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Old 08-13-2015, 04:57 PM   #1
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1979 31' Sovereign
Northeastern , Kentucky
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Why is my 1979 so heavy?

I took an unloaded trip the the CAT scales, with the exception of full propane tanks, full water (50 gals), and 1 battery in each compartment up front. I also have a propride. To my surprise, the weight reading was 6,660 lbs (gross weight of 12,020 - TV weight of 5360). My tongue weight was 700lbs (TV with WD unloaded and a reading of 6060 - TV weight of 5360).

According to Airstream document archives, a 31 ft center bath like mine has a weight of 4,810lbs with a tongue weight of 545lbs.
http://www.airstream.com/wp-content/...3b7c825780.pdf

Per the PDF, the weights stated are for standard equipped models. Changes to my trailer include a real full size mattress in back, and replacement of the furniture up front with a dinette built using 5mm cut sheets and 1x1s. The weight up front is likely less than it was originally. The only other change is replacement of the carpet with laminate flooring, so perhaps a couple hundred pounds extra there.

My tongue weight seems spot on, considering the weight of the propride. However, the trailer weight seems heavy even considering a full tank of water (approx 417 lbs) and full propane tanks (approx 120 lbs).

My trailer weighs 1,850 lbs more than the factory specs. Even with a full tank of water, full propane, laminate flooring, and propride, I'm still probably about 1,000 lbs over Airstream's specified weight.

Fortunately, with weight distribution my trailer axles weighs in at 6,000 lbs (5,960 without WD) and my trailer axle ratings are 3200 lbs a piece, so I've got 400lbs to spare until these axles are upgraded as they're original.

Any idea why my 79 is so heavy relative to the Airstream specs?
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Old 08-13-2015, 06:24 PM   #2
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It may be an Excella dressed like a Sovereign. They weighed almost a ton more than a comparable Sovereign.
Check to see, for example, if you have single or double pane windows throughout.
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Old 08-13-2015, 06:34 PM   #3
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The weights from the factory are for a stripped base model trailer, you have to add in all the optional stuff. Somewhere I have the 1975 manual and it lists all the weights of the options and whether it adds to or subtracts from the tongue weight. I don't know if that exists for the 1979 models or not.

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Old 08-13-2015, 06:34 PM   #4
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Great thought, but I just checked and my windows are all single pane.
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Old 08-13-2015, 06:38 PM   #5
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I wondered about that. What are some things that might be considered optional?
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Old 08-13-2015, 07:18 PM   #6
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1975 31' Sovereign
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Quote:
Originally Posted by KYAirstream View Post
I wondered about that. What are some things that might be considered optional?
Water filters, Vista View windows, central vac, oven, air conditioner, bunks, some furniture, some cabinetry, spare tires, larger LP tanks, there were quite a few things and they varied from year to year. I will see if I can find the list from 1975. It won't be the same, but it will give you an idea. It may also be that the factory just flat missed the number. Somewhere between the late 1970's and the early 1980's they upped the frame rail size by an inch which would have added some additional weight too.

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Old 08-13-2015, 07:23 PM   #7
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I'll check my manual for options and weights...don't have it with me here at the moment.

Do you recall what the increased frame depth was?
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Old 08-13-2015, 07:36 PM   #8
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Also, the GVWR on the trailer says 7100lbs. How does that apply since the axle ratings are both limited to 3200lbs?

Perhaps the listing is incorrect? The tire and PSI listed are load range C at 40PSI, which seems way too low.
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Old 08-13-2015, 07:44 PM   #9
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My understanding is that GVWR includes the tongue weight. So if each of your axles are rated at 3200#, you can have a max weight of 6400# on the axles and another 700# on the tongue, for a total of 7100#.
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Old 08-14-2015, 10:30 AM   #10
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I don't believe the specification page weights are with AS full of water. 50 gallons of water would add about 300#. I may be wrong. Just my 2 cents.
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Old 08-14-2015, 11:13 AM   #11
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I don't believe the factory specs include water either. But even if water, propane, change to laminate floor, and the weight of the propride hitch are factored in, the weight still exceeds factory specs by about 1,000lbs.
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Old 08-14-2015, 11:38 AM   #12
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The GCW (gross combination weight) of my '83 Suburban (3/4 ton) fully loaded and my '77 31 ft Sovereign is 12,400 lbs. So I'd say your GCW is about right.

