This caliper is sticking and the quick release does not work. I tried lubing/cleaning the caliper on the bike, but it made no difference. The cable inner/outer is new and works properly. I have now taken the caliper off the bike to have a closer look. It seems like the rubber guide on the spring (see pic) maybe causing the sticking. It is making creaking sounds and seems to be stopping the smooth motion of the callipers. The pad bolts and caliper bolts were tough to remove, as was freeing the cable adjuster (I had to use mole grips!). There seemed to be oxidisation build up which I suppose is like rust. The thing is, do I need a new caliper, or can I save this one? If it can be saved, how best do I go about cleaning it and what can I do about the rubber guide?
