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Undersized axles on Momentum 320G or just poor design?

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  • #16
    Originally posted by GDRV-Megan View Post

    Thanks for the tag and the feedback. I have passed this along to our product manager. I'll update here if I get any feedback. Thanks!

    RoyB beautiful photos!! I'd love to share these on our social media platforms, with your permission! If you'd like us to share, please send them to me at smservice@granddesignrv.com attn: Megan. If you'd like credit or a shout out, please include your first name or Instagram account handle.
    GDRV-Megan Thank you for submitting. I'd be curious as to their answers. I will send you some pictures. I don't have an Insta. Maybe one day when I am bored....

    In further looking into this, I took a gander at the 350G which is an identical trailer, just with an extra 3' on the back half of the trailer, in the garage.

    The rear tires seem to be moved back a whole set.


    320G: Click image for larger version

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    350G: Click image for larger version

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    350G is 550lbs heavier overall than the 320G. 300lbs are on the hitch alone, yet the trailer got longer BEHIND the axles. It looks like moving the axles back approx 24" helped keep the hitch weight in check @ 20%. GVWR is the same as mine though.

    The 351M is 3' longer in FRONT of the axles, and the same size garage as the 320. It has the same axle location, but a better hitch weight allowing better distribution of garage weight since more weight is in front of the axles.

    We were torn between the 351M and the 320G. But, I was concerned about the CCC, which on paper, the 320G won since it was 1200 lbs lighter. I obviously ate that 1200 up quickly with options However, in real world, it appears the 351 was the better choice since the hitch would be unloaded less because the axles are further back on the trailer overall. It looks like they took the frame from a 351M, cut 2 feet out of the middle, and made it into a 320G.
    Model Length Hitch UVW Garage Garage weight Cabin weight Cabin wt/ft
    320G 36'3" 2,300 12,400 11' 1,727 10,674 422lb/ft
    350G 39'10" 2,600 12,950 14'6" 2,276 10,674 422lb/ft
    351M 38'6" 2,785 13,800 11' 1,727 12,073 439lb/ft
    TucsonJim Do you have the tank layouts for the 350G and 351M. I'd be curious to see how they compare. They should be the same on the 351M since the axle placements look the same and the same slide areas. With the axles further back on the 350G I am curious if they just slid the fresh water and fuel cell back into the extra 3' of garage space, or if they moved the fresh water in front of the axles.

    I am also puzzled how the 350G, which is a foot longer than the 351M weighs 850lbs less. Subtracting the garage weight between the 320 and 350 you can figure out that portion of the trailer. The living area of the 351 is 17lbs heavier per foot than the G class models. 467lbs heavier over the 27.5' cabin than the same interior treatments of the G class. I assume the windows, tanks, larger fridge, larger slide attribute to most of that weight. My point being that is helping the balance of 351M more than the 320G despite axle placement on an 11' garage being the same.

    I am very curious what GD comes back with after comparing these couple models.
    Attached Files
    2020 GD 320G
    2021 Ram 3500 H.O. SRW.

    Comment


    • #17
      Originally posted by RoyB View Post
      Do you have the tank layouts for the 350G and 351M. I'd be curious to see how they compare.
      The 350G drawings the moderators have do not show the tanks. (What we have is kind of hit-or-miss when it comes to documentation. GDRV-Megan is working on updating what the moderators have so we can answer these types of questions.)

      I *think* the 351M drawings show the water tank in front of the axles. When looking at the drawings side-by-side, where your combined black/gray tank is over the axles and water tank is under the garage, the 351M is opposite. The gray looks like it is under the garage and the water tank is just forward of the axles. (The latter is a much better placement IMHO.)

      I should also state the 351M has an additional "aux water tank" aft of the gray (under the garage) and there are two fuel tanks all the way aft, so there's potential for quite a bit of weight aft in this trailer if an owner loaded up with fresh water and fuel.

      In summary:
      320G (aft to front): Fuel, Water, Gray(over axles), Black & Gray (side by side)
      351M (aft to front): Fuel tanks (x2), Aux Water, Combined Black/Gray (over axles?), Water, Black and Gray (side by side)

      I think I got that right...Jim, Rob or Brian will correct if I messed something up.

