I tow with a Toyota 4-Runner which is a mid sized SUV. While it would
appear to be a good choice for towing I found 60 to be the limit
before sway would start. I believe the problem is that even though it
has fairly heavy suspension you can still induce sideways movement by
pushing with one finger on the rear of the vehicle. After trying every
solution I could think of I finally changed the trailer connector to
Al-Ko AKS 1300 Stabilizer, which works by pad pressure to the ball.

http://tinyurl.com/yvjhve


Towing is now stable up to the max speed of the vehicle, which with a
6 cylinder engine and trailer in tow is 85. While pricey at $250 for
the connector and special ball coupler it is cheaper than unwrapping
the car/trailer from a tree.