Another trailer sway story

[AustinBoston]

I was driving home from the Transit Hub yesterday, and ended up behind an SUV with a TOAD.  He had a typical front wheel dolly with the front of a Toyota Camry on it.  After a bit, I was able to see the driver was towing with a late model Ford Explorer.

It was all over the road...classic trailer sway.  It didn't make sense to me, either.  The Camry was centered on the dolly, it's wheels straight, it wasn't leaning either way.  The Explorer looked in good condition, wasn't sagging, and didn't seem to have any trouble accelerating or stopping.  But the moment the driver hit 40 mph (yes, 40 MPH!) it started a slow, wide wag.  Long before reaching 45 (the speed limit), he was on his brakes.  At first it looked like they were doing it on purpose, but every time it started, they would hit the brakes, slow down and get it under control.

After about a mile, the driver turned right and I turned left...onto a road with a 60 MPH speed limit.  If there had been an accident, I would not have heard about it.

Austin

[campdaddy]

I'm wondering if it might not have been an aerodynamic thing at play. Perhaps the airflow over the TV at certain speeds and/or with the right wind conditions set up the right vortexes to cause the sway. Just a guess.