GT 27FB Twin Cargo Capacity Challenges. Need Help!!

[foobar]

Introduction: Newbie to the RV lifestyle, but lived in a 21ft travel trailer full time for 5 years during college (1980-1985) and owned a 28ft sailboat for 15 years. So I'm not completely ignorant about portable living :-)

Have a 2022 Globetrotter 27 FB Twin on order. Manufacturing starts today 4/18/2022 (Yay! ). Hope to take possession sometime in late June or early July 2022.

Tow Vehicle will be 2016 Porsche Cayenne S. Yeah, I've read the 1200 posts in the epic Cayenne, Audi Q, VW Tuareg towing thread, but that's not why I'm engaging the experts here (self declared and otherwise ).

The topic of the day is Globetrotter carrying capacity (or the lack thereof).

Goal: I want to be able to install a 1200ah LiFePO4 battery bank, 3KVA inverter, ~800W of solar, and also have Ultimate Airstreams install their Grand Lounge+Custom Cabinet+wardrobe upgrade and still have a budget left over for the weight of any personal gear I might need (such as food, clothing, fresh water, folding chairs, gas grill, etc, etc).

Now for some math. The information below comes from a photo of the factory supplied sticker on the side of a GT 27FB Twin that is identical to the one I have ordered (i.e. same options, same floorplan). This information "is not" from the factory brochure.

GVWR = 7600lbs

GAWR Front = 3800lbs
GAWR Rear = 3800lbs

So, GVWR = 2 * 3800lbs = 7600lbs (as it should be)

The dry weight of the trailer as manufactured with factory installed options (w/2nd A/C, battery, propane, etc) = 6674 lbs.

The max cargo rating on sticker = 926lbs. This is exactly = GVWR - dry weight = 7600lbs - 6674 = 926lbs. This is also exactly correct.

Note:
Fresh water tank = 39 gallons * 8.3lbs/gallon = 324 lbs
Grey water tank = 37 gallons * 8.3lbs/gallon = 307 lbs
Black water tank = 39 gallons * 8.3lbs/gallon = 324 lbs

Let's assess a few trailer load scenarios:

Load scenario #1:
If someone is forced to travel with all 3 tanks full for some reason, the total weight would be 955lbs.

This would exceed the GVWR of the trailer "without" any additional owner cargo (food, clothing, kitchen equipment, camping chairs, portable gas grill, etc)

Load scenario #2:
Only the fresh water tank is full = 324lbs
New lithium battery bank (four 300ah LiFePO4) batteries = 83lbs/battery * 4 batteries = 332lbs
inverter + solar cells + heavy wiring would be additional weight on top of the battery weight
Planned Seating and cabinetry upgrades = ~300lbs

Total is much greater than 956lbs without including any owner food, clothing, kitchen equipment, camping chairs, portable gas grill, etc.

Scenario #3:
Fresh water tank is full = 324lbs and no other modifications.
That would leave 926lbs - 324lbs = 602lbs for owner gear.

Only scenario 3 works within the safety rating published via the sticker on the side of the trailer, and even it doesn't leave much room for gear (600lbs or so give or take).

Scenario #1 with a reasonable set of owner gear on board would be prohibited within the weight rating documented by the sticker on the side of the trailer. And I know for sure that there are times when owners have to drive with all tanks full and then dump at their destination or somewhere along the way.

AXLE UPGRADE:

So, I started thinking that an axle upgrade was in order since the GVWR is being defined by the GAWR * 2 (for dual axle trailer) = 3800lbs * 2 = 7600lbs.

I spent quite a bit of time studying Dexter's catalog this weekend.

#10 axles are available with a weight rating range of 2300-4000lbs.

#11 axles are available with a weight rating of 4100-6000lbs.

With a published GAWR on the sticker attached to the Airstream = 3800lbs, the logical conclusion is that the 27 FB Twin GT is using a #10 axle.

So, I contacted the dealer to find out if Airstream could upgrade the axle for me during manufacturing.

I expected the answer to be "No" and I wasn't disappointed as that was their exact reply .

What I didn't expect was that the Airstream contact indicated that all Globetrotters that are dual axle (e.g. >=25ft in length) use #11 axles.

Huh?

I ended up talking on the phone with someone from Airstream (I didn't ask if it was ok to use his name in this thread, so I'll refer to him as the "Airstream Guy").

We went round and around on the topic on the phone.