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Old 08-14-2015, 11:57 AM   #13
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Unloaded the weight of my vehicle and trailer is 12,020lbs. That's with water and propane, but unloaded with regard to any stuff.
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Old 08-14-2015, 02:50 PM   #14
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It all adds up fast. If you need a copy of my 78 option / weight sheet let me know. Should be close.
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Old 08-14-2015, 04:24 PM   #15
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I dug up my manual and found those options and corresponding weights. I calculated almost 700 lbs of options that I have, so that leaves only about 300lbs unaccounted for. Much better than the 1,000 lbs I couldn't explain before. I'm surprised things like the fridge, bal jacks, space locker, spare tire bracket, main step, etc are options and not standard equipment, but that does help explain some of the weight difference.

With a combined axle rating of 6400 lbs, I don't have much room for extra stuff. When I replace my axles can I upgrade them, or does the frame and GVWR of 7100lbs limit me?
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Old 08-14-2015, 04:31 PM   #16
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In review ... from a 1975 owners manual for a 31' center bath double bed, in parenthesis is my explanation

7,100# GVWR Gross Vehicle Weight Rating (total allowable trailer weight)
4,970# factory weight without options or variable weights [separate table - everything from AC to dual pane windows, and all tanks] (how much the trailer itself weighs)
2,130# allowable additional total weight including personal cargo (how much your extra stuff and options can weigh - to include all tanks)
6,400# GAWR Gross Axle Weight Rating (of the 7,100# GVWR, how much is supported by the axles)
4,280# Factory Axle Weight (how much weight is on the axles before adding options or personal stuff)
2,120# allowable additional weight (how much more weight in options and personal stuff - to include fresh, gray, black and propane tanks - the trailer can carry)
690# factory tongue weight without options or variable weights

Different from the above, I found this a useful review for our 75 Overlander which started life as a twin bed rear bath, but a PO removed one of the beds, put in partial full bed cabinetry, and the front goucho is a skeleton frame reminder of its former self. So rough guess is I get maybe another 200# worth of stuff I get to put in it in addition to the 1,600# from the chart. Add up the options and variables ...

weight on
total/axles/tongue
150/128/22 - AC
60/46/13 - stabilizing jacks
66/8/58 - LPG 10 gal alu tanks full
5/2/3 - TV antenna
373/266/107 - fresh water tank full
83/55/29 - water heater 10 gal full
60/78/-18 - waste tank (at rear of trailer so subtracts from tongue weight)

797# total added weight from options and variables
583# of that total added weight on the axles
214# of that added weight on the tongue

So from the approximately 1,800 pounds of stuff I can add to the trailer, only about 1,000 pounds can used if my tanks are full.
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Old 08-14-2015, 04:38 PM   #17
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Why is my 1979 so heavy?

Quote:
Originally Posted by KYAirstream View Post
With a combined axle rating of 6400 lbs, I don't have much room for extra stuff. When I replace my axles can I upgrade them, or does the frame and GVWR of 7100lbs limit me?

Possibly. This would be a good time for Andy or Colin to reply. I seem to remember something about only increasing axle capacity by a certain percentage. This likely has more to do with the rest of the chassis and tongue being stout enough to do the work of an axle of greater capacity.
For example we could modify the suspension at the axles of a Ford Pinto to hold up 10 tons, but when fully loaded and attempting to move it, it will fold like a beer can.
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Old 08-14-2015, 04:42 PM   #18
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1979 31' Sovereign
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Why is my 1979 so heavy?

Have you been to the scales? It'd be interesting to compare your calculated weights to scale weights.

My trailer is 6660lbs with only fluids (water and propane) on board, leaving me with room for only 440lbs of stuff before reaching the GVWR of 7100lbs.
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Old 08-14-2015, 05:06 PM   #19
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No, since we've had it, we haven't taken it to scales. It might be interesting to see how it weighs - actual compared to chart weights - before loading up and heading out of here. Especially since the axles are borderline (slight down decline, only a 2" change when raised instead of 3").

This owners manual has a sample problem for calculating how much of your stuff you can add to a 31' after various variables and options - roughly 1,000#.

One thing I didn't adjust for is the replacement finish floor, and the two extra batteries mounted on the bumper.
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Old 08-14-2015, 05:11 PM   #20
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If you happen to take it to the scales, please post back to this thread. I was surprised how heavy mine turned out to be, so I'd be curious to hear your results especially since you have a 70s center bath like mine.
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