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Bad Bleed = Apparent Sticky Piston But It Wasn't.


dann2707

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Random topic but just thought i'd share my experience as it might help out others!

I kept having this situation where i'd pull my rear brake and the piston wouldn't return all the way back at all, usually one side only but it changed to the other side now and again.

This led to a horrible lack of confidence when gapping as the pad would catch on the rim ever so slightly and I didn't get that solid on/off feeling of the brake.

- At first I thought my clamps were too tight and was squashing the slave cylinders so I slackened them off and initially it appeared to have fixed it but the problem came back.

- Thought the pistons were just lazy due to me having the brake bled with water alone.

- When removed from the bike the brake pulled out and returned as it should which completely baffled me.

Got pretty stressed with it and completely ruled out a bad bleed as the pistons pulled out instantly and I had a solid lever feel with an 05 maggy + 4 finger lever.

I thought i'd give it a bleed anyway in the sink, I had previously just used a syringe on the last bleed, and it's completely solved the problem.

The cylinders are returning instantly when on the bike now and the confidence is back.

Hope this helps anyone, probs not haha.

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Yeah, what do you mean by only moved one piston? As in when you screwed in the tpa only one moved in, but when you pulled the leaver the one that was closest moved first, then when that one hits the rim the other one would come in? If so that's just how maguras work.

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Yeah, what do you mean by only moved one piston? As in when you screwed in the tpa only one moved in, but when you pulled the leaver the one that was closest moved first, then when that one hits the rim the other one would come in? If so that's just how maguras work.

Yes when winding the TPA in one piston would move, then when I pulled the brake the same one would stick out. Now, with a fresh bleed they centralise and distribute the TPA'd amount between the two cylidners which I thought was normal?

just checking. you were bleeding the brake with the tpa off yes?

Yup yup everytime. It was just a shit bleed that I had done with a syringe I'm presuming, Im a master of bath bleeds but awful doing a syringe bleed.

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That's really just how maguras (and vees) work. If you have too much adjustment on the tpa that's where you come into problems as one pad is always going to be really close to the rim.

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Im going through a similar situation at the moment having one piston a tad slower than the other which catches every now and then which is annoying me.

My set up is a 05 maggy with 4 finger lever, oil bled with echo tr clamps.

Gonna have to drain the full brake out clean it out with an airline give the pistons a good clean and a fresh bleed with oil. ( I daren't go for a water/bath bleed)

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You should Andy. Easy to bleed, awesome lever feel and rock solid lever feel!

This piston swelling shit takes ages to happen, and even then is easily solved.

The benefits far outweigh the (minor) issues that may arise.

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Because I do not want to? I'd rather stay original on methods.

Besides my brake is over 6 years old and has had 2 bleeds in it's time from new. So it's done it's job and shown some wear from the usage it has had.

Has anyone used different fluids in car brakes? Hope? Hayes brakes etc? With them running on dot 4. Would be interesting to know with people using the water bleed on mineral oil brakes.

Edited by Andeee
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Has anyone used different fluids in car brakes? Hope? Hayes brakes etc? Would be interesting to know with people using the water bleed on mineral orientated brakes.

Yeah you can use some Citroen oil, don't know the exact name of it... It's thinner than royal blood but that doesn't really interest me that much since water is the way to go. But I can look up the name for the oil if you wan't to :)

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That's really just how maguras (and vees) work.....

That's really not how Vees work! Unlike Maguras they actually have the adjustment to balance them on the spring tension of each arm, the whole idea of which is to ensure both pads hit at the same time and return an equal amount, if they're not, they need adjusting or there's something wrong.

The Citroen stuff's called LHM, which is just a different brand of mineral oil. Shimano mineral oil's also supposedly thinner. Car brakes Hope and Hayes brakes are all discs (or drums on cars I guess), and have to deal with heat that would boil water very quickly. It's no unheard of for people to bleed discs with water for trials use where they're not getting hot, but I don't know anyone who's done it long term.

