How To: Lazy Pistons.

[Dan6061]

Noticed a few people moaning about having a lazy piston, so I've made this guide to sorting it out.

Mind the crappy photgraphy. I was rushing..

Lazy Piston: When one pad wont come as far back as the other, and usually rubs on the rim.

Right then...

YOU WILL NEED:

A track pump - Link to picture

5mm allen key

3mm allen key

8mm Spanner

5mm/4mm allen key - Depending on mount bolts

Bleed kit - especially the hosing and hose connector!

Oil

Mole grips/pliers.

WD40/GT85

______________________________________________

Right then...

1. Take the Magura off the bike. - I'm sure you know how, take off bar-end, grip, slide off lever. Undo mounts, and cut off any cable ties or anything holding the hosing on your frame.

2. Take it apart.

Please note: Be sure you're confident with bleeding it once you're done!

Undo the bleed bolts, and then the hosing.

Make sure you don't make a mess with all the oil/water going everywhere!

3. Now all that's off, you'll have the two pistons/slave cylinders on their own.

4. Take on, and attach the bleed kit hose to it. And the other end of that hose, you attach to your pump. - As you would a shraeder(car type) valve.

And pump the pump.

This should blast out any crap in the piston. It's handy to get the mole grips and clamp the nipple, then turn it so it's against the 'sticky out' bits of the slave cylinder. - This will pull the piston out a bit.

Also spray some WD40 all over it, in the hose holes, and on the piston.

Even fill up the clear bleed kit hose with WD40, and pump it through.

Do this like a mad man untill you're happy with it.

Then do the same to the other one.

5. Now that's the slave cylinders sorted.

Might aswell clean out the lever.

Take it all apart. - Undo the lever bolt, and out it all comes.

You can kinda see it, but there is a lot of oil and general crap around the bolt hole.

Just ridse it with water, and scrub it all off.

6. Don't be thinking that's it with the lever!

Remember what you just did to the slave cylinders? Do the same to this.

Fill it up with oil through the bleed bolt hole, and pump it a bit. - This will lube it all up.

Then attach the hose+pump to it, and pump away!

Once you're happy with that, put it back together.

7. Now you've got all that clean, you need to bleed it.

I tried the ol' "assemble it in the bath technique, but that didn't work.

You can try it, if it works.. I hate you, but well done. Ignore the rest.

Like me, if it didn't work, try this way:

With the whole of the brake apart, run a bath. Get it pretty deep, and chuck all of the brake in.

Make sure you ask before doing this, I didn't, and got moaned at.

(It'll leave a dirty ring around the top of the water)

Knock it all about abit, and watch all the bubbles come out.

Start putting it all together, except for the two bleed bolts.

Once you've done that, fill up your syringe *(if you don't have one, scroll down a bit)

Attach the bleed kid hose to it, and attach that to the bleed hole in the slave cylinder.

Slowly pump that, untill no more bubbles come out.

Then put in the lever bleed bolt, and do it up.

Take out the syringe, and put in the bleed bolt.

Now pump it, if the pistons come out at the same time, you're sorted.

Now go put it all back on, and it should work perfectly.

*No syringe?

What I did, is attached the bleed kit hose to the lever, and then kept the slave cylinder underwater.

Watching the clear hose carefully, start sucking.

Once you see the water coming through the clear hose, suck very slowly, or hold it, and put the bleed bolt in the slave.

This will hold all the water in, so you can undo the bleed kit hose. - Safer to do this underwater, to make sure no air gets in at all.

And do up the bleed bolt.

Lovely.

Sorted.

If you're having trouble, or didn't understand any of that - Either talk to me on MSN (Address in profile)

or post.

[531joshua]

Hey. I found that very interesting, and although my Magura HS33 is fairly new, I'm sure this will come in handy when it starts to age a bit. Really good of you to put the effort in. Well done!

Cheers, Josh.

[GTF]

Good post May become handy sometime

Edited December 7, 2006 by GTF

[joe b]

That's proper helpful, mate. Will definately need sometime .

Cheers,

Joe.

[Tylerlovesalex]

Thank you very much mate just fixed a old hs33 with that post cheers!

[munkee]

Surely you want silicon spray rather than wd40

[Dan6061]

I only have WD40, does the job.

[JT!]

I still don't think you need to do any of that to stop a lazy pistson. Just run your brake without any or little TPA.

[Walleee]

yeh I kinda agree with JT.

ANY magura i've ever had has worked as if it has a 'lazy piston' but I really don't see this to be a problem. The way the system work's is that once one pad is against the rim the pressure then get's transferred to another caliper.

