Trailer does not add stability at all. Sidecars come in two flavors, ridged and articulated. The articulated type allows the bike to lean, so does not add stability. A rigid sidecar allows the bike to stand up by itself. You need to take turns very slow until you get the feel for it. I have never drivena muscle powered sidecar rig, but have 10's of thousands of miles on a 750 Ural. It is the only motorcycle I have ridden that allows me to scare myself without breaking the speed limit.