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I don't know what you're getting at here haha

Ok, it's been a thing on TF that really annoyed me over the years, newbies come and post on TF asking why one of their magura pistons ways sticks out and barely moves while the other moves freely. Then you get 20 people with different advice on how they need to re bleed, re bleed with water, rebleed with oil. Need to lube the pistons, an a host of other things.

All that is happening most of the time is that they've got the bike with maguras, used the crap out of them and they just keep on turning that red tpa further and further. All the tpa does is push more oil through or it takes up the slack. Once the tpa has taken up the slack, any more adjustment is going to push one pad out only, it's very rarely going to push out both pads evenly because there's always going to be one piston that's free-er than the other. The more tpa the more that pad is going to stick out, and the closer it'll constantly sit to the rim.

Simple fix is just undo the tpa right up to the point just before it hits that slack point, then re-position the actual pistons and everything'll be fine.

That's really not how Vees work!

Yes, you're right, I take that back.

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Ok, it's been a thing on TF that really annoyed me over the years, newbies come and post on TF asking why one of their magura pistons ways sticks out and barely moves while the other moves freely. Then you get 20 people with different advice on how they need to re bleed, re bleed with water, rebleed with oil. Need to lube the pistons, an a host of other things.

All that is happening most of the time is that they've got the bike with maguras, used the crap out of them and they just keep on turning that red tpa further and further. All the tpa does is push more oil through or it takes up the slack. Once the tpa has taken up the slack, any more adjustment is going to push one pad out only, it's very rarely going to push out both pads evenly because there's always going to be one piston that's free-er than the other. The more tpa the more that pad is going to stick out, and the closer it'll constantly sit to the rim.

Simple fix is just undo the tpa right up to the point just before it hits that slack point, then re-position the actual pistons and everything'll be fine.

Yes, you're right, I take that back.

You sir have just solved my problem! Thankyou very much

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Yeah you can use some Citroen oil, don't know the exact name of it... It's thinner than royal blood but that doesn't really interest me that much since water is the way to go. But I can look up the name for the oil if you wan't to :)

the citroen oil is called "LHM + (LHM plus) its green and its cheaper then Royal blood, its also a mineral oil like royal blood, but you must make sure you get all the royal blood (blue in colour) out before bleeding with LHM + as it doesnt mix (like water and oil doesnt mix, i work in the motor trade so get it cheap, but i allways use Royal blood as its whats recommended buy Magura, (even though car manufacturers change the 'recomended' brand of oil every year or 2 (only due to who there on stop with at the time of manufacture) you could argue you could use any mineral oil, which is partly true, as most people use any fluid in a Magura, water, anti-freeze, corn flour etc etc)

its a pre-filled system so aslong as it doesnt compress any fluid is fine ;)

What dragged me to this topic is because my mates having this problem, we bled it 4 times with royal blood and slave which only has the cross over attached and you bleed it from (not the cross over and the main realy long hose going to the lever) sticks, but after a few pumps it free's itself and works fine, until you leave it a few minutes and it sticks again :S which doesnt leave much confidence, whilst on a ledge and you need the brake to hold whilst about to gap......

we cant work out why, unless the slave needs replacing??

Maguras are EPIC when they work, but a PAIN IN THE A*** when they dont (Y)

P.S. mines fine though :) bites when the lever is pulled in about 3mm and sounds LOUD AS F**K!!!! (just the way we like it)

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What dragged me to this topic is because my mates having this problem, we bled it 4 times with royal blood and slave which only has the cross over attached and you bleed it from (not the cross over and the main realy long hose going to the lever) sticks, but after a few pumps it free's itself and works fine, until you leave it a few minutes and it sticks again :S which doesnt leave much confidence, whilst on a ledge and you need the brake to hold whilst about to gap......

we cant work out why, unless the slave needs replacing??

Define sticks. Does the slave retract all the way back?

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Define sticks. Does the slave retract all the way back?

you pull the lever and one piston moves instantly and the other doesnt, it moves say after the lever is half in ... then after few pumps they both move together

Edited by stunt man t
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