Undersized axles on Momentum 320G or just poor design?

[Guest]

They do but the one ton spring pack may be positioned to transfer some mass to the front. Airbags will allow some minor shifting if the vehicle is pitched to the front but otherwise they just level the tow vehicle.

I am in no way proposing to add one ton springs to try and gain payload but rather just making some comparisons as to why the SWR truck handles so poorly. We have seen some verbiage that the trailer may be nose high. Was the trailer nose high on the DRW truck? The other thought is side flex on the tires on the SRW truck. Since the OPs truck looks to be overloaded, a properly equipped one ton DRW truck is the fix based on the comparison tests.

Jim

[chikenstiker]

Joseph may have something here on the lack of the one ton spring pack. Even though the bags are there. It would still be nice to see a side pic of the SRW truck with the rig attached.

Jim

With 55-65 psi in air bags the truck sits perfectly lever with front having a 2" leveling kit. So ~1" sag off the overloads.

Guest Airbags are tied together as i didn't want to have to fill them separately. Yes tied together theoretically can have less sway support, but the tiny little hose doesn't flow that much either.

Buddies truck is older gen F350 and his air bags (tied together) takes the trailer off the Overloads at 55 psi I had him use.

[chikenstiker]

They do but the one ton spring pack may be positioned to transfer some mass to the front. Airbags will allow some minor shifting if the vehicle is pitched to the front but otherwise they just level the tow vehicle.

I am in no way proposing to add one ton springs to try and gain payload but rather just making some comparisons as to why the SWR truck handles so poorly. We have seen some verbiage that the trailer may be nose high. Was the trailer nose high on the DRW truck? The other thought is side flex on the tires on the SRW truck. Since the OPs truck looks to be overloaded, a properly equipped one ton DRW truck is the fix based on the comparison tests.

Jim

Trailer is nose high a bit on my truck. Rear of my truck is stock except one size larger tires and if I lower the hitch anymore I'll be hitting the bed rails. I have right about 6" clearance.

Buddies F350 DRW has a Lift and 35" tires so my trailer was even higher in the front. I'd guess his truck raised the front of my trailer almost 2" and I only had 5" of bed clearance at best. So, if anything it should have rode worse on his truck being higher.

He has 35" tires on 20" rims, I have 34" tires on 18" stock rims (stock tires were 33.5" I think.) So I have ~1/2" more sidewall to flex? Tires are E rated. Trailer tires were at 120 psi for both runs.

[Guest]

We may never know why the DRW helps in your case but we do know what corrects the issue. A DRW truck.

Jim

[espayne]

We took our 320G fully loaded leaving Yuma AZ going to Moab Ut. Got on the freeway and as soon as I got above 58 mph it would sway a lot. Semis passing was a white knuckle experience on the interstate. Got to Flagstaff and changed the height of the Curt A20 hitch to the lowest position. Clearance is about 4 1/2 inches now. Moved less 50 pounds forward to the bed and from there continued north. For some reason it was enough to where I was able to travel at 62 mph and no semi sway issues up and back. Got better as more water was transferred to the black and gray tanks on the way back. Pin weight is a real issue with this Fifth wheel. Not sure if we are going to be able to trust this 320G going boondocking as I know the axles are running overweight when loaded up. Just took a trip without the CanAm and it is a great ride 70 mph very stable. My truck is a 21 Ram 3500 8ft bed SRW. What I have learned so far is get as much weight up front on the pin and as little in the rear.

[Villager]

We took our 320G fully loaded leaving Yuma AZ going to Moab Ut. Got on the freeway and as soon as I got above 58 mph it would sway a lot. Semis passing was a white knuckle experience on the interstate. Got to Flagstaff and changed the height of the Curt A20 hitch to the lowest position. Clearance is about 4 1/2 inches now. Moved less 50 pounds forward to the bed and from there continued north. For some reason it was enough to where I was able to travel at 62 mph and no semi sway issues up and back. Got better as more water was transferred to the black and gray tanks on the way back. Pin weight is a real issue with this Fifth wheel. Not sure if we are going to be able to trust this 320G going boondocking as I know the axles are running overweight when loaded up. Just took a trip without the CanAm and it is a great ride 70 mph very stable. My truck is a 21 Ram 3500 8ft bed SRW. What I have learned so far is get as much weight up front on the pin and as little in the rear.

