Owners Manual Warning - Stiff T.V. Springs

[slowmover]

Yes, jmtandem, I read that as meaning (deduction) that my 3/4T was limited to "about" a 10,000-lb trailer due to TW. The factory tow package hitch receiver isn't very impressive. But even with an aftermarket "beefier" hitch receiver, your point is well taken that a work related function is not at all clear or forthright in outlining the steps necessary to towing properly (however that should be defined). The lack of definitions anywhere we turn in re WDH's is aggravating as can be.

If the argument is that there are too many possible combinations used in too many possible ways (road, lack of road, etc, ad infinitum), then how about quoting relevant sections of SAE papers so we can at least look over the shoulder of those who test these things for their "ratings".

(I believe it was "markdoane" who provided this quote I copied unattributed):

*W. Korn, "Travel Trailer Design and Construction - How It Relates to Towability." SAE SP-259, January 1965

*R. Thomas Bundorf, "Directional Control Dynamics of Automobile-Travel Trailer Combinations" SAE Paper 670099, Jan. 1967

The Bundorf paper uses tire cornering stiffness and sideslip angles (for both the tow vehicle and the trailer) to calculate the yaw forces acting on the combination. These are used to describe the motion of the trailer and tow vehicle as a rotational inertia-spring-damper system, which leads to the frequency and damping equations.

From there he calculates the yaw velocity, sideslip angle, lateral acceleration, and towing angle responses.

What is really neat is that he can then change the tongue weight, TV rear overhang, tire stiffness, and 'centering force' (sway control), and determine the stability following a pertubation such as a passing truck.

And I am now waaay off topic, but it is the sort of information (endnotes, bibliography) that might put some usefulness into Owners Manual discussions. After all, testing has a beginning and an endpoint, and must work from particular definitions.

Or, in this quote off of rv.net:

"

I worked at Ford's Arizona Proving Ground in Yucca, Az till they closed it last year. (2007 or 8). It was a truck/desert/durability-proving ground. When we did tow testing -- which was 10,000 miles -- we loaded a trailer to maximum GVW for that vehicle. Anything from a F450 to an Escape. The tongue weight was set at 10-12%. We had a stop and go course, and a high-speed 5-mile oval that we did on-site trailer towing upon, but about 80-90% of the 10K mile towing was on public highways.

On the public roads we drove to Bullhead City on Highway 68. BHC is at the bottom of a 12-mile-long, 6% grade. The driver left the proving grounds at the start of the 8-hour shift and drove the 60 miles to BHC, and for the next 5 hours he drove up & down the 12-mile 6% grade. We did that 24/7, 365-days per year. In the summer 125-degrees Farenheit is a routine temp along the Colorado River in this area. We did these tests with all our trucks, and all the competitor's trucks. We always tested at 100% GVW. Never 80%."

. . is about the only "argument" (entirely anecdotal, thus nearly worthless) about respecting GVWR, etc, and the falsity of the "80% rule".

Same for Airstream and warning against TV rear springs that are "too stiff" without (I assume) providing any guidance as to what that means, or how to calculate said problem. That a WDH sets up/affects a set/series of relationships is understandable and not open to bald pronouncements makes for difficulty, I'll grant. But the lack of basic perspective as given, undefined, by trailer and tow vehicle manufacturers is not acceptable per your example, and the original post of this thread.

Since the whole thing is about money (who is liable for repairs), it also seems moot. Another dead end.

[jmtandem]

Red,

In no way was I arguing with you. In fact my current trailer only weighs 8000 pounds. I got the truck to haul a 4000 pound cabover camper and still needed air bags and overload spring bumpers. If the truck's towing capacity is limited to the hitch, then it can tow more with a Class V hitch or a Fifth Wheel hitch. Their own analysis proves that out as they are rated higher with a fifth wheel hitch.

The more time I spend (many years since 1985) with cabover campers and lots of pleasant hours on the forums, I have learned that many, if not most, with cabovers are over some rating, usually the GVWR. I was not as I was more cautious about things like that. However, those that are ususally state their case as looking for the weakest link, tires, rims, axles, transmissions, brakes, engines, springs, etc. Often they respond to that weak link with aftermarket improved components and therefor are OK. Not being a lawyer, I think it would be arguable either way that if a deliberate progressive attempt to make the truck haul better was carefully undertaken, the truck could haul more. Look at the F 450, or the Dodge 4500 etc. and see what is really different compared to a 350 or 3500. Or a 2500 like you have compared to a 3500. What really makes a one ton that is not found in a three quarter ton? Same engine, transmission, tires, wheels, maybe a spring or two in the spring pack, maybe bigger brakes, etc. So, if you upgrade a three quarter ton to one ton components it should tow or haul like a one ton? I don't really know. But, do think a good lawyer could argue either way.

