[Closed] SLX stuck piston

Hopeful bump?

Find something that will fill the rotor slot completely (like [url= ]this[/url]) and then find something that will approximately fill the space between the working piston and whatever you put in the rotor slot. Now pump the lever...

If it comes out, then wet the piston with some silicone lube or mineral oil (brake fluid). Push it back in, press it back out, and lube again. Repeat two or three times, push the piston back in and thoroughly clean and dry the excess lube/fluid away before refitting the pads and setting the brake up again.

If it didn't come out, then it may be best if you take the brake to a shop. It might just need a bleed, but it might be something more terminal. Impossible to say for sure without the brake in front of me.

Cheers for the help.

Have tried your suggestion, and the piston comes out, but when I go to push it back in, there seems to be more resistance than the other piston.

I've done this 4 times now, and still it refuses to come out unless I'm holding the other piston in.

Then I suspect that you're suffering a manufacturing/servicing fault. It might just be a slight twist on the piston, a damaged piston or a swollen/dry seal, but it's certainly something that needs a proper inspection. How old is the brake? Had much maintenance? Shimano hydraulic systems are entirely unserviceable, so if something has failed your only course of action is to replace. I'd suggest letting a mechanic get his hands on it and determine exactly what's gone wrong.

XT and SLX do seem to be a wee bit liable to sticky pistons, not terribly but a little more than I'd like.

Three_Fish's answer isn't really right, there's servicing you can do here. Pop out the piston, remove the seal carefully, clean everything thoroughly then clean it again, use a small pick (bent paperclip or ideally dentist's pick) to clean out any crap that's stuck in the groove that the seal goes in. Coat seal in mineral oil and reassemble, bleed up and see if it's still stuck.

If it's still stuck you run into a slight hitch in that Shimano don't sell the seals or pistons seperately and it'll be one of them you need. With SLX the calipers are 2-part, realistically the best thing to do is to but a caliper and just swap the whole thing, and keep the old one as a spare (as the good piston and seal might come in useful). The calipers are usually around £30 but they do come with a set of pads which would be £14 seperately.

Three_Fish's answer isn't really right...

Really? So I'm wrong that if something has failed the only course of action is to replace? And yet...

If it's still stuck you run into a slight hitch in that Shimano don't sell the seals or pistons seperately.

I didn't say that Shimano brakes can't be maintained, I even described minor maintenance in my first post. I would add to your maintenance instructions that care should be taken when removing pistons and seals. Especially on a brake which has had a lot of use, attention should be given to replacing the seal in the same position it was originally in. An old seal is almost certain to have been driectionally deformed by prolonged use and will invariably fail to work if replaced the opposite way round.

Three_Fish:

"I didn't say that Shimano brakes can't be maintained", o rly?

"Shimano hydraulic systems are entirely unserviceable"

"if something has failed the only course of action is to replace"

Hmm. You may have been [i]trying[/i] to say something different, but this is what you said, both comments completely misleading.

You may have been trying to say something different, but this is what you said, both comments completely misleading.

You might have a point if they had been two separate comments; but what you've actually done is split a sentence - putting, as it were, 2 and 2 together to get 19.

I used the term [i]unserviceable[/i] in the perfectly correct sense to mean [i]unrepairable[/i], and then proceeded to use the qualifier "so if something has failed your only course of action is to replace" to make this clear, just in case somebody came along and thought that I'd actually meant [i]uncleanable[/i] or [i]unusable[/i]. The only error I've made here is to assume that everyone would be able to understand my sentence.

"I used the term unserviceable in the perfectly correct sense to mean unrepairable"

Which is also wrong.