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Old 08-29-2009, 05:20 PM   #15
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The 80% rule (sometimes it's stated as the 85% rule) has been questioned as to whether it's objective or not. http://www.airforums.com/forums/f238...rom-53739.html

I guess it comes down to whether you trust the manufacturer of your TV. My experience is that Toyota delivers on most everything and more and thus, I tend to trust their ratings. The only difference I can see on my 1/2 ton Tundra compared with a 3/4 ton is it has one less leaf spring. Even so, I like to leave some margin to lessen wear and tear.

Different personalities will approach this differently. More independently derived info on a set standard will be helpful.

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Old 08-30-2009, 09:49 AM   #16
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From what I see in this thread, it interests me how the "80% rule" appears to have been elevated from a rule of thumb or starting point for basic guidance into an absolute dictum.

A lot of vague generalizations often suggested to help guide decisions (but not make them for you) seem to get turned into inviolable rules and, as a result, a lot of folks make bad decisions for their own needs and circumstances.

But there does seem to be a yearning for edicts from on high so one does not have to go to the trouble of making one's own decisions nor take responsibility for them. All one has to do is to suffer the results and that, for some reason, seems to be preferred.
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Old 08-30-2009, 11:32 AM   #17
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It seems to me the SAE fails to recognize that each 150 pound passenger in the tow vehicle reduces the tongue weight carrying capacity by that much, which MAY reduce total trailer weight capacity by as much as 1500 pounds (with 10% tongue weight). That depends on whether the GVWR and GAWR are limiting factors.
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Old 08-30-2009, 12:52 PM   #18
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RoadKingMoe, Yes, you are alluding to an area, in which SAE, and many others fear to tread.
A very typical TV of today, is a 1/2 ton, crew-cab, pick-up, of whatever make, with a typical payload, of ~1700 lbs.
Lets look at a set-up, just for kicks;
1, Mom & Dad, 400lbs, (3/4 of population is overweight)
2, Kids, & Dog 200lbs.
3, Camper shell, rack, and canoe, 300lbs.
4, Generator, and fuel, 200lbs.
5, BBQ, bags of fuel, 50lbs.
6 Tools, bicycle(s), miss. stuff, 150 lbs.
7, Full tank of gas, 25 something gal.,,~175lbs.
8, Personel items in vehicle, ~25lbs.
9, Hitch, and trappings, 100lbs.

Well, we got ~ 1,500 lbs. now, so we have, at very max, about 200 lbs. left for tongue weight.
At 10>12 % tongue weight, looks like we can tow about a 1,500, to 2,000 lb. trailer.

Golly Gee, what happened to the 7>8>9K tow rating.
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Old 10-26-2009, 05:53 PM   #19
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As overdue as standards may be (and they are), we are not the only country towing trailers. Others may have reasonable standards to examine and perhaps adopt (such as trailer having a genuine parking brake as in New Zealand).

That said, there is no better way to start off than to scale the new or the "new" TV ASAP after purchase with only owner and full fuel onboard for a true minimum weight. I've rarely seen either a pickup or a small sedan that wasn't 450-lbs over the published shipping weight. Or more.

We know that the only way to verify proper hitch rigging is with a certified scale. However stupid or ignorant some wish to keep Americans, this type of procedure needs to be emphasized by at least RV manufacturer associations. Or, it should be implemented into law that the dealer certify the RV weight at sale (empty tanks, etc).

A check sheet with liquid weights ought to be provided; a worksheet as part of the legal paperwork that shows how to determine aspects of towing where RV weight is a factor (pin or tongue weight; axle & tire ratings, etc) as well as safety chain certification tags, etc.

Past that point is the reasonable responsibility of the new owner, but liability is a two way street, IMO. This would, I believe, be better than changing drivers licensing requirements. You can bet that someday, someone (some group) will want to pressure RV's off the road -- they'll the horsepower to do it -- and will do it with scary accident info.
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Old 10-26-2009, 10:46 PM   #20
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I see your logic and some of the numbers are high for our situation, but I submit the following after the 40k mile oil change on our 08 f150. It has lugged our 28 nationwide over 22k miles and heading west again, currently in Colorado. I asked the Ford dealer today to look for any issues in the drive train or suspension that may need attention. Nothing, all green check marks. It would seem with your analysis the damn thing should be ready for retirement. I think this tow rating thing is very subjective, and a real issue is frontal surface area. I swear I have been passing more diesel than ever with fivers that have a virtual sail for resistance. I mean some look comical and should be pulled behind a semi tractor. The beauty of the Airstream design is its elegant simplicity of less is more. I respect it more than ever.









