A week or so ago I towed my new 16' side bath Scamp from Cool, TX. to Mobile, AL.
I set the balance up before I left at 165 lbs. The tow car was a 2009 VW TDI sportwagen wirh DSG transmission. I did have a small instability on the interstate when passed by a car hauler trailer rig, but at the next stop I checked the trailer tire air and added a little more. Since the tires
were not cold I added a little more then the recommended 30 psi.
From there on there was no other problem.
The next morning I set the air pressure and drove on to Austin from Lampassas.
From Austin to mobile on backraods and the interstate from Baytown at speed with absolutely no problem. This was the nicest towing rig I have experienced in 45 or so years,
Of course the VW is a pretty good handling car.
The VW lists 165 lbs as tongue weight and as a coincidence the rear of the car sagged 1 inch and the suggested towin package springs raise the rear end that same 1 inch,
Now then here is a secret - The toe car and trailer need ot be rigged so that they are level to keep the roll coupling favorable between the two.
The key to stability is a low polar moment of inertia in the trailer and a center of gravity slightly ahead of the axle
The weight on the tow bar is a function of the lever arm formed from the axle
to the hitch and the ratio of the length of the tongue to the location of the gc.
The longer tongue length reduces the load on the tongue without moving the CG rearward. It also makes the trailer more stable.
Studied from the main study made in 1979 indicated the lengthening the tongue as little as on foot made measurable improvement.
Of course youe experience may vary adn noone should tow woth a rig they are not comfortable wit.
Remember the secrets are keep the weight low and concentrated near the axle, Keep the center of gravity ahead of the axle and the load on the tongue reflects the location of the gc.
If the trailer is unstable it is likely that the mass is concentrated in the rear even though it is offset by weight towards the front. The balance point may be the same, but the polar moment is definitely not.
This means that if any oscillation is started the magnitude is greater and more difficult to damp. The only damping is provided by the hitch coupled to the rear of the car.
If the side walls of the trailer tires
are not stiff enough they add roll component to the yaw as well making the overall conditions worse.
The combination of the VW, Scamp with 165 lbs on the hitch, and the weight distributed correctly and concentrated near the axle. The VW has a negative camber in the rear suspension and is IRS. It handles well with or without the trailer.
Within ratings for the UK version VW (same as US, but VW USA won't rate the car for towing at all). 3300 lbs braked and 165 lbs hitch weight.
It tows great and got 25 MPG for the tow at highway speeds.In Tezas at 100 F. (into a head wind).