Talk About Tongue Weight

[mstephens]

Trailers come with some tongue weight. In fact, quite a darn load of tongue weight. There seems to be an established thumb rule of something like 10% to 15% of the trailer weight. Well, on 6000# that range includes 150# of SLOP! Which is it, 600 or 750? Makes a big difference to the TV.

I have some questions about this. Has anyone purposely altered their tongue weight? Do double axle trailers need more or less percentage than singles? I would guess less, but that's only my intuition. Is it being set too high in order to cover the worst case?

As far as I can detect, the only purpose of tongue weight is to assure that as the ball moves up during driving conditions, that there is never a "negative tongue weight" (NTW). An NTW would lighten the rear end of the TV causing a loss of traction. Very bad. We never want that to happen. If the road were completely ruler flat, wouldn't you want ZERO tongue weight?

It's easy to see how various road dips and swales cause the trailer nose to rise and fall, or "rock" on it's axles. The displacement of this rocking will increase with speed. If we had an imaginary gauge to measure dynamic tongue weight, it would be swinging back and forth below and then above the static figure. Maybe like this: 300 to 900 with a static figure of 600. The idea of a heavy tongue is that no condition of road or speed should ever create NTW.

But if it is set arbitrarily high, maybe it can be backed off under certain controlled conditions?

[Bill M.]

I have been in a sway situation with 2 different trailers. A closed U haul and a flat trailer with lumber. I suspect that one of the reasons for having a good bit of tongue weight is to assure that the mass of the trailer is sufficiently in front of the wheels of the trailer so that the trailer does not push the TV in the opposite direction when it sways and thus increase the instability. My experience is that tongue weight is your friend.

[switz]

Even the trailer I tow behind my Gold Wing recommends at least 10% tongue weight and it is far more aerodynamic than even an Airstream as it was designed by an aeronautical engineer.

From my experiences, tongue weight is like a lead line on a horse, it provides guidance to the trailer. I have had a few exciting moments when I discovered the trailer I was towing diid not have enough forward weight and the the tail literally wagged the dog.

Your point of the axles and weights is interesting when one looks at the Classic 31' trailers weight specifications. The literature empty weight is 7,365 pounds without options. The literature tongue weight is 773 pounds which is roughly 10.5% of the empty weight. The literature GVW is 10,000 pounds and that tongue weight would have to increase to 1,000 pounds to maintain 10% loading.

However, in the twin bed model, there are two long storage areas on each side under the beds with both inside and outside access. There is a large storage area under the night stand between the beds with access from the rear of the trailer. Without much thought, one might store the 50 amp power cord and power adapters in the back of the trailer which would unload some tongue weight. The wardrobe and fridge appear to be centered over the axles. In addition to the rear storage just mentioned, there is a lot of storage aft of the wheels with the rear roof locker above the head of the beds and side roof lockers over each bedroom window and hanging closet space at the foot of each bed.

As a former pilot, the concept of a weight and balance calculation is not new. I wonder if on the longer trailers, one needs to spend some serious time in load placement and weighing the results on scales to ensure proper tongue loading?

Regardless of the front scale placement discussions in prior threads, getting that first weight at either the jack stand or the ball socket before adding or changing anything in the trailer and using that weight number and location as a baseline reference point would be a start. No matter how the trailer is loaded, one would not want less than the original weight at the original weigh point and would hopefully see it increase as stuff is loaded aboard.

Since I will use my existing Hensley hitch on the new trailer, I know that I am putting over a hundred pounds of steel at the ball socket which means in theory that I would have compensated for a 1,000 pounds of "stuff in the trailer that I might load aboard. But the location of my stuff if all forward by the sofa would add lots of weight to the front of the trailer (tongue weight) while if it all was at the back of the trailer, the fulcrum point of the axles would allow the leverage to unload the weight on the tongue. The added weight is still inside the trailer.

What are your real world experiences?

[Bill M.]

