teessidewhite

Could anybody out there tell me what looks like a diaphgram fitted to the end of one of the two caliper carrier bolts on the rear disc brakes of my Astra 1.4 Exclusiv does? I also have a high pitched squeal from the drivers side rear wheel that is only apparent after travelling constantly for around 30-40 miles.Not sure if it could be a sticky brake binding. Thanks in advance. Dave Luke.