      Howard
      Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

      2017 Ford F-350 DRW, '19 315RLTSPlus

      Comment


      • #18
        Originally posted by howson View Post

        In summary:
        320G (aft to front): Fuel, Water, Gray(over axles), Black & Gray (side by side)
        351M (aft to front): Fuel tanks (x2), Aux Water, Combined Black/Gray (over axles?), Water, Black and Gray (side by side)

        I think I got that right...Jim, Rob or Brian will correct if I messed something up.

        Howard
        Thank you for the information. Very odd that the 2 have the same layout for the most part. 11' garage, half bath off the garage, sinks in the same areas, same slides for the most part. I can't see 2.5' longer mid section making that big an impact on tank placement. The 351 does have larger slides on both sides if that was a concern for tank placement.

        While the 351M has potential for more weight from the tanks, you can also upgrade the axles to 8K lb disk brake units from the factory. Also, with the majority of the fresh water in front of the axles (I am assuming same 115gal on most units) you could easily balance out the extra weight from the aux fresh and 2nd fuel tank behind the axles.

        This appears to be a blatant design error on the 320G.
        2020 GD 320G
        2021 Ram 3500 H.O. SRW.

        Comment


        • #19
          Do you guys think it would be possible to move the fresh water tank to the front of the axles? I am talking to my camper dealer about selling off the 320G and purchasing a 351M, but then it dawned on me that maybe it would be possible to just move the tank?
          2020 GD 320G
          2021 Ram 3500 H.O. SRW.

          Comment


          • #20
            Originally posted by RoyB View Post
            Do you guys think it would be possible to move the fresh water tank to the front of the axles? I am talking to my camper dealer about selling off the 320G and purchasing a 351M, but then it dawned on me that maybe it would be possible to just move the tank?
            You would have to drop the coroplast and see what is under that area. It would be possible to do this if there in no items in that area that could not be moved.

            Brian
            Brian & Michelle
            2018 Reflection 29RS
            2022 Chevy 3500HD

            Comment


            • #21
              Originally posted by RoyB View Post
              Do you guys think it would be possible to move the fresh water tank to the front of the axles? I am talking to my camper dealer about selling off the 320G and purchasing a 351M, but then it dawned on me that maybe it would be possible to just move the tank?
              You'd have to be a wizard to pull this off, RoyB. Almost anything is possible given enough time, money, and persistence. Not sure I'd want to try it, and I like doing mods.

              If the 351M fits the bill...IMHO get the right trailer for your needs and press. This is what I did with my TV. Traded a (beautiful!) new 2017 F-250 for the current (used) '17 F-350 DRW. The $5K I lost in the whole process (versus getting the DRW in the first place) was a painful "life lesson", but it was the right move and in retrospect glad I did it.
              Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

              2017 Ford F-350 DRW, '19 315RLTSPlus

              Comment


              • #22
                Originally posted by howson View Post

                You'd have to be a wizard to pull this off, RoyB. Almost anything is possible given enough time, money, and persistence. Not sure I'd want to try it, and I like doing mods.

                If the 351M fits the bill...IMHO get the right trailer for your needs and press. This is what I did with my TV. Traded a (beautiful!) new 2017 F-250 for the current (used) '17 F-350 DRW. The $5K I lost in the whole process (versus getting the DRW in the first place) was a painful "life lesson", but it was the right move and in retrospect glad I did it.
                I rented an F250 once when my Ram was getting some work done. This was when I had my ~8000 lb travel trailer. That trailer pushed the F250 around pretty bad. F250 is very soft for an HD truck. When hooked up to my Ram 2500 I didn't even know it was back there.

                I now have a SRW 3500 on order since the 2500 is a little soft at times. I am hoping I don't kick myself in a few years for not getting a DRW.
                2020 GD 320G
                2021 Ram 3500 H.O. SRW.

                Comment


                • #23
                  Just an update, I emailed GD customer service about if it was possible to move the fresh water tank or upgrading the axles. This was their response.

