after I rebuilt my brakes a few years ago they never seemed that firm. I put this down to the rear disks needing to bed in to the new pads. The brakes were always good enough to pass the MOT and avoid the odd idiot that tried to pull out in front of me. But after the last MOT they started to get excessive travel. So I bled the brakes just as a test and even though I was thinking the master cylinder (which was new) maybe a fault. After bleeding the rears the brakes came back better than ever, really firm and strong. Bleeding the fronts had little effect. So I think the rears are letting air in some where. Over the last few years every part of the brakes have been replaced, the previous owned had two reconditioned rear calipers put on too. I've order a set sills for all the calipers, front and rear and will refurbish but I was wondering if there is any other way air could be getting in? I can not see any leaking of fluid at all and the reservoir is not emptying over time, as you would expect with a leek.