Can't get the pistons to come out of caliper...

felix.london

Just received a shiny new set of SLX brakes from ze Germans so swapped the levers 'round. The front brake is spot on but the rear one is having the above problem.

With caliper and pads removed - when I pump the lever the pistons come out slightly (not even enough to engage pads to rotor when installed) then go back again. Multiple lever squeezes should bring the pistons all the way out, no?

There doesn't seem to be any air in the system and when I push the pistons in with a tyre lever the reservoir overflows (slightly)

Any clues?

Cheers

nicklouse

refit and leave with the lever applied.

Zip strip, rubber band. inner tube.

felix.london

Reservoir open or closed?

nicklouse

felix.london wrote:

Reservoir open or closed?

makes no difference other than potentioally getting air into the system.

but why ask?

felix.london

OK. Everything re-installed and lever applied with cable-tie. What now?

bails87

Now....we wait.

felix.london

Btw - there is zero resistance in the lever if I that was not clear from my initial post. Zero resistance and the pistons come out maybe 2mm before returning.

cooldad

Leave it overnight.

nicklouse

felix.london wrote:

Btw - there is zero resistance in the lever if I that was not clear from my initial post. Zero resistance and the pistons come out maybe 2mm before returning.

well if there is nothing for the pads to press on then yes there will be no resistance.

felix.london

Of course. And what is happening while the lever is engaged over this period?

nicklouse

allowing the seals to set themselves. as it is them that controll the return movement of the pistons

felix.london

OK. And is this due to some error on my part when swapping the levers around?

nicklouse

no idea. did you bleed the brakes according to the manual?

EH_Rob

He may not have bled them at all - I swapped my XT levers around without needing to and they're fine...

felix.london

I only bled the rear because it wasn't working so presumed I'd got a load of air in the system

Followed these instructions;
http://www.shimano.com/publish/content/global_cycle/en/us/index/tech_support/tech_tips.download.-Par50rparsys-0008-downloadFile.html/02)%20Brake%20Hose%20Trimming.pdf

And like I say the front worked perfectly

cooldad

felix.london wrote:

There doesn't seem to be any air in the system and when I push the pistons in with a tyre lever the reservoir overflows (slightly)

Any clues?

Cheers

This would happen with air in the system anyway.