After some shennanigans trying to change to a new front disc, (which turned out to be bent) I’ve now reinstalled the original so I can still get out tomorrow. However I’ve now got zero power when I pull the lever. Pistons hardly move at all and the lever comes right back to the bars with no resistance. What could I have done to cause this and will it require a bleed? Or, (hopefully) is there a simple solution…

The simple solution IS bleed the brake. But if you can give more nfo it might help to get you up and running.
Which type of brake is it?

Have you disturbed the hose at all- i.e. undone any couplings etc?

Cheers – It’s a Shimano XT lever and calliper.

Did you push the pistons back while playing around? Could just need to pump the lever a few times to get the pistons into position. Or did you squeeze the lever when the wheel was off the bike? That would posibly mean some fluid got pushed passed the seal and letting some air in. In which case you would need to bleed the system.

Hope I made sense as I have a beers in my hand while typing 🙂

I don’t think I’ve disturbed the hose – definitely haven’t fiddled with any couplings. It has been been in the workstand minus the front wheel for a couple of days though.

what does “shenanigans” cover?

Did you force back the pistons or anything like that ? (check system for oil leaks)

(as a starter, if you’ve not touched levers or calipers, stand bike upright and tape/rubber band the levers to the bars overnight (in the brakes “on” position) – sometimes helps squishy brakes)

(but, wot he said up there – prob need a bleed)

Have you fitted new pads at all? You will have minimal stopping power until they are bedded in.

Pop a ziptie on the lever engaging it fully into the grip overnight, or pump & hold the lever (hold for 30sec’s, release & repeat – the lever should gradually start feel normal) this should force the errant air bubble that’s
entered your hose, back up to the reservoir

I did push pistons back following the Hope video advice from here: http://www.hopetech.com/page.aspx?itemID=SPG219

as one piston was dominant when applying the brake.

All seemed to be fine using the original rotor after following this. THen I removed the wheel and changed to a different rotor and adaptor which turned out to be bent, (hence the shannanigans part)!

THanks for all the advice guys –
Ambrose, the pistons don’t even move the pads at all at the moment.

I’m going to have to sort out a crying baby now but thanks to you all for the input. Will try the Z1ppy’s ziptie idea for now and get back to you in the morning.
Many thanks!

Is there any chance that the pads/ rotor combo have changed?

And as mentioned above, a good bleed sounds to be in order.

You’re pulling the wrong lever, pull the other one?

Hi Ambrose, It’s Kev. Where’s the ride this Wednesday?

Albino, if you have some mineral brake fluid to hand and a No.4 Phillips screwdriver you can push the brake lever up til the cap is level, remove the cap, pump the lever a few times, and add brake fluid to the reservoir. Then repeat until you see no more air bubbles in the fluid when you release the lever. This will act as a quick fix to remove most of the air that was in the system from the hose and get it back up out of the MC.
Then top up the MC and replace the diaphragm by rolling it into place pushing out excess fluid and replace the cap.
You might as well do the full bleed though as this procedure is half of it anyway.

Albino- Skyline speaks the truth, follow him.

Hi Kev- nothing planned as such, any ideas? Needs to be local-ish, Cwmtwrch- Penllergaer- Llangadog- Carmel area. Thursday is v busy for me.

Post on the facebook page would be best.