Tongue weight & trailer size

[Bruce H]

Pete's four points capture the basics of towing geometry very well. Those basics are all four very important. These things in combination are foundational in determining the stability and safety of the combined vehicle. They are more or less fixed during manufacturing of the individual vehicles. The consumer should consider them when evaluating purchases or "building the rig". Most of us are not able to modify our vehicles after we get them. If we understand towing geometry we can choose vehicles that best confirm to Pete's four points.

There are other factors such as aerodynamics, axle, brake, suspension and hitch design and capacity. Then there is the amount of weight and the way loads are placed on the vehicles.

To expound on the topic of tongue weight I will attempt to paint a picture with words. Let me describe a hypothetical trailer. This trailer has a 20 foot long body and a tongue that extends two feet in front of the body. The axle is placed 60/40 with 60% or 12 feet of the length of the body in front of the axle and 40% or 8 feet of overhang behind the axle. This trailer weighs a total of 5000 pounds. It has the "ideal" weight distribution of 4400 pounds on the axle(s) and 600 pounds or 12% of the weight on the ball of the hitch.

Now let me (as the manufacturer of this hypothetical trailer) add a magic component. That magic component is an extendable and retractable tongue that is extended or retracted by means of turning a crank. The tongue is two feet long at the short position and it can be extended eight feet to make it ten feet long at the long position. To make it even more appealing I am fixing it so the operator can choose any length between the two extremes.

This vehicle has an ideal 12% "tongue weight" of 600 pounds at the two foot position. It will obviously have much less than 12% or 600 pounds of tongue weight at the ten foot position. In fact it is going to have much less than the minimum 10% tongue weight specified by the "experts".

Now let me ask these questions:

1. What would those weight figures be with the tongue extended to the ten foot length?
2. How would the stability and handling characteristics on the highway be affected by extending the tongue to the ten foot length?

[Pete Dumbleton]

Here in the West, the extendable tongue is not hypothetical, it is reality. Gravel trucks tow four-wheel trailers with extended tongues. Some are adjustable, some are not. But they are not load bearing, except to support themselves, they are load-pulling. This differs a bit from typical RV trailer tongues.

The recommended tongue weights recommended by 'experts' apply generally to most RV trailers manufactured in North American and are only a Rule of Thumb. They are a starting place, and that's why one sees a range. My experiences reading a number of RV groups is that an incredible number of trailer owners or would -be trailer owners have no idea about what they are doing. And when they come onto an RV group and start asking questions, they will often get the advice to add a friction sway bar...

I suspect the reason RV manfs don't make adjustable tongues is both structural and marketing (What is the true length of the trailer? Is the customer being 'cheated'? etc.).

Interestingly, the setup with great towing geometry, the 5W or Gooseneck hitches, also have the highest 'tongue' (aka pin) weights (15-25%).

[Anders Laurits]

Bruce H, I also adhere to the longer tongue idea. It just makes sense. We read and read on several forums, while contemplating our move from a class A MOHO to a MFGRV. One day we heard about Oliver Travel trailers while cruising the Casita Club Forums. I was pretty much thinking that it was a Casita clone, until I found the photos of the extensible tongue, aluminum frame with the tanks all at the lowest point, with the weight over the axle. I had never heard of such a thing as an extensible tongue. The more I looked and the more I read, the better I liked it. We have ours extended out full length in this photo, to facilitate the generator, it's saddle and cover.

[CD Smith]

Back in the '60s/'70s there was a WDH that put the entire toungue weight of a trailer on the rear axle. No weight added to TV frame and no weight transferred to the tvs front axle although some weight was transfered to the RV axle. This is the ultimate extensible hitch.

I wonder if one of those is still available?

[Pete Dumbleton]

I like that extended tongue -- Shorten it up for ferry use where they charge by length!

A friend of mine did that with a sailboat trailer so he could get the trailer into deeper water without getting TV wheels/axle wet. I have also seen a permanently extended tongue on a Scamp 13 for the purpose of carrying two bikes.

I suspect that the tongue weight itself is not as important as the fore and aft weight balance with respect to the trailer axle (and the distance of heavy stuf in/on trailer from the axle).

Extended tongue, or shortened TV overhang, also makes for better backing on short trailers.

[Bruce H]

[This is the Fiberglass RV forum. One of the appeals of fiberglass RVs is that they are light weight and handle pretty well unless they are being towed with a very small tow vehicle. Most of the real problems I see are in larger heavier conventional travel trailers. However, these principles apply to all sizes of rigs.

In most cases the features I am using as examples are not available on trailers. By using these examples I hope to increase understanding on the part of forum members who happen to read this. Along the way I may learn some things myself. If we have a better understanding of towing geometry and dynamics we can make better choices in our purchases.

