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 > Need help figuring out why my rig is overweight

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jayspi

USA

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Posted: 03/16/19 07:26pm Link  |  Quote  |  Print  |  Notify Moderator

Hey folks, this might be a weird question, but I need help figuring out why my rig is overweight. Let me explain.

We have a Grand Design Momentum 354M 5th wheel toy hauler. Here are the stats that matter:

  • Dry weight: 13,400
  • Pin weight: 2,700
  • GVWR: 16,500
  • Axle Rating: 2 x 7000
  • Fresh water capacity: 157 gallons
  • Fuel capacity: 60 gallons


Basic arithmetic tells us that with full fresh water and fuel tanks but nothing else, the weight is 15,211 pounds. That leaves us with 1,289 pounds for cargo.

The problem is, when we are fully loaded with cargo and full fuel and fresh water tanks, the CAT scales put me at a whopping 17,500 pounds (3,220 on the pin and 14,280 on the axles).

I know that CAT scales are reliable, but I still used 2 different ones to be sure. I also weighed the truck without the trailer attached so I could get an exact calculation.

Here's the thing, though: There's absolutely no way we have that much cargo. We use the garage for our son's bedroom. We don't have "toys." The heaviest things we have in the RV are our washer/dryer combo (150~ pounds), a cabinet we added in the garage (<200 pounds) and our mattress (100~ pounds).

Other than that, all we have are food, clothes, baby toys, and miscellaneous items like some camping gear and alpine skis. None of it weighs more than 30 pounds, and there isn't a lot of it. We aren't hardcore minimalists, but we don't like having a lot of stuff. We do regular purges of unneeded items.

I can see MAYBE having 500-800 pounds of cargo (after the items listed above), but there's no way that we have a total of 2,289 pounds (which is what we'd need to hit 17,500 pounds).

There's also no way that we have 14,280 pounds on the axles. The only things in the garage are the cabinet, washer/dryer, our son's crib, and some baby toys.

The only thing that I can figure is that I'm somehow using the scales wrong. However, I'm using the 3 boxes and getting weights for steer axle, drive axle, and trailer axle, so I don't think I've positioned it wrong.

Does anyone have any ideas?


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jmtandem

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Posted: 03/16/19 07:31pm Link  |  Quote  |  Print  |  Notify Moderator

RV manufacturers are notorious for listing dry weights without any options. Unless they weighed the coach you have no idea what it really weighs until you take it to a scale as you did. The coach more than likely weighs way more than listed as a dry weight. Figure water at 8.3 pounds per gallon, batteries, propane, etc. It all adds up. From the scale weights you are actually over your axle rating and maybe tire ratings as well.


'05 Dodge Cummins 4x4 dually 3500 white quadcab auto long bed.

jayspi

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Posted: 03/16/19 07:36pm Link  |  Quote  |  Print  |  Notify Moderator

jmtandem wrote:

RV manufacturers are notorious for listing dry weights without any options. Unless they weighed the coach you have no idea what it really weighs unless you take it to a scale as you did. The coach more than likely weighs way more than listed as a dry weight. Figure water at 8.3 pounds per gallon, batteries, propane, etc. It all adds up. From the scale weights you are actually over your axle rating and maybe tire ratings as well.


Yes I understand what the scales are telling me, I just don't think it's right. I think I'm doing something wrong.

I agree that RV manufacturers don't give an exact weight, but I don't see them being roughly 1,000 pounds off.

Edit: Keep in mind that this is a toy hauler. It's meant to carry quads or dirt bikes, etc, in the garage. If the numbers the scales show are right then the only way you'd be able to use this as a toy hauler would be to not fill your tanks. That kind of defeats the purpose.

BFL13

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Posted: 03/16/19 07:55pm Link  |  Quote  |  Print  |  Notify Moderator

You are assuming that the spec dry weights are correct. Usually that does not include "options" you might have that weigh something, that you thought were included in that dry weight.

Options might include fibreglass sides instead of aluminum (add 500 lbs) double pane instead of single pane windows, winter grade insulation package, air conditioner, whatever.

Note your spec dry pin weight percentage is 20% (2700/13400) but your measured 3220/17500 is 18%. At GVWR 16500 and 20%, pin would be 3300. No effect on overall weights, but you might be loaded to the rear of the axles, or else nose high when hitched. You can adjust the hitch and king pin heights to get level if need be.

