Ive noticed that the lever for the rear disc brake is sticking alittle (doesnt seem to spring back after applying the brakes) compared with the front. Is there something like a spring likely to be missing? Or is it going to be in need of some oil, grease, etc? Ive never really messed with bike disc brakes before, the bike Ive only had a few months and is obviously second hand. These certainly dont feel as good as my Hope M4/M6 and Magura HS33 brakes on my other bikes. I did change the pads on the back disc, if that makes any diifference? Help!