area, in which SAE, and many others fear to tread.
A very typical TV of today, is a 1/2 ton, crew-cab, pick-up, of whatever make, with a typical payload, of ~1700 lbs.
Lets look at a set-up, just for kicks;
1, Mom & Dad, 400lbs, (3/4 of population is overweight)
2, Kids, & Dog 200lbs.
3, Camper shell, rack, and canoe, 300lbs.
4, Generator, and fuel, 200lbs.
5, BBQ, bags of fuel, 50lbs.
6 Tools, bicycle(s), miss. stuff, 150 lbs.
7, Full tank of gas, 25 something gal.,,~175lbs.
8, Personel items in vehicle, ~25lbs.
9, Hitch, and trappings, 100lbs.

Well, we got ~ 1,500 lbs. now, so we have, at very max, about 200 lbs. left for tongue weight.
At 10>12 % tongue weight, looks like we can tow about a 1,500, to 2,000 lb. trailer.

Golly Gee, what happened to the 7>8>9K tow rating.[/QUOTE]
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Old 10-26-2009, 11:10 PM   #21
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All I would ask - or reasonably expect - is that there is some "standard" reference to what is "included" in the tow ratings...

I know from personal experience that it is often difficult to determine what the manufacturer included when establishing the "towing capacity". If they would just say that they started with a "base" truck and a 150 pound driver with no passengers and a 1/2 tank of fuel, we would all know the starting point. In my experience though, that information is typically buried in a document that is hard to find. Checking the web site or the dealer is often an effort in futility.
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Old 10-26-2009, 11:42 PM   #22
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I agree the info is hard to find. It can be scattered through the owner's manual, a website and some brochures at the dealer. Toyota includes a full gas tank and coolant before it figures payload, other companies may not. That can make a difference of more 200 lbs.

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Old 05-31-2010, 06:40 AM   #23
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Revived:

Came across this article about Chev no longer needing WDH on some models. Part of a GM press release.

Towing capacity

That leads to the biggest news of all: The 2011 Chevy Silverado HD doesn’t require a weight-distributing hitch to up to its maximum 16,000-pound trailering limit on the Dually and 13,000 pounds on single-rear-wheel models.

The weight-carrying and weight-distribution limits are the same. The maximum towing capacity (13,000 to 16,000 pounds depending on model) is the result of using the protocols for the upcoming SAE J2807 testing standards, which will be put into play in 2013. This puts GM trucks two years or more ahead of the new towing certification program.

“You can tow up to 16,000 pounds [3500 model] in the conventional weight-carrying mode, which is towing on the ball and shank,” says Jim Mikulec, lead development engineer for GM HD trucks said during a recent press briefing.
“In short, the consumer no longer needs to use a weight-distribution hitch.”

In the world of towing, this is huge news.

Eliminate the hitch

In years past, to have your pickup properly-equipped as stated in the owner’s manual, all GM H-D pickups required the use of a weight-distributing hitch when trailering more than 7,500 pounds, while the majority of other manufacturer’s pickups required a W-D for trailered loads weighing more than 5,000 pounds.

Through the chassis, brakes and drivetrain changes GM engineers have found a way to eliminate the need for an aftermarket weight-distributing hitch. The new pickup’s door tag will probably show both the “weight-carrying” (trailer hitched straight to the ball/shank) and “weight-distributing” ratings being one and the same. (See SAE J2807 for details.)

Although GM marketing has overlooked this point, it’s probably the biggest news of all as GM becomes the first manufacturer to build a pickup and hitch package capable of towing this much weight without requiring the use of a weight-distributing hitch assembly.

This should great news to those who tow travel trailers and heavy equipment trailers on the factory hitch because this eliminates 1) having to deal with the set-up and expense of a W-D hitch, and 2) removes any confusion as to having the vehicle properly equipped when it comes to towing limits and related vehicle operator liability issues facing older pickups.