I am not aware of any accidents where anybody actually got the trailer weighed in relation to the truck. That could shed some light on this issue as it relates to the video you shared. I spend lots of time in the toyhauler section of the rv/net forums as they are as heavy as 18,000 pounds often towed by one tons and could find not one example of an accident where somebody was cited for being overweight. Maybe there are cases but I have not run into them. However, that being said, there is no safe way to tow more than should be towed and for the sake of family and others on the roads it should not be done. If Dodge really cared about how we tow, more than three of 366 pages in the manual would be devoted to the subject and it would not read like the same narrative covers minivans through medium duty trucks. And, of course, the max towing ratings are dependent on class of hitch as much or more than the rest of the truck. I apperciate what you said, always use a WD (now Equalizer 1200/1200) hitch and sway. I don't like to take chances. However, for my truck with the very heavy diesel engine all that I really need is sway as 1000 pounds on the hitch is only about 25% of the payloads capacity of the truck. Since my hitch cannot be used without WD to also get sway, I just go light on the bars to have sufficient tension for sway.

Good thread and good posts!

[jmtandem]

Road Ruler and W7,

I had no idea Equalizer has been in business that long. That must be a testimony to a quality product. Now, they do need to update and modify the hitch to allow the hitch head to take various spring bars without needing a separate hitch head for each spring bar rating. What if you have different trailers with a need for different spring bars? Also, the short shank ball and the close space within the shank nut area should be modified. Is it really necessary to need a special ball and a special thin wall socket to tighten the nut? I am glad they modified the L brackets, addressing a common issue. Now fix the head to use interchangable spring bars.

I have only been RVing since about 1985, prior was tent camping out of a vehicle or from a motorcycle. Since 1985 and three cabover campers later I am now a travel trailer owner and learning all I can about towing.

I did watch the movie 'Long Long Trailer' and was surprised to see the tow dolly for tongue support. I never thought about that working and wonder why it is largely not used today. Pretty impressive trailer for a car with about 125 horse power especially the scenes at the Whitney Portal access road, a short distance south of where I live. I have been on that road, it is steep, narrow and with tight curves.

[Road Ruler]

Originally Posted by REDNAX

Or, in this quote off of rv.net:

"

I worked at Ford's Arizona Proving Ground in Yucca, Az till they closed it last year. (2007 or 8). It was a truck/desert/durability-proving ground. When we did tow testing -- which was 10,000 miles -- we loaded a trailer to maximum GVW for that vehicle. Anything from a F450 to an Escape. The tongue weight was set at 10-12%. We had a stop and go course, and a high-speed 5-mile oval that we did on-site trailer towing upon, but about 80-90% of the 10K mile towing was on public highways.

On the public roads we drove to Bullhead City on Highway 68. BHC is at the bottom of a 12-mile-long, 6% grade. The driver left the proving grounds at the start of the 8-hour shift and drove the 60 miles to BHC, and for the next 5 hours he drove up & down the 12-mile 6% grade. We did that 24/7, 365-days per year. In the summer 125-degrees Farenheit is a routine temp along the Colorado River in this area. We did these tests with all our trucks, and all the competitor's trucks. We always tested at 100% GVW. Never 80%."

One really wonders how much truth there is to the above account. If Ford does all this testing wouldn't they have realized how bad the Ford Explorers (pre 2003) were for towing and adjusted the trailer pkg equipment on them to make them acceptable.

I saw an Explorer here abouts that had the Can Am mods. LT tires, Monroe gas shocks, reinforced factory receiver etc. The owner commented that the mods made a night and day difference when towing. Why was Ford so lame that they couldn't figure this stuff out??

[pmclemore]

I'd guess there is a difference between just testing and using the results of testing to improve the product.

Good observation. Pat

[Ganaraska]

To answer the original question. Here is what they are driving at.

You DO NOT need super heavy duty springs or heavy duty spring bars on your hitch. In fact, too stiff springs and too stiff spring bars are worse than too light.

There have been MANY cases of Airstream trailers damaged, the fronts bent, and shaken to pieces by too stiff springs, too stiff spring bars, and too heavy duty tow vehicles.

There have been some very long, in depth, informative threads on this subject. But the consensus is most car dealers, trailer dealers and owners tend to go too heavy duty thinking if some is good, more is better so too much should be just right. This is not true.

So go easy and you will be fine.

[Airstreamer67]

REDNAX, at your suggestion, I just re-read the owner's manual for my 3/4 ton truck. The "towing" section comprises 33 pages of the 420-page manual, or about 7.9% of the total.

My manual goes through all the weight limitations and provides a lot of good towing advice including load balancing, etc.

As I noted in my answer above, my truck's cast-iron diesel engine puts a lot of weight on the front axle, so much so that I must be careful not to overload it. In fact, my owner's manual has a warning:

"NOTE: Diesel-equipped vehicles not recommended for snow plowing."

This is put in there because the weight of a snow plow can overload the front axle. Taking a bit of weight off the front axle with a load in the rear can do some good for my truck. It rides better with a load than without.

The owner's manual has only one reference to weight-transfer hitches. It reads:

"Load-equalizing hitches on large rigs may transfer weight to each of the vehicle's axles. This weight must be included in capacity calculations when determining if the vehicle is loaded within safe limits."

In reference to your warnings and the attached article's warnings about various legal implications of towing, it appears my owner's manual does not contradict my techniques in any way. Each rig must be judged by its own distinctive characteristics, and too much generalizing may be misleading.

