just unbolted it and moved it to the other side, which ended up making it more convenient and gave more room (the width of the tube) to move the TC forward.

Your TC is much larger but it made a difference for us.

[Artum_Snowbird]

It goes like this. Assuming your wheelbase between your axles is 12 feet. (I know it's not, but this makes it easy to understand.)

You have lost 320 pounds 12 feet ahead of the rear axle. You have likely gained 640 pounds 6 feet behind the rear axle. You see how the weight times the distance is the same in each case.

CG marked on campers are for a dry measurement only, but once you fill it with your stuff, in your case for sure, you have more weight behind the real axle than in front of it.

So again, assuming 144 inches to the front axle. Moving the camper forward 1.44 inches will only take off about 1/100 of the weight on the front. Only 3.2 pounds.

What you have to do is shift significant heavy things from the back of the camper to the truck if you can.