Now I wish to make some assertions about my hypothetical trailer with its extendable tongue (listed in my previous post):
• If all other things remain the same, as length is added to the tongue the trailer will become progressively more stable no matter what tow vehicle it is hitched to.
• This 5000 lb trailer with the tongue fully retracted to the two foot length would require a three quarter or one ton size tow vehicle and that combination would still benefit from anti sway bars and/or an equalizer hitch.
• With the tongue fully extended the trailer could safely be towed with no sway bars or equalizer hitch by a much lighter more economical tow vehicle.
• The longer trailer tongue will make it easier to back the trailer.
• The longer trailer tongue will prevent crunching the body of the trailer with the body of the tow vehicle in a tight turn or jackknife situation.

I admit that my example has somewhat unrealistic extremes for the tongue length. But then my example is hypothetical. This extreme example makes it easier to understand this particular dynamic. The tongue functions as a lever that the tow vehicle uses to control the trailer. The length of that lever is the length from the axle of the trailer to the hitch ball. Part of that lever is composed of the body or frame of the trailer. The longer that lever is the more control the tow vehicle has over the trailer. Most travel trailer tongues extend about 3 ½ feet from the body of the trailer. That is too short. If there were trailers sold with an extendable tongue like I described most operators would probably be running them extended about six feet in front of the body. As they gained experience they would extend the tongue farther. I would personally extend it all the way to ten feet until I got to the campground.

The draw backs to a longer tongue are:
• The trailer may catch more wind and cause the tow vehicle to use more fuel. It depends on the shape of the tow vehicle and how the wind comes off of it. A shorter tongue may in some cases actually worsen the aerodynamics.
• The trailer will track in further when turning sharply. That requires extra awareness and care when turning sharp corners into driveways or in close proximity to other vehicles or gas pumps etc.
• The trailer will require more parking space in the camp ground or driveway.
• It may be classified (at a disadvantage) as a longer vehicle by some bureaucracy that regulates or licenses trailers.

It appears that most travel trailers are designed to try to minimize these disadvantages. That winds up being at the expense of the vehicles stability. It also appears that most designers do not fully understand towing physics or dynamics or geometry issues. They proclaim that stability all starts and ends with the 10% to 15% tongue weight rule. This has been repeated so often that most of the public has that perception. From my perspective I believe the disadvantages of a longer tongue are more easily managed and are preferable to the handling and safety issues of a more unstable trailer with a shorter tongue.

[Pete Dumbleton]

Keep in mind that regardless of how long the tongue or trailer is, it takes X horsepower (and the transmission and cooling) to move Y lbs up a hill.

With an adjustable tongue, esp on a home-made rig, you could claim the length when short with a resonable chance of it being accepted. Also, many licensing authorities go by weight or book value for setting fees.

I believe the standard 10-15% used by RV trailer and hitch manfs is reasonable for standard trailers. A trailer that was much longer (or shorter) in front, compared to rear, would require a different approach than the standard.

Commercial Trailers

What you are talking about is more or less in the photo of a Pony trailer. Around the West Coast, I've seen gravel trailers whose tongues are almost twice as long as those in the photo and the only tongue weight is 1/2 the tongue itself.

Almost the opposite effect can be found further down the page, the Belly Dump, where a significant amount of the load is tongue weight.

Here's an example with a longer tongue.

[Bruce H]

For this post I want to add another magic feature to my hypothetical trailer. This feature ties in with the tongue weight subject and it addresses another problem that seems to be prevalent with RVs. That issue is excessive overhang behind the back axle. Excessive overhang negatively affects stability on the road. The weight of many trailers or motor homes is teter tottered on the back axle which makes them significantly less stable at highway speeds. It makes them more susceptible to cross winds and gusts from passing vehicles. It also makes them less safe when maneuvering in close quarters because in a tight turn the overhang will swing to the outside of the turn and bash into other vehicles, gas pumps, walls, signs, pedestrians, etc. They also tend to drag when crossing dips or entering driveways or on other uneven road surfaces. Many owners try to minimize the dragging problem by installing rollers under the back of the vehicle. If you need to install rollers under the tail of your vehicle then your vehicle has a defective design.

I have an acronym for you:

OHIO – Over Hang Is Obscene

It seems like in the RV industry the designers view added space or overhang behind the back axle as somehow being a free add on. In reality during the design process the axle can be placed anywhere along the frame of the vehicle at no additional cost.

