A friend of mine that also cuts grass recently looked at his 16ft trailers frame and side rails and noticed the vertical support pieces for the side rails on the passenger side in the rear of the trailer were completly cracked!! His trailer is only around 4 years old! We came to believe it happened as a result of constantly loading and unloading heavy mowers, when you run a mower on or off a trailer, you can see the back part sink down pretty much and the part behind the rear wheels has little support. I welded the pieces back together and added some extra bracing. I remember he once thought about adding some sort of drop down pieces that would drop to the ground when loading, but he never did. I am going to start watching my own trailer for this.