As per the title really - took the allen key to the bolt, gave it a tweak to get the thing moving as it had locked in place. seems to have snapped the fixing away from the tube though as the bolt just spins and spins now. It's really annoying as it buggers up the lighting arrangements, I could do with using a bottle battery on that bike, so if I can fix it that would be wonderful.
Frame is a Santa Cruz Chameleon circa 2002, and the "bolt" is plastic, if either fact makes a difference
over to you guys