To minimize the negative effects of overhang I am going to add a magic sliding axle to my trailer. The axle can be slid by pulling the pins that secure them, applying the trailer brake only and pulling the vehicle forward or backwards with the tow vehicle. This is how the axles are adjusted on commercial semi trailers. I will set the range of adjustment from the very center of the trailer body to the very rear of the trailer body. The operator gets to choose where to set it. As the axle is moved to the rear the vehicle will become progressively more stable and progressively more weight will be transferred to the tongue. In the previous example I stated that as the tongue is extended, progressively less weight is transferred to the tongue. Thus we can combine these two adjustable features by moving the axle further to the rear and extending the tongue to dramatically improve vehicle stability, reduce overhang and adjust the tongue weight on the hitch to an acceptable level.

Now let me summarize. I realize that sliding axles on a travel trailer are not very practical. A crank out adjustable tongue would be more practical but no manufacturer is currently producing one. (Someone in Texas does have a patent on the concept.)

The features of tongue length and axle placement are infinitely adjustable on the drawing board when a vehicle is being designed.

I will close this post by giving an example of a trailer who's designers appear to have taken relative tongue length and axle placement into consideration. That trailer is the common U-Haul trailer that you rent from the U-Haul company. They are in the business of renting to the public. That means a significant portion of their customers do not know what they are doing. The company has to take steps to minimize problems. Their trailer design is one of those steps. They do have requirements for the customer's tow vehicles and they have instructions on loading the trailer to get some tongue weight. I have pulled U-Haul trailers a total of 4,000 miles in the past two years. The tongue is long enough to keep the body of the trailer from crunching the tow vehicle and it gives good leverage on the trailer. The axles are back just a little more toward the rear than most trailers. If the customer half way distributes the load according to instructions the trailer will trail rock solid with no hint of sway and no need for sway bars or equalizer hitches.

If only all RV trailers were like that.

[Pete Dumbleton]

Boat trailers already have adjustable axles, plus the load (the boat) is adjustable. I did exactly that in the early '70s with a dual axle boat trailer when I encountered a lot of sway. Moved both the boat and axles to the rear to get longer front overhang and shorter rear overhang.

Not sure, but I believe my friend's '70s 25' Avion had fore/aft adjustments between frame and axle package. I know he could adjust it vertically.

A year or so ago, one of the BulgeMoble RV manfs had to drop a design that put a huge storage cabinet on the rear because it was not only inducing sway, it was cracking the frame...

BTW, rear overhang on the tow vehicle is also bad. Trailer rear overhang can be a sway inducer, which is why many of us caution against carrying bikes, generators, storage boxes, etc. on rear. TV rear overhang gives the trailer a leverage advantage on the TV to allow effects of sway (There is ALWAYS sway; the questions are How Much? and What Effect?)

TV wheelbase is sort of an analog of the trailer tongue, with more being better (swaywise) in both cases.

[Sandra L]

Hi,Thanks for all the info. I am trying to learn as much as possible prior to purchase, as I have an'05 Sienna with a low rear end.
(Approximately 8" above the pavement.) Oliver trailers makes theirs with an adjustable tongue. http://www.olivertraveltrailers.com/.
I would be interested in your observations. Thanks.

[d_wildemann]

I've got a Casita Patriot, wet weight of 2000lbs, that I tow with a Sienna. We were towing with a Hyundai Sonata and were at the limits permitted for the Sonata. One thing nobody has mentioned is that you also have to consider the weight of the items in the TV. We carry a generator, some camping equipment such as chairs and luggage. Since the Sienna is good for 3500 lbs, except for gas mileage, we don't have to worry about items carried in the TV.

I also have heard that the wet weight for a 17' Cassita is 3500 lbs.

Don

[CD Smith]

My 1999 17' Casita SD weighed in at 3005 lbs. The surprise to me was the tongue weight of 476 lbs. To compensate for the weight transfer from the front axle to the rear axle and to lower the weight on the automatic leveling system I started using a WDH. Fortunately I don't have a load problem with the stuff I carry around in the Escalade.

[Pete Dumbleton]

You might try searching the group for Sienna as there have been many posts by owners, including stuf about the hitch and low rear clearance.

The GXXX system is kind of a pyramid on a see-saw.

For the tow vehicle, there are front and rear GAxleWRs, which add up to more than the GVehicleWR. This means that while the GVWR is the total restriction, too much unbalance and weight on an axle is also a restriction (Some vehicles account for this in part by a Tongue Weight restriction).

The difference between the Curb Weight of the vehicle (Usually one driver, no cargo and all fluids, including fuel) and the GVWR is Payload (Tongue weight becomes subtracted to payload).

Then there is the GCombinedWR, for the vehicle and trailer. Payload, including passengers, luggage, hitch-hiking mice, etc., must be included in this weight. Since most manfs set the tow capacity as GCWR minus Curb Weight, any part of the payload that is used must be subtracted from the tow capacity.

All of these WeightRestriction numbers are like links in a chain, so the first one nearing violation is the controlling restriction.

