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Old 08-20-2015, 10:28 AM   #61
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Originally Posted by bono View Post
And if you look at the torsional stiffness test that both Ram, GMC and Ford continue to do in the frame of their pickups they are laughable; impressive for a frame vehicle which is structurally deficient in torsional rigidity regardless of what steel you throw at it, but laughable when compared to a unibody."
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Originally Posted by nrgtrakr View Post
I wasn't questioning a unibody towing. The question stands as written. Rephrased - "How come frame construction can tow so much more than unibody?"
Maybe I missed something, all I saw was 31' AS. Look up the weight for a 31' AS and see what you get. I found a 2013 was 7,254# trailer weight, 805# tongue, 10,000# GVWR.
As you probably know, 7,254# is before options (AC, microwave, battery charger for example) and variable weights (tanks and water heater) - at least that's how AS explains it in 75. Add in food and personal belongings and ...
I chose the high weight on purpose to be safe. But maybe the OP only adds 446# to his when using it, maybe his AS actually weighs less.
But again the main point for me was exceeding the vehicle's capacity.
Except for the uninformed, torsional stiffness is NOT what you want when designing a vehicle for heavy loads. Ever notice why semi trucks have huge ladder frames and while under load especially from a stop they twist and buck when accelerating? This is by design.

A uni-body pickup truck trying to carry/haul the loads of a body on frame pickup truck would simply snap spot welds, contort and would be destroyed.

Ford tried a uni-body pickup before and it was a disaster. Shortly after the trucks went on sale, buyers discovered that putting heavy cargo in the unibody trucks could cause the one-piece body to flex with interesting consequences. Stories percolating through the Internet tell of uni-body owners who would load their trucks, only to discover that the sills had distorted enough to jam the doors shut. Yet others tell tales of having a fully laden truck twist badly enough to pop a door open when crossing railroad tracks. Age and corrosion only exacerbated issues as the load-bearing bodies began to perforate and rust.

You just can't pile as much weight on it before it begins to twist the entire car body in odd ways. On a ladder frame, the weight is transmitted to the suspension and the wheels in a much more direct, controlled way. "Flex" isn't necessarily an issue, since only the frame is flexing and the body is decoupled and riding on rubber mounts. The HD versions of Ford and Ram's trucks (F350, etc) actually have C-channel frames instead of fully boxed frames, like the 1/2 tons do, because allowing a little flex in the frame actually helps carrying and towing capability.


Uni-body vehicles are fine when used within their design specs. Once you start talking about towing and loads thousands and thousands of pounds above that, I tend to disagree.
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Old 08-20-2015, 10:51 AM   #62
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The OP wrote he has a 2015 30 foot.
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Old 08-20-2015, 11:03 AM   #63
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I haven't seen many cars towing travel trailers in Mt., although I've been looking at my wife's Venza !!
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Old 08-20-2015, 11:29 AM   #64
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So the printed weight numbers of the door post versus the scales report is the heart of this long conversation. Which numbers are the ones to fudge? I went across the scale in May with the truck and trailer loaded for camping and me and the wife as the people in the truck.

GAWF 5,500 scales 4,700
GAWR 6,010 scales 5,700

GVW 9,600 scales 10,300

GCW 20,000 scales 18,660

So while the GVW was exceeded, the axle and tire with wheel ratings were under the maximum. The maximum combined weight was under the limit and the trailer weight was less than the maximum. This is a truck which is designed to carry loads. Most states DOT officers are only concerned that tire, wheel and axle ratings are not exceeded and the license plate has the correct weight ticket for the load.

The togue weight of the trailer is now reduced to 1,200 pounds in this example, so the trailer typically weighs around 9,300 pounds unhitched loaded for camping.

For us, the truck is properly sized for the job at hand. We have removed a lot of heavy items after this trip that will probably not be carried any more which will reduce the rear axle load some more.

When we saw a used 34' Classic (last one officially built - #25 of 25), I pushed the numbers and my truck could have been easily overloaded with that trailer that had a GVW of 11,500 pounds. Thus we ordered the 31' Classic with a 10,000 pound GVW that was within the towing GCVW restrictions.
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Old 08-20-2015, 11:38 AM   #65
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Originally Posted by jcl View Post
The OP wrote he has a 2015 30 foot.

Okay ...
2013 - 30' AS 7,365# trailer weight, 773# tongue, 10,000# GVWR
Pick nits much?
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Old 08-20-2015, 11:43 AM   #66
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Uni-body vehicles are fine when used within their design specs. Once you start talking about towing and loads thousands and thousands of pounds above that, I tend to disagree.
I don't think the 60s unibody pickup is as relevant. An SUV doesn't have the roof profile of a pickup, it is more of a one box of two box design. A better example would be a Transit or Sprinter. Available up to one ton class ratings. Unibody. Current design. Designed to carry loads. What don't they know?
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Old 08-20-2015, 11:50 AM   #67
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I don't think the 60s unibody pickup is as relevant. An SUV doesn't have the roof profile of a pickup, it is more of a one box of two box design. A better example would be a Transit or Sprinter. Available up to one ton class ratings. Unibody. Current design. Designed to carry loads. What don't they know?

A 1 ton Sprinter has only a 5000 tow rating.

I have never seen a body on frame race car nor a unibody semi. They make different tools for different applications for a reason.
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Old 08-20-2015, 12:31 PM   #68
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A 1 ton Sprinter has only a 5000 tow rating.

