ST mirrors are designed to bend over when bumped, then the internal spring brings them back. if they a pushed too far or bumped alot, they get a little loose feeling. unfortunately, you cannot replace the spring, you have to buy a new mirror. some other options are to reseat the rubber gasket at the fairing so that the thin edge is up around the mirror stalk; if you look closely, they usually are not seated after being bent over. this is kind of a pain and usually requires a sixpack and/or friend to share in the miserable job of taking the upper inside fairing apart to get at the mirror mount. if they get real loose, put a home depot self tapping screw into the bottom of the stalk near the fairing gasket. preferably on the bottom, and use a small, short, black one. although, even when they feel loose to the touch, they still seem to stay put at speed, maybe a little more vibration. this makes the flashing blue lights stand out better, but does make the unlit light rack a little hard to see prior to ignition.