Exceeding or approaching the rear axle GAWR is handled by a WDH, to move some of that weight to the front axle and some to the trailer axle.

BTW, the trailer's GVWR seems to be usually set be the axle rating (and wheels/tires).

[Pete]

I just had the tongue weight of my 2008 Oliver Legacy Elite wieghed at the Bluebonnet Casita Rally.

Currently, my tongue is on the middle of three settings due to the added aluminum box I asked to be fabricated to accommodate my Honda 2000 generator. it is strapped down with two ratchet straps and secured with two lockstraps. Gas is full, I guess its about an additional 75 lbs of weight hanging out in front of the leveling jack.

Fresh water = 50% / Grey = 50% / Black = 29%.

Tongue weight = 400 lb.

After moving the tongue OUT to the final position tongue weight = 380 lb.

Proof positive that extending the tongue lessens tongue weight. Please don't ask for the nuclear physics behind how it works, I just read the numbers!

I understand about 10% of the trailer weight should be on the tongue and that if you get it TOO light you "may" encounter stability problems.

Tongue extended also provides an easier back up experience for some because it is less likely to over-correct when changing directions.

[Frederick L. Simson]

Since the Sienna is good for 3500 lbs, except for gas mileage, [b]we don't have to worry about items carried in the TV.

That's not how I read my Odyssey's Manual...

Originally posted by 2003 Honda Odyssey Owner's Manual
[b][b]Maximum Total Trailer Weight:
Number of Occupants-----------------------------------Equipped with transmission cooler
Including Driver*-----------------------------------------and power steering fluid cooler
-----2-------------------------------------------------------------3,500 Lbs (1,580 Kg)
-----3-------------------------------------------------------------3,350 Lbs (1,520 Kg)
-----4-------------------------------------------------------------3,200 Lbs (1,450 Kg)
-----5-------------------------------------------------------------3,050 Lbs (1,380 Kg)
-----6-------------------------------------------------------------2,900 Lbs (1,310 Kg)
-----7---------------------------------------------------------------650 Lbs (295 Kg)**
*Based on 150 Lbs (70 Kg) per occupant
**Weight limited to avoid exceeding rear GAWR

For every addition of a 150 pound person (or piece of luggage), the amount of trailer weight allowed is reduced by 150 pounds.

[Pete Dumbleton]

I think (hope) Pete means that he has enough excess difference between the trailer weight and the top limit of 3,500 lbs to not be very concerned about a little bit of stuf in the Ody.

Be nice to have actual weight of trailer at axle to go with tongue weight.

Frederick, that's a good chart, illustrating the relationship between GCWR and tow capacity.

GCWR minus CurbWt minus passengers minus cargo minus hitch gear equals tow capacity on trailer axle(s). An extra pound in the TV is one less pound for the trailer.

[Pete]

Pete,

Haven't actually been on scales but here's what I calculated . . .

dry weight = 2450
Water "stuffs"= 322
My items = 90
Cooking items, etc=110
Items on Tongue = 75
dog 13

total = 3060

Tongue 400 / Total 3060 = 13.07% of total weight
Tongue 380 / Total 3060 = 12.4% of total weight

The trailer towed perfectly the 930 miles back from the factory. No sway at all with trucks passing or wind buffeting 25 mph, sometimes a direct crosswind.

Gary, who did the tongue weighing at the Bluebonnet said most of the Casitas were well above 400 lbs with some coming in over 500 lbs tongue weight.

Pete

[Gina D.]

dog 13

[Sandra L]

I just had the tongue weight of my 2008 Oliver Legacy Elite wieghed at the Bluebonnet Casita Rally.

Currently, my tongue is on the middle of three settings due to the added aluminum box I asked to be fabricated to accommodate my Honda 2000 generator. it is strapped down with two ratchet straps and secured with two lockstraps. Gas is full, I guess its about an additional 75 lbs of weight hanging out in front of the leveling jack.

Fresh water = 50% / Grey = 50% / Black = 29%.

Tongue weight = 400 lb.

After moving the tongue OUT to the final position tongue weight = 380 lb.

Proof positive that extending the tongue lessens tongue weight. Please don't ask for the nuclear physics behind how it works, I just read the numbers!

I understand about 10% of the trailer weight should be on the tongue and that if you get it TOO light you "may" encounter stability problems.

Tongue extended also provides an easier back up experience for some because it is less likely to over-correct when changing directions.

Hi Pete,
Your website and pictures on the Oliver forum are enjoyable. What is your tow vehicle?

[Pete Dumbleton]

Sandra, do some research with the search tool on siennas; several very astute members have used them and there is lots of info.

Pete, looks like you are in the gray zone between 'Tow to the limit!' and '75% Rule' Keep an eye on it and you should be fine, but don't start a souvenir rock collection...