So I transfered forks and brakes from one frame to another. AFAIK the brake worked fine on the other frame. Wheels are different BTW.

Magura Marta’s – properly spaced around the rotor, Fox F100, Hope ProII…

I have pushed the pistons back evenly several times, I’ve given the caliper a proper clean with disc brake cleaner, applied royal blood to the inside of the caliper and then squeezed/pushed back caliper back again to try to lube it.

Still, one of the pads rubs and does not return like the other side does 🙁 Any other ideas greatly appreciated!

I am currently down to 1 bike so would prefer not to send it to the service centre to sort…

You have done the right thing – just do it a few more times. I would use the brake fluid ( dot or mineral whichever is right) as a lube

Have you tried ‘holding’ back the good piston while doing the above?

disc brake cleaner… doesn’t that stuff kill seals, as it it makes them expand? I may be wrong… I used to use it on my avids just to clean them. Ended with stuck pistons. I took the calliper apart; new seals, red rubber grease, never touch my brakes these days.

As per TJ and granny_ring. Only tip I can add relates to final caliper alignment once you’ve cured the stickiness. Here’s my tip (which has worked for me on Avids, Formualas, Maguras and Hope): get some very thin paper – thin & slightly glossy paper till receipts are perfect – then, with the pistons fully retracted and caliper bolts loosened off, slide a piece of paper between the pads and each side of the rotor. Then slowly pull the brake on hard and keep it fully on until you’ve snugged up the caliper bolts – if all has gone to plan (& the rotor is straight), you should have even amount of clearance on both pads.

HTH

Second the red rubber grease. Got juicy 5 been in weekly service for the last 4 years by servicing them yearly using rubber grease.

p.s. I agree with muckytee on the subject of brake cleaners. The Muc-Off one is the least worst one I’ve used, if that makes sense! But some of them don’t seem to agree with some makes of caliper seals.

bowglie, I’d avoid using that method unless the brakes are brand new with new pads. Any uneven wear on the pads or unequal movement of the pistons will mean everything is out of whack.
Better to take the pads out and centre the calipers by eye, such that the rotor is dead central in the middle of the caliper slot.

You can get silicon o ring lube in bottles. Pump out the slow piston most of the way coat with lube and pump in and out a few times. Always worth a go before stripping down a caliper

Thanks guys – looks like I need to try a bit more agressive lubing with mineral oil and see if that helps. No problem with alignment BTW as they are IS mount…

granny ring +1
hold the good piston back slowly pump the sticky one, clean off with brake fluid (i use a cotton bud to wipe around) then lube up (i use red rubber grease) then fully retract and align then you should be good to go.

have a look on the magura support forums – do a search. I had a similiar issue with my louise FR’s after they’d been left for a while. Just moved them by hand iirc a good few times to get the lubed again. It worked.

orangeboy, any links where to get the silicon lube you mentioned? Ta

Took the caliper off the fork and turned it on its side to really soak the piston in mineral oil. Pulled the lever and then pushed the piston back in while holding the other one in, adding more oil….
–> problem solved! Thanks for everyone’s help. Might have to look out for some of that red stuff though.

I’ve got a tube of Girling red brake grease but I’m not sure I’d use it on mineral fluid brakes, just in case it affects the seals. A drop of Shimano mineral fluid is all I’ve ever used.