Please be careful when you are loosening the screw. You may have to unscrew it completely from the "steal ring" to slide the levers off the bars. On many levers there are little washers and spacers under this screw head. They drop out easy and are hard to put back in place. So if you have to unscrew it completely, apply a small amount of pressure from the screwdriver or key on the screw head until the "steal ring" is removed and then screw the ring back onto the lever