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Old 09-03-2013, 07:25 PM   #15
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Originally Posted by andreasduess View Post

We pull a 34' 1984 International with a Honda Odyssey, fitted with a custom hitch and a transmission cooler. It has a comparable payload to the F150 (around 1400lbs) and the six cylinder overhead cam engine delivers ample power for our needs, 260hp.

Ontario is mostly rolling hills. On the highway we settle at 2000rpm at 65mph, at a fuel consumption that's rarely above 15mpg, slightly more if the wind is consistently against us. I am constantly amazed how often the green ECO light comes on, telling me the engine is now running on four cylinders.

All this not to convince you to buy a minivan, but to tell you the F150 should do just fine

Also, keep in mind that trailer length does not equate trailer weight. Our 34' weighs in at 6250lbs empty, with a tongue weight of just over 600lbs. That's considerably lighter than many shorter trailers manage.
My 2004 Odyessy has a 3500# tow limit and an 8100# GCWR. How are you towing that 34 footer with a minivan?
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Old 09-03-2013, 08:40 PM   #16
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My 2004 Odyessy has a 3500# tow limit and an 8100# GCWR. How are you towing that 34 footer with a minivan?
By concentrating on what I consider to be the important numbers - payload and axle rating. I consider published tow limits an arbitrary number at best, given that the car manufacturer has zero control over the type of hitch, the kind of trailer, sway control, weight distribution, loading of the trailer etc. A 2000lbs badly connected box trailer can cause huge problems where a 7000lbs properly connected Airstream can tow straight and true.

My 34' is a 1984 International, with a very low tongue weight of 625lbs empty, about 750lbs full. The 2008 Odyssey has a total payload capacity of 1400 lbs.

With weight distribution, about 250lbs of the tongue weight is being carried by the trailer (three axles help here), leaving the Honda to carry the reamining weight - around 500lbs.

This leaves me 900lbs for gas, passengers etc, i.e. ample.

The Honda is equipped with a six cylinder overhead cam engine that develops 260hp, which is more than enough to tow my trailer. At my typical towing speed of 60mph, the engine settles at 2000rmp and delivers 15mpg.

To make sure the transmission doesn't overheat an aftermarket transmission cooler has been fitted. The hitch is a custom setup with an additional anchor point transferring weight forward. A Hensley Hitch delivers an incredibly stable towing experience and a decent brake controller stops the rig faster than the car can stop without the trailer attached - again six wheels with large brakes help here.
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Old 09-04-2013, 07:42 AM   #17
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I consider published tow limits an arbitrary number at best, given that the car manufacturer has zero control over the type of hitch, the kind of trailer, sway control, weight distribution, loading of the trailer etc.
For safety, published tow limits should be considered UPPER limits, as in, do not exceed. Installed equipment may lower those numbers, but not raise them, unless you also make suspension and/or drivertrain modifications to the tow vehicle.
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Old 09-04-2013, 07:13 PM   #18
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For safety, published tow limits should be considered UPPER limits, as in, do not exceed. Installed equipment may lower those numbers, but not raise them, unless you also make suspension and/or drivertrain modifications to the tow vehicle.
I respectfully disagree.

Given that I am not exceeding the total allowable payload of the vehicle, there is no need to modify the suspension - the Honda sits straight and level with plenty suspension travel left. Hitching up my Airstream is the weight equivalent of three adult passengers - the Odyssey is designed to carry eight, plus gas and luggage.

The drivetrain is not under any more stress than driving in the mountains would put it under. To make sure the transmission doesn't overheat, I've added a transmission cooler. Under normal acceleration, the engine rarely revs above 4000rpm. As an overhead cam engine, it is designed to rev far higher without taking any damage. At 60mph the engine settles at 2000rpm, frequently selecting ECO mode, i.e. switching two cylinders off.

It seems to me that published tow limits are more often decided upon by the marketing than the engineering department. Payload and axle ratings, those I take very seriously indeed. Tow ratings, not so much.
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Old 09-05-2013, 02:44 AM   #19
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After converting the truck to a complete level ride air bag suspension (all steel springs removed), the weak link in the suspension are the axle ratings. The factory installed Michelin load E rated tires have a maximum pressure of 80 psi, but when inflated to 60 psi on the front and 70 psi on the rear per the door label (and the tire charts), the tire capacity equals the axle rating.

