Why are trailers engineered to have tongue weight?

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Lee Gordon

Lee Gordon

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Or, why are the axles on a dual axle trailer right next to each other creating a fulcrum instead of at both ends putting the wheels on the four corners? That would seem to get rid of a whole host of problems that get solved with $500.00 WD hitches. I've seen heavy duty utility trailers with wheels at the four corners so it wouldn't seem to be an engineering issue. It feels like it's done that way just because it's the way it's done.
Anyone know why?
 
I suppose it would work except the front wheels would have to be a able to swivel. If they didn't, they would scuff real bad going around a corner and would wear out in no time. Also the trailer would probably have to set quite a bit higher for clearances when the wheels swiveled.  I use to drive a 5 ton truck in the Army and towed a 4 wheel flat bed trailer with artillery ammunition on it. The front wheels were connected to the to bar and turned like a buckboard. You didn't want to try and back that up. So that wouldn't work with a camper.
Interesting thought though.
 
Having pulled both types of trailers, the 4 corner kind while in the military, I prefer the 4 corner type.  Rene's point on backing is valid and while I have back the 4 wheel type it is a whole different ball game and most people would not do it.  Even though I did it frequently, it was never pleasant.  Seldom did it with the 2 1/2 ton or larger trucks but used jeeps and 3/4 ton vehicles.

As to the reason for the current type, my guess is the problems mentioned by Rene and above as well as cost as in the 4 corner type the front wheels steer so much more hardware is required.  I believe there are also other engineering problems as space must be provided as in a 5th wheel for the wheels to make the turns as well as a possible higher center of gravity.  It is not an easy task to design and keep prices down for all the various floor plans.

Bottom line, it is the cost and the other problems alluded here and by Rene.
 
The engineers have it right.  If you every pulled a four wheel wagon you would know why it is not a good idea for a travel trailer.  Wagons tend to wiggle a lot and jerk the tow vehicle from side to side.  Without any of the TT weight on the back of the tow vehicle, it is a very dangerous condition. And it is many, many times more difficult to back a wagon than a trailer.
 
The reason for tongue weight and wheel position is also to eliminate sway.

I've towed corner wheel trailers and they all swayed at moderate speeds.

They work OK for farms and parade floats.....
 
On a similar note, I've seen many comments about European trailers being engineered to have very little tongue weight. Does anyone know how this works? The laws of physics still apply so how is it that our friends across the pond seem to make it work? I even remember a recent post about Jayco coming out with a European-spec model with low tongue weight. I don't get it!
 
When I bought my boat and trailer, it was set up to where I had very little weight on the tongue.  Made it really easy to hitch up, but was a bitch to pull.  It swayed all over the place.  I had to move the boat further forward and increase the weight to about 100# before it would pull easily and without sway.

Take your WD hitch off and load your trailer rear heavy and you will soon see what a problem that is.  Also try to back up your MH while towing 4 down and you find out what happens then also.
 
Ok, first: The paired v/s spread axle.

When you put wheels at the 4 corners it is no longer a trailer, it is a wagon, you have to articulate one pair of wheels or it is impossible to turn the beast.. Even with "Dual" axles (close together) when you turn the tires side slip.

By the way, at low speeds Wagons pull nicely (Do not know how they do at high speed, Never towed over 20 mph) but backing is a witch.  I can do it, or at least I have done it, but it has been a LONG time.

As for tong weight.. Helps to stabilize the consist (Truck/trailer combo).  Too little weight on the tong (or too much) and bad thigns happen with fishtailing of the trailer.
 
Joe...
Can you give an example of one of these low-tongue weight models?  European caravans are generally smaller and lighter than US models, so of course the tongue wight is less as well. That's not a design revolution - just size and careful attention to minimizing weight.

Here's a very nice one, but look at the specs for water tanks, battery, ceiling height, etc. Most US buyers would not be impressed.
http://www.elddis.co.uk/buccaneer/specification
 
My uncle, the redneck genius, built a wagon with both front and rear articulation. If you pulled to the left on the front the rear would turn to the right. It pulled like a dream at any speed with no sway. Backing up was a double cauldron witch..
 
With that setup, each wagon trailer does not transfer any weight to the unit in front of it when braking, so you must have the heaviest trailer in front and the lightest trailer in the rear.  Otherwise you will have control problems during sudden maneuvers.

While the wagon approach may work for a 6000 lb pickup towing a 5000 lb trailer, it will not work if the weights are reversed.  Most RV trailers weigh significantly more than the towing vehicle.

As others have mentioned, wagon trailers tend to be unstable, especially when there's more than one of them.  The professional drivers herding those rigs down the road have been specifically trained to avoid making multiple small steering corrections.  Most of us do that unconsciously, rocking the steering wheel back and forth slightly while going down a straight road, and this can set up a "crack-the-whip" oscillation that whips the rear trailer violently back and forth.
 
Gary RV Roamer said:
Joe...
Can you give an example of one of these low-tongue weight models?  European caravans are generally smaller and lighter than US models, so of course the tongue wight is less as well. That's not a design revolution - just size and careful attention to minimizing weight.
Click to expand...


Gary, no specific examples - just going by memory and what I thought I had read/heard. Perhaps I was misinterpreting "lighter tongue weight" as "lower percentage of tongue weight".
 
This is why I love this forum! I had not even considered what a PITA backing up would be when there's a pivot point at the hitch and the front axle. I'd spend all day just trying to get set up.  :eek:
As always, great discussion and I've learned something new.
 
I once saw a tow dolly similar to a car tow dolly, a two wheeled contraption set between the TV and the trailer.  Thinking about it, it has some potential until you want to back up!
 
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