[SDWEltoro]

One of the first things about towing safely and preventing sway is making sure the tow vehicle's (TV) rear tires have a sufficient sidewall strength, and load rating. Most of the trailer 'weaving' I see in front of me is likely caused by the TV's rear tires sidewalls not being strong enough. A tower needs to make sure their tires' load rating is sufficient for the rear axle vehicle weight PLUS that weight of the front of the trailer being towed.

I am not an expert on the subject, but it happened to me once when I was towing a boat with an S-10 pickup I used to have. Had a very slight sway at speeds above 60 MPH. I had different tires with stronger sidewalls mounted and installed on the back of the pickup and it stopped the sway immediately.