The Airstream Guy said that they are definitely using #11 axles on dual axle trailers and have many trailers on the road for many years without any problems. My position is that information is irrelevant. What matters is what the GVWR is and the measured dry weight of the trailer plus the weight of the load that the owner puts in the trailer. If the dry weight + owner gear weighs more than GVWR, then it's game over.

GVWR for GT 27 FBT = Axle weight rating * 2 (for dual axle trailers) = 7600lbs, so the axles are definitely determining the GVWR weight rating based on the math at the top of the email above.

The Airstream Guy was confident that Globetrotters that are dual axle (25ft and above) are using Dexter #11 axles and that Airstream is using an intentionally conservative rating. He doesn't know what the actual GAWR rating is for the #11 axle that is installed, but is relying on the axle weight range that Dexter puts in their catalog = 4100 to 6000lbs to try and reassure me that everything is going to be ok. Well, I know for a fact that Dexter will custom fabricate axles with lower weight ratings than the ranges published in their catalog for a given axle (e.g. #10 vs #11, etc). So I can't really rely on fuzzy assurances from the Airstream Guy (no offense intended) that the axles are definitely #11 and have at least 4100lb GAWR per axle. And, I really need to know what the exact GAWR rating is for each axle.

I have a hard time with this argument given how much prospective owners scrutinize GVWR in order to choose the right trailer for their tow vehicle limits and intended owner loads. If they were conservative in their published ratings, they become less competitive in the marketplace for RV's.

So, my next challenge is to find someone that has access to a 2022 globetrotter 27 FB twin and take pictures of the Dexter axle serial number and any other markings or stickers on the axle so that I can call up Dexter and find out which axle is on the trailer and what the exact GAWR is.

If you own a GT 27 FBT could you please post the information requested above along with a photo of the weight rating sticker on the side of the same trailer?

I also need to know what tires are installed (the manufacturer, model, and max speed and weight ratings) as those can be limiting factors too.

This is definitely a safety issue.

As you can tell, I'm an Engineer and I firmly believe that the numbers really do matter :-) As does anyone who happens to be on a bridge when it collapses due to a misplaced decimal somewhere.

Can any of the current owners chime in and help gather the axle and tire information requested above? Thanks in advance.

Please be gentle, this is my first posting on airforums

[Rich Jenkins]

Originally Posted by foobar

So, my next challenge is to find someone that has access to a 2022 globetrotter 27 FB twin and take pictures of the Dexter axle serial number and any other markings or stickers on the axle so that I can call up Dexter and find out which axle is on the trailer and what the exact GAWR is.

Welcome to Airforums.

In case it helps, I found the attached information in the 2021 Airstream Globetrotter Parts Book (latest available online). It lists three Dexter axle part nos. for the '21 GTs (23FB, 25/27FB and 30RB) on page I-40. The one for the 27FB appears to be labeled as a "3,800 LB" axle.

Some additional information for the Dexter 410980-02 is at the below link.

https://highskyrvparts.com/new-airst...axle-410980-02

[foobar]

Originally Posted by Llando88

Welcome to Airforums.

In case it helps, I found the attached information in the 2021 Airstream Globetrotter Parts Book (latest available online). It lists three Dexter axle part nos. for the '21 GTs (23FB, 25/27FB and 30RB) on page I-40. It appears to be labeled as a "3,800 LB" axle.

Some additional information for the Dexter 410980-02 is at the below link.

https://highskyrvparts.com/new-airst...axle-410980-02

Thanks Lando88!. That helps. I'll follow the link you provided and dig into it a bit further.

[foobar]

According to the Dexter catalog, 12inch brakes are only present on #11 Axles, so that's one positive bit of news.

The #10 axles use 10inch drum brakes.

But, the same catalog says that #11 axle weight ratings start at 4100lbs and can be with up to 6000lb ratings.

It's starting to look like Airstream might have installed a downrated axle (perhaps for a softer ride?). I'll try and find out from Dexter.

Would be great if an owner of a 2022 27 FB Twin Globetrotter could provide whatever information Dexter puts on the axle in case Airstream made any Axle changes between 2021 and 2022. I don't think so based on GVWR remaining the same, but would be best to find out for sure.

[Rich Jenkins]

Originally Posted by Llando88

Welcome to Airforums.

In case it helps, I found the attached information in the 2021 Airstream Globetrotter Parts Book (latest available online) ...