I have never seen a body on frame race car nor a unibody semi. They make different tools for different applications for a reason.
Agreed.
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Old 08-20-2015, 12:50 PM   #69
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The good thing is we see more folks like the Tino's Touareg/Airstream combo all the time who have taken their head out of the sand to understand their is more to safe, comfortable and efficient towing than manufacturer's ratings. Knowing these design characteristics can make all of us choose better tow vehicles, hitches, and Airstream components while still remaining within tow ratings. And for those who wish to push the parameters and do it safely.
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Old 08-20-2015, 01:12 PM   #70
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A 1 ton ( "unibody"....note added by me ) Sprinter has only a 5000 tow rating.

I have never seen a body on frame race car nor a unibody semi. They make different tools for different applications for a reason.

Correct. And in the "Sprinter class", if we look at a Nissan NV, it has a 8700 lb tow capacity. ......and...... a ladder frame. No unibody there.
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Old 08-20-2015, 05:02 PM   #71
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. . . I have never seen a body on frame race car nor a unibody semi. They make different tools for different applications for a reason.
But if you took the best characteristics of both, race car unibody and great full independent suspension and the semi's abundance of low rpm diesel torque along with superior barking ability of either, put them together you'd have a Touareg.

Which at least brings us back to the original topic.
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Old 08-20-2015, 05:36 PM   #72
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But if you took the best characteristics of both, race car unibody and great full independent suspension and the semi's abundance of low rpm diesel torque along with superior barking ability of either, put them together you'd have a Touareg.

Which at least brings us back to the original topic.
....and like a LOT of compromises, it would do neither task well !

That's like saying all I need in my toolbox of hammers is a 16 ounce ball-peen.... I can use it to drive either tacks, or railroad spikes......
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Old 08-20-2015, 06:19 PM   #73
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Okay ...
2013 - 30' AS 7,365# trailer weight, 773# tongue, 10,000# GVWR
Pick nits much?
You are getting closer now that you are looking at 30 foot models.

Now look at the Signature, not the Classic. The weights were in post #73.
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Old 08-20-2015, 06:40 PM   #74
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I have never seen a body on frame race car nor a unibody semi. They make different tools for different applications for a reason.
Maybe the SUVs like the VW are for those who want something that handles more like a race car and less like a semi, while also being able to tow 7700 lbs or so when required.
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Old 08-20-2015, 07:55 PM   #75
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Now look at the Signature, not the Classic. The weights were in post #73.

Sure, I'll play along, but only one weight listed in your post and it doesn't match ...
AS says a 30' Signature weighs 6,382# without options or variables, 880# tongue, 8,800# GVWR.
I wouldn't do it. I used to get paid for doing crazy stuff, I'm retired now.
BTW, doing the numbers on our 75 Overlander 27', minimum options and medium variables added about 1,000#.
So this 30' with a GVWR of 8,800# and a 7,700# TV - No thanks!
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Old 08-20-2015, 07:55 PM   #76
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Except for the uninformed, torsional stiffness is NOT what you want when designing a vehicle for heavy loads. Ever notice why semi trucks have huge ladder frames and while under load especially from a stop they twist and buck when accelerating? This is by design.
Thank you. And this is why layman are not engineers.

Rigidity, torsional stiffness, strength, and durability are all too often conflated on these forums as singular concepts to justify towing beyond a manufacturers specs.

Fact is, they are at best guessing or justifying why they can tow beyond the manufacturers designed limit without truly understanding the system (because cars are complex systems with compromises to meet particular design requirements) limitations.

Sure you can modify one to suit your use case and I've been known to push boundaries. But some assumptions and justifications on these boards are very flawed, and quite scary to me.
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Old 08-20-2015, 07:57 PM   #77
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VW Touareg diesel and 31 foot Airstream

ditto ...
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Old 08-20-2015, 09:40 PM   #78
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This is exactly the reason why I would never drive a pickup. I like X5 which is just all-purpose car for me. It is capable to tow heavy load, despite whining from truck fans. The ONLY concern I will probably have is the constant harassment on the road from the truck drivers... at least this is what I am hearing from German SUV owners towing larger trailers.

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Maybe the SUVs like the VW are for those who want something that handles more like a race car and less like a semi, while also being able to tow 7700 lbs or so when required.
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Old 08-20-2015, 10:02 PM   #79
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Did I miss where the OP was actually asking anyone for their opinion? Maybe the mods should start a dedicated thread where the truck people can feel free to criticize alternative vehicles so that posts like this one, where a person wants to show off his trailer and TV combo, can do so without it being hijacked by people with nothing better to do than rain on his parade.
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Old 08-20-2015, 10:04 PM   #80
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This is exactly the reason why I would never drive a pickup. I like X5 which is just all-purpose car for me. It is capable to tow heavy load, despite whining from truck fans. The ONLY concern I will probably have is the constant harassment on the road from the truck drivers... at least this is what I am hearing from German SUV owners towing larger trailers.

Well the issue about towing isn’t just about a machines ability to tow a 5 to 9K lb. rolling weight (or just gas mileage), but it’s ability to do so under all conditions, hills n’ dales and in avoidance situations... safely. My understanding is that an X5 and VW Touareg weigh in at about 4700 lbs. GVW. Most of the trailers we’ve been talking about here have weighed anywhere from over 5K lbs to about 9500 lbs.

Isn’t that a bit like the tail wagging the dog?

I’m pretty much of the opinion to follow directions and stick with what the manufacturer says it’s vehicle is capable of and give it a wide margin of error. It isn’t about trucks vs. minivans vs. tonka trucks or cars. It’s about safety.

I’ve never married myself to a vehicle so much so as to have to have it where I have to make all sorts of compromises to justify it. It can either do the job it was built to do according to the manufacturer or it can’t. If not, find something else. I could care less what they do in Japan, Germany, Canada or Timbuktu.
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