What is trailer sway, and how can you prevent it? Trailer sway is when your trailer starts to move side-to-side, dangerously out of your control. One of the most common causes is an incorrect weight distribution. By following the 60/40 rule, as shown in the video, you can prevent trailer sway. #UHaul #TrailerSafety #UHaulTrailers #MovingTips #Safetytips