The 2022 GT parts book now appears to be released (I last checked a few months ago for my 2022 23GT, and I could only find the 2021 parts book):

https://www.airstream.com/wp-content...Parts-Book.pdf

There are no changes in part numbers for the axles listed on page I-40.

[Rich Jenkins]

Originally Posted by foobar

Thanks Lando88!. That helps. I'll follow the link you provided and dig into it a bit further.

No problem.

Got a question for you.

Why does it matter what axle is on the trailer now if you are going to replace it? Why aren't you starting with the requirements for your max load trailer weight you desire, and figuring out what axle you need?

[foobar]

Originally Posted by Llando88

No problem.

Got a question for you.

Why does it matter what axle is on the trailer now if you are going to replace it? Why aren't you starting with the requirements for your max load trailer weight you desire, and figuring out what axle you need?

Gracias Amigo.

I started with the assumption that an axle rated for 3800lbs would be a #10 axle. A #10 axle is limited to a max GAWR = 4000lbs.

So I was planning to upgrade the Axles and was assessing what Axle down angle + lift kit rise and GAWR I wanted to specify for the new axles.

But when my dealer contacted Airstream and the Airstream rep insisted that a #11 axle was being used and no upgrade would be necessary, I started down the path of determining if this is really true. I.e. that #11 axles are being utilized by the factory (this appears to be true) and that the GAWR would therefore be at least 4100lbs per axle based on the Dexter catalog (this doesn't appear to be true, but further investigation is required).

If the axles are capable of at least 4100lbs each, then I would gain 600lbs in trailer GVWR. That might be enough to prevent needing new Axles, which would probably save me at least $5k in parts and labor.

[foobar]

Just got off the phone with Dexter.

410980-02 is the Airstream part number unfortunately and they can't do anything with that information.

What they said would help is to get a serial number from another 27 FB Twin Globetrotter so that they could look it up in their system.

The serial number is a 9 to 12 digit number that will be etched into the rear surface of the center of the axle tube or can also be present on a white sticker on the forward surface of the center of the axle.

Can someone that already owns one of these puppies please take a photo of the front and rear surfaces of the center of one of the axle tubes? I would greatly appreciate it.

[GRadventures]

I am not an engineer so please excuse my ignorance if this is a dumb question. How do you account for the 900# (plus or minus) of tongue weight moving to the TV and is not on the trailer axles?

[foobar]

Originally Posted by GRadventures

I am not an engineer so please excuse my ignorance if this is a dumb question. How do you account for the 900# (plus or minus) of tongue weight moving to the TV and is not on the trailer axles?

GRadventures, it's a good question.

Without a WD hitch, the trailer tongue weight pushes down very hard on the hitch ball some distance behind the rear wheels of the two vehicles. This causes the weight on the front wheels of the tow vehicle to reduce by hundreds of lbs. Think of a playground teeter totter. The trailer tongue weight is pushing down on one end of the teeter totter and the tow vehicles body (or frame) acts like the plank of wood on the teeter totter while the rear axle of the tow vehicle is the pivot point. The weight of the tongue is forcing the front of the tow vehicle to rise up, making it difficult to maintain adequate braking and steering capabilities.

The WD hitches use torque to transfer force. In this case it is using torsion bars on the hitch to pull up on the tow vehicle hitch ball (this can be thousands of ft-lbs) causing to extra downward force on the front wheels of the tow vehicle and "also" extra downward force on the travel trailers axles.

Some people describe this as transferring weight off of the tongue of the trailer (and off of the rear axle of the tow vehicle) onto the front axle of the two vehicle and onto the travel trailer axles. That's not technically accurate from a physics professors point of view, but from a practical standpoint, given that the force of gravity causes things to have what we call weight, having extra forces pressing down on the TV front axle and the TT axle will look exactly like the these two axles have gained "weight" if you go visit a truck scale and look at all of the axle weights before and after the application of the WD hitch capabilities.

In summary, the WD hitch will act like it is transferring some of the tongue weight to the tow vehicle's front axle and the travel trailer's axles while appearing to reduce the perceived weight of the tongue and the weight on the tow vehicles rear axle.

So, having said the above, you have caught an error in my calculations. I needed to add the transferred force (i.e. weight) that the WD hitch will put on the axles of the trailer. I'll have to go rooting around for the rules of thumb on the percentage of weight transfer to the various axles. Does anybody recall those off the top of your head?

