its a mine field, you think you are doing something for the greater good and it comes and bits you on the ass! the other day i decided to flush the brakes and while i was at it fit new bleed nipples to the callipers as the old ones had seen much better days. i ended up spending an hour trying to get a new bleed nipple out of the calliper because it had chewed it up! in the end i put to original one back in!