Forum Discussion

jayspi's avatar
jayspi
Explorer
Mar 17, 2019

Need help figuring out why my rig is overweight

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?
  • jmtandem's avatar
    jmtandem
    Explorer II
    Mar 17, 2019
    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.
  • jayspi's avatar
    jayspi
    Explorer
    Mar 17, 2019
    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's avatar
    BFL13
    Explorer II
    Mar 17, 2019
    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-fleetwood-gearbox-toy-hauler-floorplan-395fs3g-tr3484
  • maddog348's avatar
    maddog348
    Explorer
    Mar 17, 2019
    Good Luck ~~ Those kind of #s kept me up many a night. Still would if I would take the time to worry over it.

    JM2¢ ~~ 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's avatar
    pauldub
    Explorer
    Mar 17, 2019
    Sounds like the manufacturer's dry weight is simply grossly incorrect. You have to believe the scales.
  • rk911's avatar
    rk911
    Explorer
    Mar 17, 2019
    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.
  • jayspi's avatar
    jayspi
    Explorer
    Mar 17, 2019
    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's avatar
    jayspi
    Explorer
    Mar 17, 2019
    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.
  • JIMNLIN's avatar
    JIMNLIN
    Explorer III
    Mar 17, 2019
    I would get a reweigh if I didn't think numbers were right. I wouldn't stress over being above the trailers GVWR but being over axles (tires/wheels and spring pack) isn't a good idea.
    If the reweigh repeats I would buzz Grand Design with your numbers and see if they may want to upgrade to 8k axles.

    It would help if the trailer had been weighed before loading it with personnel "stuff". I always weighed my GN trailers (flatbed and stock) before putting them in service. That way I had a good idea how much freight/livestock could be loaded and still be under the trailers GAWRs.

About Technical Issues

Having RV issues? Connect with others who have been in your shoes.24,188 PostsLatest Activity: Jan 18, 2025