(I'm a BB7 man really)
Have managed to pull the lever in, on a bike with no rotor on the wheel. PAds totally in contact with each other. Now what - is there a screw/cap I should remove and then wiggle a knife between the pads, or what?
Take the pads out and use a blunt instrument, preferably plastic and push the pistons back in.
Try to push on the center of the piston.
Exactly as Goldigger says.
A plastic tyre lever will do it without damaging the pistons. I've used an old Park one and it seemed to be made for the job.
without needing to loosen anything first ?
Remove pad retention pin with long nosed pliers, then get the pads and spring out of the way to attack the pistons with a plastic tyre lever.
I get the bit about removing the pads; just wondered if I needed to allow any extra expansion space within the system - seems not ?
It's a closed system, it shouldn't have pulled in any additional air; the flexible rubber membrane at the reservoir compensates for the volume difference between new/worn pads ( or overextended pistons 🙂 ).
That being said, if you have a bleeding kit and some Shimano brake fluid, you could attach the funnel filled with a minimal amount of fluid to the lever before pushing in the pistons...
IF you've bled the brakes with slightly or very old pads in, or without the proper spacer, you may have too much fluid in the system to retract the pistons fully.
With the pads out, you should be able to lever the pistons back in by inserting a PLASTIC tyre lever and carefully applying force against the direction the piston moves out in.
If this really isn't working, don't force it, fit some bleed hose to the nipple and zip tie a freezer bag to it (to avoid unfortunate squirting of brake fluid in whatever direction the bleed nipple is facing) and release the bleed nipple a quarter turn or so. Â Then try levering the pads again. Â They should move easily this time and you should collect pinky red brake fluid in the bag. Â Once the pistons are zeroed home, close the bleed nipple again. Â You shouldn't need to rebleed unless you allowed a bubble to form and let it get sucked back in. Â If you're 'rock hard lever' fan you'll probably want to pump the lever a couple of times before putting pads back in and fitting the wheel (although if doing this you should really add some fluid as the method relies on being slightly overfilled)
Thanks all, I'll give that ^ a go
I don't have any oil, nor a bleed kit so hoping not needed. These were supercheap brakes that I'm intending never to crack open unless/until they fail (or I do something stupid to them). I'm a big believer in leaving brakes well alone (the only other hydraulics I've had was an avid juicy and it worked fine for a couple of years - after which I shoved it on the wife's bike and it seems still to be going fine)
You can probably do it without removing the pads by putting a tyre lever between the lip of the backing plates and twisting to push them apart. May need two levers, one on each side,
Official service manual content
Buy a new one it was cheap