Really sorry to hear about these sway / white-knuckle experiences. Our 2021 320G w/ 8,000 lb axles has towed extremely well - particularly after adding 500 lbs to the front area of the trailer. We put about 6,000 miles on the camper this past summer and fall. Typically tow at 65 MPH with our 3500 Ram SRW short bed, but on occasion have gone well in to the 70s. No swaying issues. 600 lb motorcycle in back. Usually about 1/2 tank of fresh water, but have also towed with a full tank. GVW close to 16,000. Pin weight percentages have ranged from 15% to 18.5%. We don’t have the 3rd A/C or patio kit, but do have the three season doors and second awning in the back. Yes, getting weight forward is a good thing!

[chikenstiker]

We took our 320G fully loaded leaving Yuma AZ going to Moab Ut. Got on the freeway and as soon as I got above 58 mph it would sway a lot. Semis passing was a white knuckle experience on the interstate. Got to Flagstaff and changed the height of the Curt A20 hitch to the lowest position. Clearance is about 4 1/2 inches now. Moved less 50 pounds forward to the bed and from there continued north. For some reason it was enough to where I was able to travel at 62 mph and no semi sway issues up and back. Got better as more water was transferred to the black and gray tanks on the way back. Pin weight is a real issue with this Fifth wheel. Not sure if we are going to be able to trust this 320G going boondocking as I know the axles are running overweight when loaded up. Just took a trip without the CanAm and it is a great ride 70 mph very stable. My truck is a 21 Ram 3500 8ft bed SRW. What I have learned so far is get as much weight up front on the pin and as little in the rear.

We were ready to get rid of the trailer. But after towing it with a DRW, I am thinking I'd rather spend 10-20 k upgrading my truck than lose 15-20 k on my trailer trying to sell it? All we do is boondock as well and I need the water. I'll probably ditch the patio kit shuffle a few other things around and get a DRW and call it a day.

But downgrading back to a Tow behind isn't completely off the table.

Speed as you mentioned does make a difference, I find it increases dramatically 60 and over and I often tow at 65ish.

[Wileykid]

Last time I weighed my 320G, it had a 17.4% pin weight, with some water in the grey tank. I have been putting more water in the grey tank, and think I am around 18% now. My usual speed is around 65-67 mph, but have made several dashes up to about 75 mph without any sway. GD should have maybe split the fresh water tank so they could fit one forward of the axles. Either way, it is all about the pin weight. Makes it difficult for people like Chikenstiker who it is not good to carry water in the grey tank to a campsite.

I have not pulled the underside, I sure hope the grey tank is mounted properly, and I don't see it hanging or gone on a trip.

[espayne]

When the 320g was fully loaded it weighed in at 16780 lbs. with hitch pin weight of 2000 lbs making that 8.39% pin percentage. That is a awful percentage from what I have read on these forums. I am a rookie at this but getting educated very quickly about what is good and bad.

[chikenstiker]

Mine was 16,820 with a Pin of 14.7% (2,480) and I was 1 dirtbike shorter than usual, but a few extras in front and back.

IF I add water to the Grey, 1) I will be overloaded by even more and 2) have to dump and make a mud hole where I'm parked and 3) waste water in a drought.

We're most likely buying a Dually and I'll drop some weight off the back of the trailer and call it a day it made that much difference. The other alternative is to dump the trailer, lose money and go back to a tow behind, but I like the trailer otherwise. We spent A LOT of time searching and researching to pick this one.

[chikenstiker]

UPDATE:

This is for anyone following this thread or who stumbles upon it also having troubles with the Grand Design 320G. A Lot has happened since December.

I bought a Ram 3500 Dually in December and it mitigated a majority of the sway! I no longer drive White Knucked and worry a little less about how I load it. BUT, i still have a few issues.

- I still have some sway (was always told 5th wheels don't sway)
- The porpusing is horrendous, especially going over railroad crossings or bad bridges, sometimes the whole trailer bounces the truck so hard you think it's going to break something. I say this is because of the light Pin which makes the trailer to balanced and teetering.
- The trailer still has a very light Pin for a 5th

I've been working with the dealer and they have been going back and forth with Grand Design and Lippert who keep telling them there is no issue and they don't understand how I can get these Pin weights. I'm like light Pin from factor, toys in garage = DUH!

