Take them off, give them a clean, make sure the taper is ok, wack a little bit of grease on the taper, put some locktite 242 or 270 on the bolts, put the bolt on, torque the bolts up to the correct torque setting (i think its 8Nm for if its an m6 bolt) Leave for 20 mins to let the locktite set....and bobs your uncle!