2011 CHEVY HD PICKUPS | Pro Pickup



SAE J2807 Tow Rating
Tow Ratings Finally Pass the Sniff Test - The Society of Automotive Engineers (SAE) - Automobile Magazine



Trailer Body Builder Magazine
LETTER TO EDITOR

The statement “too much tongue weight can force the truck down in the back, causing the front wheels to lift to the point where steering response and braking can be severely decreased” is not the real issue with heavy tongue weights. The real problem is that the tow vehicle's yaw stability, as measured by “understeer gradient”, is severely decreased. This increases the propensity of the tow vehicle to jackknife in turning maneuvers. Specifically, recent full scale testing conducted by the SAE Tow Vehicle Trailer Rating Committee (and now published in SAE J2807), determined that the use of weight distributing hitch torque should be minimized. In fact they recommend that the Front Axle Load Restoration (FALR) not exceed 100% (100% means that the front axle weight is brought back, via weight distribution, to a weight equal to its “no trailer” condition).

(Article referenced in letter)
Tips for understanding the dynamics of properly specifying a truck and trailer combination


(From a post on rv.net)

"Combination Handling Performance Requirement

This is the first time we've seen trailer handling as a requirement for creating a towing standard. The SAE test measures tow vehicle understeer and trailer sway response using specific calculations found in SAE J266. Information that goes into the calculations includes

- effective tongue length (ETL), which is the distance from the center of the trailer coupler ball to the center of the trailer wheels.

Another factor is the amount and positioning of the cargo on the trailer. In one test, weight is securely added to the trailer to bring the combination up to its intended gross combined weight rating (GCWR) and trailer tongue weight.

Then under acceleration they measure G forces at 0, 50, and 100 percent front axle load restoration (FALR).

FALR is the percent change in front axle load due to weight distributing hitch application divided by change in front axle load due to addition of trailer tongue weight. This test is pass or fail and is only used in testing bumper towed trailers."



Anyone come across other, more informative articles/links/posts about the changes made by GM to chassis, brakes & drivetrain?

.
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Old 06-01-2010, 09:07 AM   #24
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interesting that decreasing steering response is not the real issue while decreasing steering response aka 'understeer gradient' is. It seems to me that that is playing games with words.

It is also interesting for someone having not seen something (handling) in a standard that hasn't existed before. I need someone to explain to me why not seeing something that hasn't existed is remarkable. I must be missing something.

As for GM, the key point is what they are doing to the vehicle in order to be able to handle thousand pound bumper weights without its shifting the load on the axles sufficiently as to impact controllability.

Now I have to go look (again) at the definitions of oversteer vs understeer as I get the names and the phenomena mixed up. Towing trailers tends to cause turning more than you steer, which I thought was oversteer. (answers at yahoo)

With the links and the questions it looks like I've got some researching to do and questions to find answers to! good stuff.
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Old 06-01-2010, 09:40 AM   #25
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This reminds me again why I quickly learned in college that engineering was not for me. The fools at that university actually thought I was qualified for that major.

But, despite the fact I don't understand most of what I'm reading—I can't remember the difference between over- and understeer either—I don't get how GM can make the truck stay level when hitched up. The GM PR doesn't say anything to me except "look what we did" but doesn't explain how. Sounds like advertising fluff to me.

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Old 06-01-2010, 10:18 AM   #26
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It's hard to sort out towing claims from the big three into the relevant categories:

Category 1. Uprating a previously derated specification for marketing reasons without running any tests, performing any analysis, or changing the product.
Category 2. Changing the safety margin or testing methodology so that a higher specification can be claimed.
Category 3. Running enough new tests and performing more thorough analysis to figure out that the product will actually perform better than the previous rated specification.
Category 4. Actually changing the product to improve its performance.

I think this is a Category 2, but it's hard to tell for sure.
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Old 06-01-2010, 12:22 PM   #27
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SAE has taken a step forward by making it an equal playing field but they have really only scratched the surface when it comes to putting a combination together and having it run reliably and safely.

We still have the many other factors that influence.....

Aerodynamic factor
Amount of towing hours
Where will the towing take place ?
Handling characteristics of the TV and Trailer
Quality of hitch and connection hardware
Set up and adjustments
Age and mechanical condition of vehicle and trailer
Etc, etc, etc
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Old 06-01-2010, 12:51 PM   #28
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+1

The V-5 standard, when adopted, helped wring some of the BS out of the hitch industry. At that time, there weren't any OEM hitches to speak of.

I don't think that trailer hitches subject to stress loads from a WD hitch have an easier time handling the tongue load, because it's the inertial load when the rear wheels of the TV hit a bump that stresses the hitch the most. The V-5 standard relaxes the requirements, and it shouldn't. I haven't read the SAE standard but would guess that it imposes the same requirements in both scenarios, hence the change.
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