Hi folks,

Please forgive my childish questions but im new to hydraulic discs and have gotten myself in a spot of bother.

I have a pair of Formula RX 2012 that I removed to clean. I stupidly pulled the lever when the caliper was off and now it is back on, the pistons are preventing the wheel from turning by forcing the pads against the disc.

I have tried gently(ish) to push them back and have had some success but don’t want to damage anything.

Short of bleeding them, is this fixable? I’m stuck at work if not!

Thanks in advance. x

Pop the wheel out and then push the caliper pistons back in.

BE CAREFUL!

Don’t scratch the cylindrical surface of the piston and make sure you push them in square to the bore. If you don’t they can jam in the bore.

Oh – also put a little bit of the hydraulic fluid on to the cylindrical surface of the piston. This will make it easier to push in and give smoother operation when they’re back on the bike.

Hi JAG, thanks for that.

That’s what I did, but there was too much resistance for me to want to push them any harder, and they’re still not fully in.

Is this the ‘normal’ way of doing it?

Thanks for your help.

Yeah all perfectly normal….

but do be careful of getting them cocked over in the bore they will jam and if you force them you’ll damage the piston or caliper bore.

If they’re still resisting then take the cap off the fluid reservoir on the handlebars and then do it again.

No cap on Formula RXs, it’s a contained system- need a T12 torq and ideally the bleed kit to mess with them. Shouldn’t be neccesary though.

Find something to protect the pistons- doesn’t need to be much, stiff cardboard will do (in an ideal world, old brake pads). Then lever them back with something leverey- I’ve got a mahoosive old screwdriver for the job, some tyre levers work well too. Careful to keep them straight, apply force evenly not near the edges. Then, once levered back, leave it for a little while with the lever still in (otherwise, they’re likely to “bounce back” a little and tighten up again)

Thanks for the post Northwind.

I’ve had another go and the pistons are now lovely and level, but now both levers feel horrible and spongy, with loads of movement.

I guess this means they need bleeding then?

Could be… Sometimes all the movement dislodges air that was previously stuck somewhere out of the way, like in the reservoir- sort of like when you turn your bike upside down and the brakes die? Anyway, this doesn’t mean that they suddenly need bled, it means they always needed bled but it just wasn’t a problem yet 😉

You could try just tying the levers back to see if that returns them to normal… But it’d be better to sort the underlying issue tbh, it’ll get you some other time.

Nice one, cheers for that. 🙂

They should reseat themselves after you refitted the wheel. Since you pushed back the pistons they will be further away from the disc than before. This should be cured by a few pulls of each lever.

If this is not the case then as already stated it may have dislodged some air bubbles which need to be bled out. A simple process identical to the Avid procedure:

http://www.epicbleedsolutions.com/resources/videos/

I had to do this traiside recently, cracking the banjo bolt open a quarter turn to let a tiny drop of fluid out did the trick in the absence of a tiny torx key