Instead of modifying the tongue weight of the trailer to fit the car, I would look at modifying the suspension of the car to have some travel left with the trailer attached. I remember the days when Airstreams were pulled with cars. And there was a whole industry selling air bags, air shocks, and helper springs. You basically had to add something to pull a boat. The cars had heavy A frame with coil springs in the front. Perhaps leaf springs and solid axle in the back. That setup might be more forgiving to severe overloading than struts.
I will admit I do not understand the european concept of vey low tongue weights for trailers. Maybe you need to look at what they do.

[mstephens]

My purpose for questioning tongue weight is that I am setting up my new TV, a Chrysler 300 S. I will be towing my 2012 Flying Cloud 25. As this is a sedan, I need to budget my payload carefully. I will only have about 1200 pounds to play with. If I could take 100 pounds off the tongue, FOR EXAMPLE, that would be a significant improvement in my payload budget.

Mostly, I am first wondering at first if this tongue weight is overly conservative to cover every conceivable circumstance? That's a common engineering approach. The question might be put like this: Under what circumstances would I want to INCREASE tongue weight, or DECREASE tongue weight? Surely the factory setting can't be "perfect" for ever TV, can it?

[mstephens]

Originally Posted by Bill M.

Instead of modifying the tongue weight of the trailer to fit the car, I would look at modifying the suspension of the car to have some travel left with the trailer attached. I remember the days when Airstreams were pulled with cars. And there was a whole industry selling air bags, air shocks, and helper springs. You basically had to add something to pull a boat. The cars had heavy A frame with coil springs in the front. Perhaps leaf springs and solid axle in the back. That setup might be more forgiving to severe overloading than struts.
I will admit I do not understand the european concept of vey low tongue weights for trailers. Maybe you need to look at what they do.

Bill,

Yes, modifying the TV is also on the plate. Apparently, I can install rear springs from the Magnum station wagon, which would have some nominally higher capacity. Not a bad idea, as springs are somewhat cheap. I am also looking into it.

[mstephens]

It's not obvious to me how tongue weight is directly related to sway. Sway occurs when a side force tries to rotate the trailer about the axles - e.g. "yaw." The methods of stopping yaw are to make it hard to move the ball from side to side. Those methods are relative to the TV suspension and any friction devices added to the hitch. Example: If you have a TV with almost no overhang, and you have stiff lateral suspension, and low profile tires, it will be very hard to induce sway. I can see that ZERO tongue weight might add to sway because it tends to life the rear of the TV, but it would seem intuitively that 500# or 700# would make no difference, all other factors being equal.

[dkottum]

We use a ProPride hitch which extends the tongue length of the trailer; effectively reducing the tongue weight carried by the tow vehicle receiver. This will vary depending on trailer length and loading.

Some trailers load heavier in the front, depending on where most of the storage is. For example a front bed Airstream has the largest storage compartment in front.

As mentioned above by Switz, weight and balance matters. Try to concentrate loads equally side-to-side over the trailer axles.

[FreshAir]

Originally Posted by Bill M.

Instead of modifying the tongue weight of the trailer to fit the car, I would look at modifying the suspension of the car to have some travel left with the trailer attached. I remember the days when Airstreams were pulled with cars. And there was a whole industry selling air bags, air shocks, and helper springs. You basically had to add something to pull a boat. The cars had heavy A frame with coil springs in the front. Perhaps leaf springs and solid axle in the back. That setup might be more forgiving to severe overloading than struts.
I will admit I do not understand the european concept of vey low tongue weights for trailers. Maybe you need to look at what they do.

....or perhaps use a 'dolly' or 'slimp' wheel as we did in 1952. The trailer, a 26' Pan American, the car a '48 Nash. Dad finally had to buy this dolly in Texas during our journey from Michigan to California on RTE 66. That's me doing 'my hitching' job.

Neil

[dkottum]

Not sure of why light tongue load allows sway. I have carried much lumber in my utility trailer for building our house. If the load hung over the back more than front, it would begin swaying violently at anything over 35 mph. I learned that tongue weight or speed could induce dangerous sway, and the amount of sway seemed proportional to those factors.

