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I've come to use my hardtail, which hasn't been used in a couple of weeks, to find the front brake sticking. The lever pulls to the bar and then doesn't return and leaves the pads jammed on. Removing the wheel and pushing the pads back 'resets' the brake but as soon as you pull the lever again it gets stuck. A sticky piston? Needing a bleed? Any ideas?
The bike lives in the shed and is stored upright with the front wheel removed if that makes any difference, but has since been in the warm in the house which hasn't made a difference. M615 model.
Never had this problem.
But remember a POST in this forum which was discussing this issue. Didn't follow this post so. No idea if the "search" function works again after the forum software upgrade...- maybe try your luck!
Sticky piston: yes - Shimano had some problems with those. I never took the brake totally apart - but I think the pistons are from plastic (?) and this plastic might expand when there was lots of moisture around (?). Sounds very strange but that's what I heard. No idea if this is the problem with your brake and don't know either if it's possible to get a "spare piston"... - but I'am sure that older posts will have this discussed already.
Had it on my XTs, on the XTs there’s a ‘something’ in the lever that fails, a seal I think, but it may also be something the do with the bit point adjust which Deores don’t have but still.
Anyway it was borked, the replacement had about twice the lever stroke so I suspect it had been degrading for a while and I didn’t notice.
Frankly though, it doesn’t matter, if it can’t be fixed with a bleed you have to buy a new lever, they’re not really serviceable, but as they cost less than a lot of service kits it’s not a biggie in my book.
Ever used non-Shimano oil in them? That’s what did for mine I’m told.
"Ever used non-Shimano oil in them? That’s what did for mine I’m told"
Oh cripes! I'm using Manitou forklift mineral brake fluid in mine , will I die?
Don't think there'll be any benefit from bleeding the brake if it's a sticky piston.
Mobilising the piston by how you described "pushing the pads back" and then pulling the lever so the piston moves out again, keep doing this and hopefully this will mobilise the piston. This will ruin the pads if you are using a screwdriver to push pads back over and over.
careful not to push the pistons out too far that they come out completely!
Also if you have a bit of mineral oil you could put a bit on the edge of stuck piston to help lubricate.
it's worth a go if it's completely dead anyway
Good luck with it
“<span style="color: #444444; font-size: 16px; -webkit-text-size-adjust: auto;">Oh cripes! I’m using Manitou forklift mineral brake fluid in mine , will I die?”</span>
Yes, but probably not because of that.
I’m 95% sure using Halfords branded oil in mine caused the seals to fail within a few months.
I filled a set of Tektro Auriga's with bog standard LHM from the motor factors and over two years later they're still working lovely.
In case you are looking at replacements then JE James (I think) were chucking out Tektro Draco's for £12.99 per end recently. If they're as good as the Auriga's then definitely worth it.
I've used LHM in my deroes for years without issue.