This says the 13,400 UVW "is based on average weight" whatever that really means

https://www.granddesignrv.com/showroom/2019/toy-hauler/momentum/floorplans/354m

At 16500 GVWR with pin at 3300, that leaves axle wt at 13,200 which gives you 800 margin under the 2-7000. So compared with UVW axle of 13400-2700 = 10,700 that gives you 13200-10700 = 2500 you can add to axle wt. IMO your 39 ft rig should have three axles. I have seen toy haulers that long with three. Oh well.

https://www.rvusa.com/rv-guide/2008-flee........rbox-toy-hauler-floorplan-395fs3g-tr3484

* This post was last edited 03/16/19 08:18pm by BFL13 *   View edit history


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maddog348

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Posted: 03/16/19 07:56pm Link  |  Quote  |  Print  |  Notify Moderator

Good Luck ~~ Those kind of #s kept me up many a night. Still would if I would take the time to worry over it.

JM2ยข ~~ YMMV

Note!! weighed every pot/pan ~ pair of shoes/pants ~ can of peas/beans ~ shirt/coat etc/etc/etc every single piece down to 1/4 oz. Don't travel much but sleep a lot better. K





pauldub

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Posted: 03/16/19 08:08pm Link  |  Quote  |  Print  |  Notify Moderator

Sounds like the manufacturer's dry weight is simply grossly incorrect. You have to believe the scales.

time2roll

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Posted: 03/16/19 08:10pm Link  |  Quote  |  Print  |  Notify Moderator

Trust the scale. What are the tires rated?
Only option I see is to move stuff forward assuming the truck payload is not maxed out already.

https://www.granddesignrv.com/showroom/2019/toy-hauler/momentum/floorplans/354m

* This post was edited 03/16/19 08:21pm by time2roll *


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rk911

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Posted: 03/16/19 08:22pm Link  |  Quote  |  Print  |  Notify Moderator

1). unload everything from the 5'er...everything. no cargo of any sort.
2). empty the tanks of water, fuel, lp. water = 8lbs/gal, gas = 6lbs/gal, lp = 4lbs/gal
3). weigh the 5'er and compare to the mfg dry weights.

the only thing that makes sense is the factory weights you have are wrong.


Rich
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jayspi

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Posted: 03/16/19 08:29pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

You are assuming that the spec dry weights are correct. Usually that does not include "options" you might have that weigh something, that you thought were included in that dry weight.

Options might include fibreglass sides instead of aluminum (add 500 lbs) double pane instead of single pane windows, winter grade insulation package, air conditioner, whatever.

Note your spec dry pin weight percentage is 20% (2700/13400) but your measured 3220/17500 is 18%. At GVWR 16500 and 20%, pin would be 3300. No effect on overall weights, but you might be loaded to the rear of the axles, or else nose high when hitched. You can adjust the hitch and king pin heights to get level if need be.

This says the 13,400 UVW "is based on average weight" whatever that really means

https://www.granddesignrv.com/showroom/2019/toy-hauler/momentum/floorplans/354m


Good call on the pin weights. I'm going to lower it a pin.

I'm pretty sure Grand Design weighs them when they come off the assembly line. I'll call them Monday to be sure. I say that because on the sticker by the propane tanks they list the precise weight. I didn't write it down, but it was an exact number to the pound, and it was slightly less than 13,400.

If they did weigh it, then I'm guessing it was weighed with the options that the dealer ordered it with. I'll call them Monday to be sure. Either way, I went through the list of optional equipment on our RV and the only thing that weighed more than a few pounds was the generator. I'm sure that's a few hundred pounds, but still not enough to explain the discrepancy that I'm seeing.

I'll give Grand Design a call on Monday to try to find out if they weighed it, and, if so, if it included the dealer options. I'm also going to empty the tanks and take it across the scales and see what I get.

Thanks for the advice, folks. It sounds like I'm going across the scales correctly...I just need to figure out why I'm 900 pounds heavier than I should be. Hopefully Grand Design can help me figure out the base weight of the rig and then I can go from there.

P.S. - I'm not over the tire rating, and I can get below the axle rating by dumping a little water. However, I am very concerned about the total weight.

jayspi

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Posted: 03/16/19 08:32pm Link  |  Quote  |  Print  |  Notify Moderator

rk911 wrote:

1). unload everything from the 5'er...everything. no cargo of any sort.
2). empty the tanks of water, fuel, lp. water = 8lbs/gal, gas = 6lbs/gal, lp = 4lbs/gal
3). weigh the 5'er and compare to the mfg dry weights.

the only thing that makes sense is the factory weights you have are wrong.


I'm pretty sure Grand Design weighed it. The 13,400 number is from their web site, but the sticker by the propane door gives a precise number that is slightly less than 13,400.

I'm going to call them Monday and find out. If they did, then I can empty the fresh water and take it over the scales. That will tell me how much cargo we have.

Also, thanks for pointing out that gas is 6 pounds per gallon. Good catch.

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