Grand Design/Lippert has had me:

- Weight my trailer multiple time on MY Dime $$$
- Mad me empty my entire trailer except kitchen, fill water, gas and propane and weigh again
- Made me bring trailer to dealer just to measure axles specs and placement
- Lost those measurement and made me bring it in again for measurement (trailer 80% full)
- Empty Water, fill Grey, Add weight to Front as much as possible tow and see if any better
- Now they want me to Fill trailer completely like I'm going away for a week and take to dealer to measure everything a 3rd time...

Observations compared to other models:

- the GD 349/351 have the same wheel to rear measurement as the 320, but the front is 2.5' longer...

From Factory Pin was like 14%
Heavy Trip Pin was 14.7%
Emptied out except kitchen Pin was only 14.9%

I don't see how others don't have these problems, either there is something wrong with my rid or they just don't use the garage for toys. I can't imagine a 2000lbs SXS let alone it'd put me over axel ratings...

And now I got an out of office reply about my Friday measurements that my dealer contact no longer works there. So will I have to start all over?

[Wileykid]

Thanks for all the work you have done with the weight, and trying to get GD to acknowledge it.

I am on a trip, and weighed my trailer after a fuel stop. With 20 gallons of water in the grey tank, 5 gallons of fresh, 3 cases of water under the bed, and my 500 lb motorcycle, I am at 18% pin weight. Also should add, that the Sidewinder hitch I have, is about 150 lbs heavier than the stock one. I don't have sway that I can tell, and comfortable driving with only one hand on the wheel.

I use to have a small amount of porpoising, but got rid of most of it when I added Bilstein shocks, and Timbren springs to the truck. There was a section of the 81 in New York, that I did get bad enough porpoising that I had to slow down to about 50 mph. The road was that bad, felt like I was on a bronco, was going to break the hitch, and at the first rest stop, stopped and checked everything, including to see if my bike was okay (it was).

I am under all max weights per the CAT scale. 620 lbs under max rear axle weight.

[chikenstiker]

Thanks Wileykid!

Most the places I camp I'm 45 minutes plus from where I can fill up on water and usually traveling in late afternoon evening and really don't want to stop to fill up on questionable water.

In my garage 3 dirtbikes and chairs and whatnot is ~1200 Lbs

I used to have about 6 gollons of water under my bed as well but took it out when they made me empty my trailer to weigh it for them again.

Truck has Bilsteins and Factory Air Bags. You can tell the porpusing I get is all railer, the truck is trying to manage it pretty well.

UPDATE:

My Service Manager either left or got let go? So I called the other store to talk to a higher up, they now want me to deal with them. The bad they are 1.5 hours away. The good!!! The lady I spoke with has dealt with a very similar issue, but it was on a Solitude that did have a back garage door. After lots of back and forth with customer and grand design they determined that the customers Pin Box was defective or something to that effect. They had a better quality Pin Box installed and the customers issues were eliminated... Now, this won't affect Pin weight much except any heavier the new Pin Box is, but maybe some of the issues really are coming from a flimsy Pin Box???

Where this makes some sense is 2 things..

1) Wileykid it seems has upgraded his pin box and has less or no issues.
2)Last trip I happened to be looking in my rear view mirror and I noticed that the front of the trailer seemed it was flexing a lot and that the trailer was moving around compared to the bed of the truck, yet the road was fairly flat. When I hit little rises and dips in the road it seemed the bed to trailer clearance was expanding and compressing as if the whole front of the trailer was flexing up and down. It was the first time I had noticed this.

Heading out on a trip in a couple hours and I'll definitely be paying attention to it this trip. What if it was a defective Pin Box this whole time that GD has been stringing me along and for a small warranty part could have helped me out months ago?

[Wileykid]

I would be interested in what they considered a "defective" pinbox. The Sidewinder has a small rubber "cushion" in the pivot area, which I think helps, especially over the stock solid metal pinbox.

Mine also moves around, and is noisy. Rolled the rear window down, and wow, rolled it back up. I attribute it to the suspension on the trailer is no where near as good the truck. The trailer is going to react more to the road, bounce more, where your truck doesn't.

[JBill9694]

I'd be concerned about being able to see the nose "flexing". There should be some deflection of the structural members under load and the amount of deflection will change during travel, but we are talking minor movement. IMO chikenstiker should not be able to see the nose flexing.