5th Wheel Basement Storage Weight

[Jseitz]

Is there any rule of thumb about how much of the weight of stuff in the front basement storage area of the average 5th wheel goes to the pin weight based on a percentage? I know it would not be 100% but would guess it would be over 50%. Thank you and I appreciate all of the shared knowledge on this forum. I have learned a lot!

[Canonman]

I'll guess it's closer to 100% than 50%. If the wheels/axels are the fulcrum point and the storage is close to the front, then most of the weight has be carried by the pin.
That's my guess. I'm sure there is a formula somewhere to figure it exactly.

[chuckster57]

I’d like to know if there’s a formula. I do have a scale, next time I install a gen in the front compartment I’ll weigh before/after if I remember.

[wiredgeorge]

A quick check indicated your trailer has an 1885 lb. payload. You thinking about how you can get 1885 lbs in the front pass through? I would start by subtracting what is in all the various tanks and anything else you have stashed in the cabin but still can't imagine why some would want to put half a ton in the pass through. In any case, I doubt Einstein could figure out a formula for how much you pin weight would be but since you have a starting pin weight of 810 lbs (per Keystone I guess) and even doubling that, you likely won't sag the springs on your Superduty. You could also ride out to Modesto and let Chuckster weight it for peace of mind!

[Jseitz]

I am asking for a friend who has a 5er. I am a single guy with a dog. My TT Cougar can carry a years supply of milk bones...LOL

[Frank G]

Measure the distance from the center of the wheels to the pin. Draw this out on a piece of paper. Next measure from the pin to the center of the load you are adding, go back to your paper and put a mark in the appropriate spot.
If the load is in the center then the load is shared equally. If it is off center then the load shifts proportionately. Easy

[Snoking]

Originally Posted by Frank G

Measure the distance from the center of the wheels to the pin. Draw this out on a piece of paper. Next measure from the pin to the center of the load you are adding, go back to your paper and put a mark in the appropriate spot.
If the load is in the center then the load is shared equally. If it is off center then the load shifts proportionately. Easy

Isn't the over hang behind the axles in play also, negating some of the load in the front storage area? Chris

[chuckster57]

Originally Posted by wiredgeorge

You could also ride out to Modesto and let Chuckster weight it for peace of mind!

I have a 0-2000 and a 0-5000 in my tool box at work. I suppose I could bring it home for a day or two. It is interesting to see how much different the actual weight is vs advertised weight.

[rhagfo]

Originally Posted by Frank G

Measure the distance from the center of the wheels to the pin. Draw this out on a piece of paper. Next measure from the pin to the center of the load you are adding, go back to your paper and put a mark in the appropriate spot.
If the load is in the center then the load is shared equally. If it is off center then the load shifts proportionately. Easy

This doesn't work as the tandem axles are true pivot point.
If your friend is worried about how much of the weight in the basement goes to the pin, he is likely worried about weight of the TV. If he is that worried about pin weight he likely needs a smaller 5er or larger TV.
Even when we had our 2001 Ram 2500 that was 1,700# over GVWR, I didn't try to figure it out. I was only worried about rear axle rating and tire rating, and I had plenty of room to spare.
Now with the 2016 Ram 3500 DRW, I have at least 1,300# of spare payload.

[notanlines]

Actually both Frank and Rhagfo are onto the correct answer. With the tandem axles being the pivot point there will be no absolute answer, but barring an actual weight at the CAT scales, it will put your friend close enough to keep him in the ballpark. And no, the weight to the rear of the tandems will have no bearing on offsetting any ADDITIONAL weight stored in the basement.

[Canonman]

Let me see if I understand this correctly
Jimmy and Bobby are playing on the teeter-totter. Both boys are about the same size but Jimmy's a year older and 15% heavier. So, the teeter-totter can't exactly balance. Billy sees the two boys playing and wants to join in so he hops on the teeter-totter with Jimmy and of course the teeter-totter drops to the ground on Jimmy's end. So, how much of Billy's weight was carried by the fulcrum (center) of the teeter-totter and how much was carried to Jimmy's end of the teeter-totter??
Don't you just love story problems

[Snoking]

Originally Posted by Canonman

Let me see if I understand this correctly
Jimmy and Bobby are playing on the teeter-totter. Both boys are about the same size but Jimmy's a year older and 15% heavier. So, the teeter-totter can't exactly balance. Billy sees the two boys playing and wants to join in so he hops on the teeter-totter with Jimmy and of course the teeter-totter drops to the ground on Jimmy's end. So, how much of Billy's weight was carried by the fulcrum (center) of the teeter-totter and how much was carried to Jimmy's end of the teeter-totter??
Don't you just love story problems

But Bobby stores a lot of his toys, including his marble collection that is quite heavy, in the cabinets at his end of the teeter-totter

[Stircrazy]

to get a rough idea you can use simple math. measure the distance from your wheels to your pin. lets say that is 20 feet for argument. so lets say that your storage is 8 feet back from your pin, so 12 feet from the wheels so at that distance approximately 60% of the weight will be on the pin and 40% on the tires. if you were only 4 feet back from the pin then 20% would be on the tires and 80% on the pin.

steve

[Jseitz]

Thank you for all of the feedback. I shared the advice on the measurements and convinced my buddy to go get weighed at the local Cat scale. I have already looked at his door stickers and know he is over capacity. I think he is doing his best to get back into a close to legal capacity status until a bigger truck can be purchased. My buddy is a victim of the RV salesman telling him "sure you have enough truck" .