The only way to get two pistons perfectly synchronised would be to tave exactley the same co-efficient of friction on both cylinder's, something which while is possible, would be a waste of time when the brake work anyway (certainly from my experiance anyway) I would imagine even then, one cylinder would hit the rim just before the other.

Having said that I see where you coming from wiith this topic but I think it's just a little too far, even for me.....

[anzo]

Does WD40 not corrode seals?

[bikerbob]

I don't think WD40 is a strong enouogh solvent to actually dissolve the rubber. I have heard a few people being concerned about WD40 corroding your crankcase seals on the moto trials bikes, but I had a look in the hopeless manual for my beta, and it actually reccomended putting a bit of WD on fork seals with no worries, so I reckon it's probaby OK.

I use WD40 on my stator and all over my crank case seals with no worries. If in doubt use duck oil or something.

The problems arise if you start using a non mineral based (DOT brake fluid for example) in them.

Bob

[PaRtZ]

Very good guide, thanks alot

[Greetings]

Personally, I wouldn't use WD40 on any element that would require lubrication. WD40 washes away all lube and is more of a cleaning thing. As good as it may be for fixing seizures, this isn't really what you should spray a piston with. I guess even engine oil would be better for this purpose, best thing you can lube it with is silicone spray or silicone grease.

edit: WD40 doesn't corrode the seals of the HS33. I know many people who run it as brake fluid and it works beautifully Great guide though!

Edited December 24, 2006 by Inur

[JT!]

ANY magura i've ever had has worked as if it has a 'lazy piston' but I really don't see this to be a problem. The way the system work's is that once one pad is against the rim the pressure then get's transferred to another caliper.

The only way to get two pistons perfectly synchronised would be to tave exactley the same co-efficient of friction on both cylinder's, something which while is possible, would be a waste of time when the brake work anyway (certainly from my experiance anyway) I would imagine even then, one cylinder would hit the rim just before the other.

[the666ers]

Whats the point in having a tpa if you aren't/can't use it?

Good guide I thought, nice one.

[JT!]

Whats the point in having a tpa if you aren't/can't use it?

You can to some extent, but it when it's like 5 or 6 turns it's where the trouble starts.

[fyfey]

I've heard if you want both pistons to move at the same time you can use a splitter:

[Netherking]

Just bled my rear brake for the first time. at first it looked bad but got the combination of opening, pumping and locking the system down after a few tries. but got it sorted. Just had to repeat the process about 5-6 times (going from one bleed bolt to other) but in the end i have a water filled sharp non-lazy brake. (i used the bucket/bath method)

Cheers

Harry

[Davetrials]

just thort id say instead of sucking shit in to your mouth, you COULD just blow.

[fyfey]

Nice guide. Had to use it today on a second hand HS33. Was clogged up with loads of gunk! The cylinders were sticky and full of thick black oil. I've cleaned them up good using this method, clean as a whistle and bled perfectly (using a syringe).

[JT!]

I've heard if you want both pistons to move at the same time you can use a splitter:

I've head they cause more problems than they solve. I supsoe if you know what your doing (unlike me) they should be ok.

I'll say again, little or no TPA = no problems.

[SemteX]

Ok, digging up an old topic instead of making a new one. Thought I might as well sort my brake out an shizzle before I get riding again when my ankle heals soooo...I've done all the stuff in the guide and one of my calipers is working perfect buuuut the other caliper is still a twat.

I can grip the nipple with pliers and pull it out, then when i let it go it will hit a point and return very slow (when it is all attached together AND when it's just the caliper with no water/oil in). I've laced it with WD40 on the piston and inside the holes, blown all shit out with air etc. Is there anyway to pull the whole thing apart to give it a better clean? I really can't be arsed buying a new piston or whatever and aint got no spare ones because all the prongs/nips have snapped.

Suggestions?!

[N Roach]

Just tested a few oils, GT85 will make your pistons stick, 3 in 1 oil will work a treat.

[bikespace]

Well it may be controversial, but today I've put a 60/40 mix of water/vodka in my lads HS33's. The brakes are brilliant, so I've just got to wait and see if there are any side effects. I suspect not.

The vodka was based on how hard it is to freeze vodka - ideally I suppose I'd have used neat alcohol, but I don't have any lying around the house, so vodka it is. I have plenty of that

Get the cheap stuff and it's not much more than de-ionised water Wouldn't like to dring too much of it, but for brakes it seems ideal

Now I realise how little has gone from my bottle of water/vodka mix after flushing and bleeding the brakes, I may try neat vodka in the old Monty, just to see how that compares. I'm sure that would never freeze.

Edited October 25, 2008 by bikespace