Bicycle Tutor

Hi,

I went to replace the pads in my rear brakes last night. I have shimano alfine s500 calipers. When I tried to reset the calipers I used a hard plastic tyre lever, same as I did with the front brakes... but the calipers wont move right back. They seem to be stuck. I've got the reservoir cap off at the brake level and when I try and push the caliper back you can hear a slight noise from the reservoir (as I'd expect when doing this). I can move them about 1mm then they just go back, essentially meaning I cant put new pads in. Any thoughts/suggestions would be appreciated.
ta

It sounds to me like your pistons have been pushed beyond the cylinder walls and air has gotten into the system from the worst possible place. If I'm reading you correctly, you are looking at a full flush of the system. That noise that you hear is bubbles - trapped air.