Having said that, the total of the axle ratings is 11,510 pounds but the GVW is 9,600 pounds. The one ton has an additional rear spring using the same rear axle and has a GVW of 10,100 pounds. Since my rear airbags are rated 10,000 pounds, I have no concern with seeing a higher than 10,000 pound truck weight on the scales. Using the Hensley hitch, I am crowding the front axle limit more than the rear axle limit.

On a recent trip, the CAT scales reported 4,820 pounds on the 5,500 pound rated front axle and 5,300 pounds on the 6,010 pound rated rear axle. The trailer axles were supporting 5,880 pounds for a total rig weight 16,000 pounds.

With these load numbers, the front axle was actually 60 pounds lighter than when empty and the rear axle was carrying 1,860 pounds more than when empty.

When I return home in two weeks, I will have two sets of four individual wheel scales awaiting to ascertain the existing individual tire loads. I am thinking there will be a left right difference in the truck tire numbers when unhitched and no payload in the back because of the larger under bed fuel tank, but the trailer may be closer to equal side to side.

By adjusting the location of the two generators, gasoline and water tanks and spare propane tanks in the pickup bed, I should be able to have the loaded truck tire loads closer to being equal side to side.

The trailer may be about 1/4" lower in the front when hitched and that may slightly impact the numbers between the front and rear axles.

After the new trailer comes, I will load the rig to camping weight and then tweak the rear air bag level to bring the trailer closer to level.
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Old 09-05-2013, 06:36 AM   #20
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Quote:
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For safety, published tow limits should be considered UPPER limits, as in, do not exceed. Installed equipment may lower those numbers, but not raise them, unless you also make suspension and/or drivertrain modifications to the tow vehicle.
^
X2

You can ignore the Factory spec's, but IMO the above statement stands.
Substantial modifications can be made that will improve those numbers but for most it makes more sense to start with a better platform.

Payload, should be part of the TV, trailer combined weight limitations.
It's human nature to pick & choose, but in my experience prudence is the better course of action.

Switz has done it right....paying careful attention to ratings that cannot be changed without a complete TV re-build, while at the same time substantially improving the ride and handling of his TV.

Bob
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Old 09-05-2013, 06:42 AM   #21
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Quote:
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For safety, published tow limits should be considered UPPER limits, as in, do not exceed. Installed equipment may lower those numbers, but not raise them, unless you also make suspension and/or drivertrain modifications to the tow vehicle.
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Originally Posted by andreasduess View Post
I respectfully disagree.

It seems to me that published tow limits are more often decided upon by the marketing than the engineering department. Payload and axle ratings, those I take very seriously indeed. Tow ratings, not so much.
Tow ratings are much more likely to be OVER-estimated than UNDER-estimated by marketing, so treating the published limit as an UPPER limit is still prudent, even if you disagree with the numbers. I would think twice, and twice again, before going over a possibly over-estimated limit!
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Old 09-05-2013, 12:44 PM   #22
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Tow ratings are much more likely to be OVER-estimated than UNDER-estimated by marketing, so treating the published limit as an UPPER limit is still prudent, even if you disagree with the numbers. I would think twice, and twice again, before going over a possibly over-estimated limit!
From my own experience in the field, I am certain that tow ratings are almost always radically underestimated when pertaining to a car that is not specifically sold as a tow vehicle.

As I've said before, a 2000lbs badly set up box trailer can cause far greater problems than a 9000lbs properly setup Airstream. Tow rating cannot account for the difference in this, as a result manufacturers err on the side of extreme caution. Like most everything else, this is a risk/reward calculation for them. It's far easier to slap a low tow rating on a vehicle and call it day than to specify a certain setup - sway control, weight distribution, load distribution, brake controller, transmission cooler - that would push this number to a far higher level.

Also keep in mind that my setup isn't something that just happened - it was created by a firm with over 40 years experience in setting up custom towing combinations and an impeccable track record, a firm that consults with both Airstream and the Institute of Automotive Engineers. I trust their expertise over a number I know to be arbitrary.

Again, none of the important numbers, payload and axle rating, are breached. Few people would even raise an eyebrow would I tow with a Ford F150, which has almost identical specs to the Honda - with the Honda being the more stable platform, with a lower centre of gravity and a far more sophisticated suspension setup.

And finally, take a look at this picture. That's the same model Airstream I own, towed by a car with not even half the capabilities of mine.