GRadventures, I'm probably not the best at describing this so I hope this helped and didn't muddy things up worse in your mind :-)

[foobar]

Originally Posted by foobar

GRadventures, it's a good question.

Without a WD hitch, the trailer tongue weight pushes down very hard on the hitch ball some distance behind the rear wheels of the two vehicles. This causes the weight on the front wheels of the tow vehicle to reduce by hundreds of lbs. Think of a playground teeter totter. The trailer tongue weight is pushing down on one end of the teeter totter and the tow vehicles body (or frame) acts like the plank of wood on the teeter totter while the rear axle of the tow vehicle is the pivot point. The weight of the tongue is forcing the front of the tow vehicle to rise up, making it difficult to maintain adequate braking and steering capabilities.

The WD hitches use torque to transfer force. In this case it is using torsion bars on the hitch to pull up on the tow vehicle hitch ball (this can be thousands of ft-lbs) causing to extra downward force on the front wheels of the tow vehicle and "also" extra downward force on the travel trailers axles.

Some people describe this as transferring weight off of the tongue of the trailer (and off of the rear axle of the tow vehicle) onto the front axle of the two vehicle and onto the travel trailer axles. That's not technically accurate from a physics professors point of view, but from a practical standpoint, given that the force of gravity causes things to have what we call weight, having extra forces pressing down on the TV front axle and the TT axle will look exactly like the these two axles have gained "weight" if you go visit a truck scale and look at all of the axle weights before and after the application of the WD hitch capabilities.

In summary, the WD hitch will act like it is transferring some of the tongue weight to the tow vehicle's front axle and the travel trailer's axles while appearing to reduce the perceived weight of the tongue and the weight on the tow vehicles rear axle.

So, having said the above, you have caught an error in my calculations. I needed to add the transferred force (i.e. weight) that the WD hitch will put on the axles of the trailer. I'll have to go rooting around for the rules of thumb on the percentage of weight transfer to the various axles. Does anybody recall those off the top of your head?

GRadventures, I'm probably not the best at describing this so I hope this helped and didn't muddy things up worse in your mind :-)

I might have this wrong, but I recall that after you have tuned up your WD hitch properly, you will end up with 1/3rd of the tongue weight on the tow vehicle front axle, another 1/3rd on the tow vehicle rear axle and the final 1/3rd on the axles of the trailer.

In my case, the additional downward force placed on the pair of GT 27 FB Twin's axles will be about half of the final tongue weight (estimated to be about 1000-1100lbs fully loaded). So 600-633lbs or so will end up on the tow vehicle axles (300-316lb or so per axle) and 300-316 lbs on the trailer axles (i.e. approximately 150-158lbs per trailer axle)

So we would need to add another 300-316lbs to each of the trailer load scenarios that I described in the original posting. As far as I can tell, the Globetrotter airstreams have some real concerns with respect to the Airsream's GVWR and the related safety concerns. This is independent of the tow vehicle, so please don't tell me this problem is solved by buying a F250 or F350

[Bill M.]

Almost all of the tongue weight is going to be carried by the TV. Particularly if a short wheel base SUV is the TV. Maybe 100 lbs or less of the tongue wight will be transferred back to the trailer axles. Our trailer is rated for 6800 lbs gross and 6400 lbs axle rating. It actually puts 800 lbs on the truck when hitched and about 5700 on the axles when we travel.

Figure on doing your main traveling with 1/4 to 1/2 full fresh water and empty gray and black tanks. Fill up all the way when close to the boon docking area, Carry a cheater attachment for a campground faucet and a long hose. If you have to run over weight for a while because of all the tanks are full just slow down.

[1StreamDream]

Although not specific to the axle rating discussion, for the purpose of your researching how to increase the load carrying capability of your trailer, do not lose sight of the tires and the rating of them. I believe that Airstream ships from the factory with load range "D" tires, probably to provide the softest ride, but many folks move up to load range "E" tires, they can carry more weight, but as they have stiffer sidewalls to enable that load carrying, they also have a stiffer ride. This might be part of the explanation on why the overall GVWR is less than you expect it should be based on catalog info for the axles. There should be a tire rating sticker on the trailer, in the same area where you found the axle rating and GVWR, that will be the definitive answer for an individual trailers factory rating.

[foobar]

Originally Posted by Bill M.