As far as legal liabilities, anyone who tows is already at great risk if your own statement is to be believed regarding the assertion that "trailer towing doubles the risk of loss-of-control accidents." A trial lawyer could make all of us look like reckless fools in court with that assertion if we have an accident while daring to tow a trailer on public roads.

As in all situations, we must all use good common sense when following all the dogma.

Regarding the original poster's topic, my answer is using a heavy-sprung vehicle for its load-carrying characteristics, and softening the ride with an Air Safe hitch that uses Firestone airbags.

The best of both worlds: a truck that can handle the heavy loads I carry, along with a way to isolate the shock with an air-ride-soft cushion to protect my trailer's delicate limbs.

[Ganaraska]

"I did watch the movie 'Long Long Trailer' and was surprised to see the tow dolly for tongue support. I never thought about that working and wonder why it is largely not used today. Pretty impressive trailer for a car with about 125 horse power especially the scenes at the Whitney Portal access road, a short distance south of where I live. I have been on that road, it is steep, narrow and with tight curves."

Do you remember Nicky freaking out because Tacy was burning up the road at 35 MPH? Lol

The tow dolly was a workaround to allow an ordinary car to tow a heavy trailer with high tongue weight. Did you notice how small those wheels are? About 8 inch diameter, like a wheelbarrow wheel.

I don't think those wheels bearings and tires would stand up to today's speeds. Besides we have better hitches. Once the load equalizing hitches came in, we had a better and cheaper way of dealing with the tongue weight problem.

The 125HP Mercury did well, but did you notice they substituted a Lincoln in the mountain driving scenes? You have to look close to catch it.But it's definitely a Lincoln.

I like the movie and watch it regularly.

[jmtandem]

Ganaraska,

Yes, the tow dolly almost looks like more work than benefit. Yes, the cars were substituted for certain scenes. My opinion is that the trailer was towed by a truck to the filming scenes, then hitched to the car. If you are familar with the Whitney Portal access road it becomes pretty apparent that the car was working very hard to pull the trailer up any grade, and probably did not on the Whitney Portal road. This is the road to the beginning of the Mt. Whitney trail from the Lone Pine (east side) and ends at about 8000 feet in a parking lot, store, trailhead, etc. Since many motorcycles today have more than 125 hp box stock, it is pretty amazing what the previous generation towed with back then. It is an interesting movie and you can see in some places the camera was tilted to make the hill appear even steeper than it is, and it is steep.

[hhendrix]

Wow, I thought this would be easy, but now I have a headache. The reference to the owner's manual caused me to take a look at mine. I have a 2001 F350 7.3 Diesel 4WD automatic towing a 2009 Flying Cloud 27FB. The AS has a GVWR of 7600 lbs. and hitch weight of 790 lbs. according to the specs. I was a little surprised when I first hitched the AS to my 1 ton Ford as to how much the rear of the truck dropped and that was without a WD hitch. I've put loads heavier than that in the bed with little or no drop. But I understand the leverage principle involved when the load is further from the rear axle. I bought a Reese type WD hitch because my receiver required one for over 5000 lbs. GVWR or 500 lbs. tongue weight. The bars are rated at 1200 lbs. The arguments here regarding the cargo loads of 3/4 and 1 ton diesel truck seem to ring true to me. But here is what my owner's manual says:

When hooking up a trailer using a load equalizing hitch, always use the following procedure:

1. Park the unloaded vehicle of a level surface. With the ignition on and all doors closed, allow the vehicle to stand for several minutes so that it can level.
2. Measure the height or a reference point on the front and rear bumpers at the center of the vehicle.
3. Attach the trailer to the vehicle and adjust the hitch equalizers so that the front bumper height is within 0-13 mm (0.5 inch) of the reference point. After proper adjustment, the rear bumper should be no higher than in step 3.

I'm guessing that when I first hitch the AS, my rear bumper drop is a least 3" and and the front raised maybe an inch. I have also gone to an local and reputable RV dealer here and reviewed the proper procedure with their hitch specialist. His procedure was basically the same as recommended by Ford. However looking back and at the manual, I'm confused and wondering if there is a typo in the owner's manual regarding: After proper adjustment, the rear bumper should be no higher than in step 3. Should it read Step 2?

Anyone have a newer Ford manual that says differently? Second question: If the WD hitch bars are rated at 1200 lbs or whatever, what effect does the amount of tension you apply with the adjustment to the number of chain links have on the trailer/TV combination?

OK time for lunch. I might have 2 beers today instead of one. Thanks, Hal.

[2airishuman]

Originally Posted by hhendrix

...OK time for lunch. I might have 2 beers today instead of one. Thanks, Hal.

good plan

yeah, it reads like a typo and should be 'step 2'

i'll look in the newer ford book later, but u might wanna read a few posts in THIS thread...

http://www.airforums.com/forums/f464...sis-19236.html

and this one which actually measured the forces...

http://www.airforums.com/forums/f238...tch-53341.html

read them before AND after the beverage lunch...

cheers
2air'