[rcwaz]

I asked this question years ago. The response was that under static conditions any load between two points is equally is born by both points of bearing. However our 5th wheels are under dynamic load when moving, stopping, etc. There in lies the problem. It’s also an issue probably taken into consideration by the engineers who specified the pin weight and the hitch capacity and the truck GCWR and GAWR.

[LewisB]

Originally Posted by Stircrazy

to get a rough idea you can use simple math. measure the distance from your wheels to your pin. lets say that is 20 feet for argument. so lets say that your storage is 8 feet back from your pin, so 12 feet from the wheels so at that distance approximately 60% of the weight will be on the pin and 40% on the tires. if you were only 4 feet back from the pin then 20% would be on the tires and 80% on the pin.

steve

Originally Posted by rcwaz

I asked this question years ago. The response was that under static conditions any load between two points is equally is born by both points of bearing. However our 5th wheels are under dynamic load when moving, stopping, etc. There in lies the problem. It’s also an issue probably taken into consideration by the engineers who specified the pin weight and the hitch capacity and the truck GCWR and GAWR.

Steve and several others have correctly pointed out that additional applied load between the pin and axles is proportional to the distance from each end of the supports (pin and center of axles). And load applied aft of the axles does not play a role when considering ADDITIONAL weight applied ahead of the axles. The concept that load is equally applied to both ends is not correct. Think of a tractor-pull in which the weight applied to the drag bars on the front of the weighted trailer (the end with no wheels) is progressively increased by a heavy weight being moved from the rear of the trailer with wheels to the front of the trailer with the drag bars.

It is true, however, that there are dynamic forces that change the loaded weights on both the pin and axles as the rig is in motion. But those forces are more a function of speed, starting, stopping, shifting liquid (e.g. in tanks), road conditions, driving style, etc; dynamic forces are typically accounted for in vehicle design and are beyond the scope of the OP.

[Stircrazy]

Originally Posted by LewisB

Steve and several others have correctly pointed out that additional applied load between the pin and axles is proportional to the distance from each end of the supports (pin and center of axles). And load applied aft of the axles does not play a role when considering ADDITIONAL weight applied ahead of the axles. The concept that load is equally applied to both ends is not correct. Think of a tractor-pull in which the weight applied to the drag bars on the front of the weighted trailer (the end with no wheels) is progressively increased by a heavy weight being moved from the rear of the trailer with wheels to the front of the trailer with the drag bars.

It is true, however, that there are dynamic forces that change the loaded weights on both the pin and axles as the rig is in motion. But those forces are more a function of speed, starting, stopping, shifting liquid (e.g. in tanks), road conditions, driving style, etc; dynamic forces are typically accounted for in vehicle design and are beyond the scope of the OP.

the only thing I would add is that adding weight behind the axels does factor in, it will lighten the nose weight by an amount. I have seen people use eight on the rear of the RV to get there hitch weight dialed in to there payload capacity. so it can also be useful but the same concepts apply but in reverse.

Steve

[LewisB]

Originally Posted by Stircrazy

the only thing I would add is that adding weight behind the axels does factor in, it will lighten the nose weight by an amount. I have seen people use eight on the rear of the RV to get there hitch weight dialed in to there payload capacity. so it can also be useful but the same concepts apply but in reverse.

Steve

Absolutely correct; however, the OP was a question regarding distribution of added weight to the front storage area between the axles and the pin.

I have an unusual situation in which I have more TV capacity with a DRW than I have toy-hauler trailer axle capacity. We load a relatively heavy SxS in the back, so I am constantly trying to shift weight as far forward as possible. Shifting weight forward of the axles and as close to the pin as possible certainly helps; better yet, I have moved several heavy items (big toolbox, Grill, etc.) into the back seat of our crew cab dually. We recently traded an older three axle toy hauler for a newer two axle toy hauler. So I have had to re-think how the trailer is loaded. Our recent trip to the scales has shown us very close to where we need to be.

[wiredgeorge]

The OP was asking for a friend. The reason for the query was unclear. The last the OP posted in this thread was a week ago. Lord, all this physics stuff tells me that some of you boys didn't play football. I think my head exploded!

[LewisB]

Originally Posted by wiredgeorge

The OP was asking for a friend. The reason for the query was unclear. The last the OP posted in this thread was a week ago. Lord, all this physics stuff tells me that some of you boys didn't play football. I think my head exploded!

Actually, I played tackle on my high school football team that won the Colorado state class A championship in 1966. I haven’t thought about that in years!

Did not mean to make your head hurt. You must have access to information not available to the rest of us. I could see the 0P logged on yesterday but don’t know when he last posted. Nor can I speak to his motivation for this post. Nevertheless, since this thread is searchable in the future I thought it would be good to get full information posted. Hope that makes sense.