[mstephens]

Originally Posted by dkottum

Not sure of why light tongue load allows sway. I have carried much lumber in my utility trailer for building our house. If the load hung over the back more than front, it would begin swaying violently at anything over 35 mph. I learned that tongue weight or speed could induce dangerous sway, and the amount of sway seemed proportional to those factors.

Interesting. One answer is that when lumber hangs over the back, there is more leverage for inducing yaw. The mass/distance equation will show that the farther back (behind the trailer axle) the mass is located, the easier it will be to yaw the trailer. So, in your case you have two variables - 1) weight on tongue; 2) mass hanging some distance behind the trailer axle.

[switz]

That reduced payload is the huge gotcha of attempting to use an underrated vehicle for the job at hand.

One only needs to look at the truck industry and all the variables that must be considered in building a truck for a specific job. You will not see a single axle street legal dump truck with a 30' bed with 6' high sides full of 30 tons of dirt.

I have had a no trailer brakes scenario develop one time towing a heavy trailer. The truck brakes stopped the rig because the brakes were designed to stop a 20,000 pound combined weight vehicle.

When everything is working as it should, great, but what happens when their is a failure of a crucial component at an inopportune time?

You all be careful out there!

[mojo]

Originally Posted by switz

I wonder if on the longer trailers, one needs to spend some serious time in load placement and weighing the results on scales to ensure proper tongue loading?

Most Definitely! This is how I have managed to adjust weight and tow with my Touareg. Only a full size spare and some light weight bulky items go in the car. Generator in a sealed tub, propane stove and chairs go in the back of the trailer. Luckily the local co-op only charges $1 for multiple weigh ins on the truck scale.

[mstephens]

Originally Posted by switz

That reduced payload is the huge gotcha of attempting to use an underrated vehicle for the job at hand.

One only needs to look at the truck industry and all the variables that must be considered in building a truck for a specific job. You will not see a single axle street legal dump truck with a 30' bed with 6' high sides full of 30 tons of dirt.

I have had a no trailer brakes scenario develop one time towing a heavy trailer. The truck brakes stopped the rig because the brakes were designed to stop a 20,000 pound combined weight vehicle.

When everything is working as it should, great, but what happens when their is a failure of a crucial component at an inopportune time?

You all be careful out there!

Yes, on Manufacturer Tested Tow Vehicles, one can probably assume you have good enough brakes to stop the rig if the trailer brakes fail. We just don't have published testing on some of these sedans we are playing with. What we know for sure, is that the manufacturer doesn't test these vehicles for such towing circumstances. What would we learn if we did test them? That's the question.

Here's my intuition:
1. My 300 C has massive 4-wheel disc brakes. I have not a single doubt in the world it would stop my rig without trailer brakes from 60MPH in a very decent distance. No doubt at all. The brakes are approximately the same size as on my 1500 pound heavier Suburban.

2. With trailer brakes, it will stop shorter than my Suburban rig.

3. My 300 C will do an emergency lane change with the FC25 at a higher speed than any 3/4T truck in existence. Guaranteed!

Now, that's my intuition. I will have to test much of this to see if it is true or not, and I hope I can do some of that. I live in an area with a lot of long straight roads, and I think I can do some of this testing safely.

We have to ask 'what does safety mean when towing a trailer?' There are two arguments being made. First, big and heavy is safer because of axle ratings and tow ratings. It assumes that the risk people face is based on broken axles, busted wheels, and insufficient brakes. The alternate argument is that the safest TV is the one which handles best, drives best in emergency situations. This assume the risk is that you can't swerve out of the way of an oncoming incident.

Both are good arguments that can be made. It is not logical to assume that only the first argument applies. One of the reasons that European sedans became so popular beginning in the 1980s, was that their handling was so much superior to the big American sedan. Go back and look at those handling tests in the days of Road and Track and Car and Driver. These reasons hold true for any driving, including towing. Why should any tow rig handle poorly? It shouldn't.

Pickup trucks can clearly do some things sedans can't. Hauling sheets of plywood, or garden trees, or messy tools. That's a clear reason not to use a sedan. But I think towing is not one of those cases. If I stay under the axle and tire ratings, and balance the rig, and I have the power and brakes, I think I have the better towing rig in a super sedan. Of course, it is a debate. It's good to hear all sides, think of all angles.