Almost all of the tongue weight is going to be carried by the TV. Particularly if a short wheel base SUV is the TV. Maybe 100 lbs or less of the tongue wight will be transferred back to the trailer axles. Our trailer is rated for 6800 lbs gross and 6400 lbs axle rating. It actually puts 800 lbs on the truck when hitched and about 5700 on the axles when we travel.

Figure on doing your main traveling with 1/4 to 1/2 full fresh water and empty gray and black tanks. Fill up all the way when close to the boon docking area, Carry a cheater attachment for a campground faucet and a long hose. If you have to run over weight for a while because of all the tanks are full just slow down.

Good point on managing the fresh water load, but it seems to me that Airstream should have upped the spec in the axle GAWR to increase the max GVWR. The current setup seems inadequate to me. Or at least in terms of how I plan to use the trailer (to be fair) :-)

[foobar]

Originally Posted by 1StreamDream

Although not specific to the axle rating discussion, for the purpose of your researching how to increase the load carrying capability of your trailer, do not lose sight of the tires and the rating of them. I believe that Airstream ships from the factory with load range "D" tires, probably to provide the softest ride, but many folks move up to load range "E" tires, they can carry more weight, but as they have stiffer sidewalls to enable that load carrying, they also have a stiffer ride. This might be part of the explanation on why the overall GVWR is less than you expect it should be based on catalog info for the axles. There should be a tire rating sticker on the trailer, in the same area where you found the axle rating and GVWR, that will be the definitive answer for an individual trailers factory rating.

1StreamDream, good point. I think I might have mentioned that I need to find out what the tire ratings are too, but thanks again for the reminder. Hopefully someone that has this trailer can help here.

[jeffmc306]

Originally Posted by foobar

Just got off the phone with Dexter.

410980-02 is the Airstream part number unfortunately and they can't do anything with that information.

What they said would help is to get a serial number from another 27 FB Twin Globetrotter so that they could look it up in their system.

The serial number is a 9 to 12 digit number that will be etched into the rear surface of the center of the axle tube or can also be present on a white sticker on the forward surface of the center of the axle.

Can someone that already owns one of these puppies please take a photo of the front and rear surfaces of the center of one of the axle tubes? I would greatly appreciate it.

Foobar, if it helps here’s a photo from our 2019 27’ GT’s axle. I crawled underneath when we got it and snapped photos of all the tags.

According to this, it’s a 3800 lbs capacity. Serial number is listed.

[Fungus]

Originally Posted by foobar

Load scenario #2:
Only the fresh water tank is full = 324lbs
New lithium battery bank (four 300ah LiFePO4) batteries = 83lbs/battery * 4 batteries = 332lbs
inverter + solar cells + heavy wiring would be additional weight on top of the battery weight
Planned Seating and cabinetry upgrades = ~300lbs

Are these numbers net of the gear that is coming out?

Lithium goes in. What comes out?

[Colossus]

Originally Posted by jeffmc306

Foobar, if it helps here’s a photo from our 2019 27’ GT’s axle. I crawled underneath when we got it and snapped photos of all the tags.

According to this, it’s a 3800 lbs capacity. Serial number is listed.

Additionally that 3800 per axle matches up with the 7600 maximum trailer capacity on the brochure.

Great idea of crawling under the unit and snapping pictures of all the tags. Looks like I have a chore to do this weekend.

[Hans627]

While attending the International Rally in Lebanon, TN last summer I talked to the Dexter representative. Very informative. Not sure if he will be in ME this year or not. He said if I send him the serial number of my axle he will give me the specs, which he did. Here response:

Hi Bob,

Please find attached your axle information. A very good axle combination, our heavy #11 axle tube, hubs, and Nev-R-Lube bearings, with a 3800 pound suspension for a good ride. It also has Never-Adjust Brakes. The only maintenance it requires is periodic inspection of the brakes for wear and lubrication of the pivoting and adjusting mechanism of the brakes.

Thanks for participating with us at the Lebanon rally.

Hope to see you in Maine next year!

Bill

[foobar]

Originally Posted by jeffmc306

Foobar, if it helps here’s a photo from our 2019 27’ GT’s axle. I crawled underneath when we got it and snapped photos of all the tags.

According to this, it’s a 3800 lbs capacity. Serial number is listed.

Thanks jeffmc306. I can confirm that your Airstream part number410980-02 is the same as the one on a 2021 and 2022 27 Globetrotter FB series.

I got an axle serial number from another source earlier this morning and called Dexter. I'll transcribe my notes into an updated posting in a few minutes. Stay tuned.