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Old 09-06-2013, 06:16 AM   #23
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Will the real axle rating please identify yourself

As an educational exercise, go to the Airstream web site and download a few years worth of "Parts Manuals" and check out the trailer axle section. In many cases, one will find a common part number axle is shared across several models and lengths of trailers with different ratings beside the door of the units to which they are attached.

As one example, the three current Classics all have the same 5,000 pound rated axle. The 27FB has a GVW of 9,000 pounds while the two longer units at 31' have a 10,000 pound GVW.

From the 2013 International Parts Manual, Part number 410980-02 is a 3,800 pound rated axle for the 2013 International model trailers. That axle is used on the 28', 27', 25', and 25 & 27 FB Eddie Bauer models. The door label on my 2013 25FB International Serenity says the axle is rated 3,600 pounds. So what is the correct axle rating, the Airstream number on the door or the parts manual that seemingly reflects the axle manufacturer's rating? While the 25' models have a 7,300 pound GVW, the 27FB models have a 7,600 GVW except for the Eddie Bauer model with a 7,800 pound GVW.

The US model 19 gets a 4,300 pound axle (GVW is 4,500 pounds) while the Canadian unit gets a 5,000 pound axle. The 23D and 23FB both get a 3,000 pound axle (GVW is 6,000 pounds) while the 30' model now gets a 4,500 pound axle with a 8,800 pound GVW.

The factory puts the same GYM ST 225/75R15D tire on all units 19' and 25' and longer so the tire is not the limiting factor. The same shock absorber assembly is used on all sizes of the International units.

There is a 27FB International Serenity parked adjacent to our 25FB International Serenity and they were made the same month and are within 35 units of their serial numbers. The 25FB had a user payload weight of 1,635 pounds on the door sticker while the 27FB had a user payload weight of 1,686 pounds on it's door sticker. The GVW of the 25FB is 7,300 pounds while the 27FB has a 7,600 pound GVW. The 2013 Airstream literature claimed a 1,688 pound user payload for the 25FB, a 1,776 pound payload for the 27FB and a 1,825 pound payload for the 27FB Eddie Bauer. The adjacent 27FB could have had the microwave installed.


So all this information does add weight to the thought that some important numbers are being pulled out of thin air for marketing purposes.
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Old 09-06-2013, 06:25 AM   #24
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Quote:
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As one example, the three current Classics all have the same 5,000 pound rated axle. The 27FB has a GVW of 9,000 pounds while the two longer units at 31' have a 10,000 pound GVW.

From the 2013 International Parts Manual, Part number 410980-02 is a 3,800 pound rated axle for the 2013 International model trailers. That axle is used on the 28', 27', 25', and 25 & 27 FB Eddie Bauer models. The door label on my 2013 25FB International Serenity says the axle is rated 3,600 pounds. So what is the correct axle rating, the Airstream number on the door or the parts manual that seemingly reflects the axle manufacturer's rating? While the 25' models have a 7,300 pound GVW, the 27FB models have a 7,600 GVW except for the Eddie Bauer model with a 7,800 pound GVW.

The US model 19 gets a 4,300 pound axle (GVW is 4,500 pounds) while the Canadian unit gets a 5,000 pound axle. The 23D and 23FB both get a 3,000 pound axle (GVW is 6,000 pounds) while the 30' model now gets a 4,500 pound axle with a 8,800 pound GVW.

The factory puts the same GYM ST 225/75R15D tire on all units 19' and 25' and longer so the tire is not the limiting factor. The same shock absorber assembly is used on all sizes of the International units.

There is a 27FB International Serenity parked adjacent to our 25FB International Serenity and they were made the same month and are within 35 units of their serial numbers. The 25FB had a user payload weight of 1,635 pounds on the door sticker while the 27FB had a user payload weight of 1,686 pounds on it's door sticker. The GVW of the 25FB is 7,300 pounds while the 27FB has a 7,600 pound GVW. The 2013 Airstream literature claimed a 1,688 pound user payload for the 25FB, a 1,776 pound payload for the 27FB and a 1,825 pound payload for the 27FB Eddie Bauer. The adjacent 27FB could have had the microwave installed.
While slinging numbers around, don't forget that the trailer load is supported by the axles AND the trailer tongue. So the load supported by each axle isn't just GVW divided by the number of axles, it's somewhat less.
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Old 09-06-2013, 07:06 AM   #25
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Don't get me going on CCC.....

676lbs....really?

7300lbs. on two 3500lb axles leaves very little wiggle room

At least AS has started matching axles to trailer weights.

Bob
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