                  Our apologies for the delay in response. I do appreciate your concern about your weight concerns on your Momentum 320. The 351 M has a Longer D/S slide so the rams on the frame are further apart. There is no room to relocate the water tank on the 320G,so that is why it is located there.

                  In your request about adding larger axles, we do not recommend doing that. If you add larger axles and then put more weight in the RV, over time it is likely it will affect the main frame and cause frame camber issues.


                  I don't think I can recommend this trailer to anyone knowing what I know now.
                  2020 GD 320G
                  2021 Ram 3500 H.O. SRW.

                  Comment


                  • #24
                    Originally posted by RoyB View Post
                    Just an update, I emailed GD customer service about if it was possible to move the fresh water tank or upgrading the axles. This was their response.

                    Our apologies for the delay in response. I do appreciate your concern about your weight concerns on your Momentum 320. The 351 M has a Longer D/S slide so the rams on the frame are further apart. There is no room to relocate the water tank on the 320G,so that is why it is located there.

                    In your request about adding larger axles, we do not recommend doing that. If you add larger axles and then put more weight in the RV, over time it is likely it will affect the main frame and cause frame camber issues.


                    I don't think I can recommend this trailer to anyone knowing what I know now.
                    I agree with you on that comment. We , moderators , have been in contact with GD on this issue and have not really received any info to help you out. It is unfortunate that the design was made as such an owner can not load the trailer for the usage intended.

                    Brian
                    Brian & Michelle
                    2018 Reflection 29RS
                    2022 Chevy 3500HD

                    Comment


                    • #25
                      At this point I think I am just going to cut my losses and move onto a different model or different brand.
                      2020 GD 320G
                      2021 Ram 3500 H.O. SRW.

                      Comment


                      • #26
                        Also, do any of the moderators know the actual overall length of the 351M? I measured my 320G to a couple inches over 38'.
                        2020 GD 320G
                        2021 Ram 3500 H.O. SRW.

                        Comment


                        • #27
                          Originally posted by RoyB View Post
                          Also, do any of the moderators know the actual overall length of the 351M? I measured my 320G to a couple inches over 38'.
                          I've never taken a tape measure to a 351M, but I can tell you the drawing for the unit shows 40' 4" overall from tip to tail. This was as of Feb '18. I doubt it's changed.
                          Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

                          2017 Ford F-350 DRW, '19 315RLTSPlus

                          Comment


                          • #28
                            Originally posted by RoyB View Post
                            Also, do any of the moderators know the actual overall length of the 351M? I measured my 320G to a couple inches over 38'.
                            Curtis OffToHavasu bought a new 2020 351 a few months ago. Hopefully Curtis will chime in with this as I'm sure he has measured (or will do so for you.) You may want to PM him as well.

                            Thanks, in advance Curtis !

                            Dan
                            Dan & Carol
                            2014 303RLS Reflection #185 (10/2013 build)
                            2012 Silverado LTZ Crew Duramax 2500HD - 2700/16K Pullrite Superglide

                            Comment


                            • #29
                              Originally posted by Canyonlight View Post

                              Curtis OffToHavasu bought a new 2020 351 a few months ago. Hopefully Curtis will chime in with this as I'm sure he has measured (or will do so for you.) You may want to PM him as well.

                              Thanks, in advance Curtis !

                              Dan
                              Just about 40'8"
                              Curtis, Christine, Cole, and Charlotte
                              2007 Chevrolet Silverado Duramax LBZ, CCLB
                              2020 Momentum 351M
                              2004 Essex Vortex

                              Comment


                              • #30
                                So someone commented on my thread from another forum today. Apparently GD has now added the option to upgrade for 8K lb axles with disk brakes to the 320G for a reasonable $5K.

                                This has me scratching my head since customer service told me they don't recommend doing this. How is it different now that GD has the factory option to do this? Is this something that I can hire GD to do to my trailer now that it's an option?

                                2020 GD 320G
                                2021 Ram 3500 H.O. SRW.

                                Comment

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