I hope I can test some of these ideas. Maybe a shoot out? (LOL)

[mstephens]

Originally Posted by mojo

Most Definitely! This is how I have managed to adjust weight and tow with my Touareg. Only a full size spare and some light weight bulky items go in the car. Generator in a sealed tub, propane stove and chairs go in the back of the trailer. Luckily the local co-op only charges $1 for multiple weigh ins on the truck scale.

That will be our strategy too. We don't carry a tone of stuff even in the Suburban. Our on the road load is:

- 2 adults for 300 pounds
- 1 dog for 20 pounds
- lawn chairs for 20 pounds
- 2 bins for the hookup, like water hose, filter, mats, rags. call it 75 pounds
- Misc stuff like maps, 20 pounds
TOTAL: 435 pounds
I think 50 pounds of that can be put in the trailer. That would get the car down to 385 pounds before the tongue and hitch.

[andreasduess]

The brake argument is somewhat incomplete.

All vehicles are designed to come to a safe, controlled stop from their top speed, which is far higher than your typical towing speed.

For example, a Porsche Cayenne has a top speed of over 160mph. Bringing a trailer to a safe, controlled stop from 60mph, even without trailer brakes, should not be much of an issue.

The top speed of a Honda Odyssey is close to 120mph, with the brakes to match. The top speed of a Chrysler 300 is 155mph, same applies.

[Ganaraska]

Originally Posted by mstephens

My purpose for questioning tongue weight is that I am setting up my new TV, a Chrysler 300 S. I will be towing my 2012 Flying Cloud 25. As this is a sedan, I need to budget my payload carefully. I will only have about 1200 pounds to play with. If I could take 100 pounds off the tongue, FOR EXAMPLE, that would be a significant improvement in my payload budget.

Mostly, I am first wondering at first if this tongue weight is overly conservative to cover every conceivable circumstance? That's a common engineering approach. The question might be put like this: Under what circumstances would I want to INCREASE tongue weight, or DECREASE tongue weight? Surely the factory setting can't be "perfect" for ever TV, can it?

You have got hold of the wrong end of things too quickly. You MUST have tongue weight to make the rig stable, then you use a weight distributing hitch to take the load off the tow vehicle.

You now have a rig that is dynamically stable in terms of weight distribution with even load on the front wheels, back wheels and trailer wheels.

CanAm RVs in London Ontario is the specialist in setting up this type of rig. This video shows a Chrysler 300 towing a 34 foot Airstream through a slalom course at 45 MPH.

JAGUAR towing Airstream 300C Towing Airstream Freestar - YouTube

Their formula for setting up a rig is more or less as follows:

Very strong and rigid hitch receiver, set up so the tow ball is as close to the back bumper as you can get. A standard brand receiver can be modified by welding to turn it from an I shape to an H or K.

Good name brand weight distributing hitch with sway control. Do not go too heavy on the spring bars, 500 or 600 pound should be about right for your trailer.

Good brake controller

1 size smaller tires for better gearing and more stability. If your car came with 70 series tires get the same size but 60 series. If you have 60s, get 50.

Transmission cooler

Then set up the whole rig so the tow vehicle and trailer are level and weight is evenly distributed. This can take several trips to the weigh scale, weighing front axle, rear axle and trailer separately. But once you have it set up you merely have to duplicate the same settings next time you hook up.

[Ganaraska]

In case I wasn't clear... you need 10% tongue weight then the spring bars lift up the back of the car.

[mstephens]

You MUST have tongue weight to make the rig stable,
--------------------
How much?

[SteveH]

"In driving experiments with cars pulling trailers, the trailer c.g. position was varied by moving its load. Too much rear loading (or too little tongue weight) resulted in pendulum motions and instability. Experiments carried out and video recorded by Chief Engineer Olle Nordström (then my associate) at the VTI in Sweden.

Unstable caravan-auto jack-knife. Test by Olle Nordström. - YouTube