I have mine on a rigid framed 'commuter/fitness' bike (08' Raleigh Detour Deluxe) and they haven't moved a bit from where i originally positioned them. Even after a spitirted ride on a greenway with plenty of places where the pavement is buckled from tree roots they are right where i aimed them. I have them sticking straight out so they look like the back of the Starship Enterprise from Star Trek. I think that if they began to slump I'd just find a position i liked and add a drop of PVC cemet to 'weld' the ball joint into place. For the price, even if you had to rig up a solid mounting as opposed to using the ball joint, they would still be a heck of a deal.