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From what I remember, there are three areas of stability…
One other factor is how much fuel is in the towing vehicle’s tank. Fuel weighs 5.8 to 6.5 lbs. Ethanol is 6.59 lbs. Diesel is 7.0 to 7.3 lbs. If a vehicle has a 20 gallon tank you mat see stability change as the fuel is used.
Of course the easiest way to make a trailer unstable is to simply put your car in reverse.
When I was in the Army, I had a signal group with a bunch of M151A1 Jeeps (pre Hummer) equipped with trailers. None of the guys in the section had ever pulled a trailer before. After I finished with them they were doing figure-eight races in reverse around two warehouses. The major I worked for freaked out until I got him into a Jeep. He turned out to be a pretty good competitor.
