URGENT Disc brake newbie mistake -- help!

def_defyr
def_defyr Posts: 93
in Workshop
So you can probably see where this is heading...

I've just got my first disc equipped bike, with Campy Potenza.

Last night I was changing the rear tire and absent mindedly grabbed the rear brake lever...decades of habit...Whap! Pads closed, pistons engaged, but no disc between them...

So, how to pry apart safely? (Thankfully I did this at home and not on the road!)

Should I try to slide a putty knife between the pads? It's really tight. Or, can I remove the pads and press on the pistons directly to retract them (This seems risky)?

If I can get the pads just a few mm apart I think I can jam in the travel protector to wedge them the rest of the way open.

Thanks in advance, and lesson learned.

Comments

  • veronese68
    veronese68 Posts: 27,810
    Wiggle them apart a little starting where there is backing plate but no pad material, that should give a little space so yo can get something soft between the pads and then prise them further apart.
    Kinesis Pro6
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  • def_defyr
    def_defyr Posts: 93
    ^^Thanks. I think there's a little border around the pad material, will see if stiff putty knife or small screwdriver will do the trick.
  • reaperactual
    reaperactual Posts: 1,185
    Removing the bleed port screw on the lever before trying to separate pads/pistons will help if there is a lot of resistance and less chance of damage. Put a cloth over the port in case of any fluid drips and top up if needed.

    You could remove pads and push pistons directly with care using something plastic, a tyre lever works well.
  • def_defyr
    def_defyr Posts: 93
    ^^thanks, I've got some teflon ones that shouldn't damage the pistons.

    If I remove the bleed port screw, wouldn't that potentially let in air? Or is it a one-way valve?
  • plodder73
    plodder73 Posts: 326
    No it won't let air in and you only need to do that at all if the pistons refuse to move. Assuming the fluid level has not been topped up for any reason there should not be a problem moving the pistons without removing the port screw.
  • reaperactual
    reaperactual Posts: 1,185
    def_defyr said:

    ^^thanks, I've got some teflon ones that shouldn't damage the pistons.

    If I remove the bleed port screw, wouldn't that potentially let in air? Or is it a one-way valve?

    Air will be pushed out by the fluid returning to reservoir and reduce the effort needed to recess the pistons. That's the way I have done it numerous times not because the pistons 'refuse to move' because it's the easy way.
  • def_defyr
    def_defyr Posts: 93
    Thanks, all. I was able to wedge in the tip of a plastic putty knife enough to get space for the travel protector, which itself is wedge-shaped, so was able to push back the pistons...

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