bleeding shimano brakes

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NUKe
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bleeding shimano brakes

Postby NUKe » 12 Mar 2018, 11:54am

I need to bleed my Shimano brakes, So I have bought the Shimano bleed Kit (plastic funnel ) As it was labelled as kit but it said Oil not included I assumed it had everything else. Although it appears from the comments section on the Chain reaction Q&A I may need a plastic tube?
Has anybody bought one of these and confirm what is in the kit
http://www.chainreactioncycles.com/shim ... -prod34710
I had assumed it would have the Syringe the pipe and the spacer required.

I have an old contaminated pads I can use as spacer not ideal, I can probably get a syringe from the Pharmacy on the way home.
Actually thinking on this I assume I can do it the same way as you would for car so just the tube,

If I do need a pipe what is the bore. ?
NUKe
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Brucey
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Re: bleeding shimano brakes

Postby Brucey » 12 Mar 2018, 12:05pm

if you read the Q&A 'how does it work?' question in the CRC link I think your queries will be answered.

FWIW you could bleed the brakes with just the funnel and the fluid, provided the funnel fits your MC, and you are happy/able to pump the fluid using the MC and back to the MC by pushing the caliper pistons back.

I would suggest that if you think you might ever want to bleed other brakes, investing in a universal bleed kit (eg the one made by epic solutions) might be a good idea.

cheers
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Cugel
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Re: bleeding shimano brakes

Postby Cugel » 12 Mar 2018, 2:28pm

NUKe wrote:I need to bleed my Shimano brakes, So I have bought the Shimano bleed Kit (plastic funnel ) As it was labelled as kit but it said Oil not included I assumed it had everything else. Although it appears from the comments section on the Chain reaction Q&A I may need a plastic tube?
Has anybody bought one of these and confirm what is in the kit
http://www.chainreactioncycles.com/shim ... -prod34710
I had assumed it would have the Syringe the pipe and the spacer required.

I have an old contaminated pads I can use as spacer not ideal, I can probably get a syringe from the Pharmacy on the way home.
Actually thinking on this I assume I can do it the same way as you would for car so just the tube,

If I do need a pipe what is the bore. ?


You'd be better to buy the full Shimano bleed kit. It has all the bits you need to move the mineral oil both up and down the hoses. And to keep the calliper pistons from coming out too far, or oil getting on the brake pads.

You need to push the oil both ways in the hoses, when installing or renewing it, if you're to get all the air bubbles out. The syringe (with connecting tube) pushes the oil (with any air bubbles) up from the calliper whilst the cup allows you to squidge air bubbles out from the lever cylinder, as well as collecting the excess bubbly oil pushed up by the syringe.

You can also use the syringe to suck oil down the hoses: bubbles sometimes lodge at the calliper end rather than rising up the hoses. Gravity alone (acting on the oil in the cup at the brake lever) won't necessarily put enough pressure on the column of oil in the hose to drive out bubbles at the calliper end, especially for the back brake.

Once you have the oil in and de-bubbled as much as you can, it is necessary to periodically repeat the cup-attach and lever-squidge to get the last few tiny bubbles out as they migrate up the hoses and into the brake lever cylinder. You'll get optimum brake feel after doing a couple more of these cup-only squidges (no syringe at the calliper end) perhaps a week then two weeks (and maybe three) after the initial loading of the oil into the hoses.

It's surprising how little air in the system it takes to make the brakes feel too squidgy at the lever.

After final de-bubbling, the hydraulics should work for a good while before you're tempted to renew the oil or the levers begin to feel less firm in their application of the brakes. Shimano give a recommendation for the renewal period but I can't remember what it is.

Cugel

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NUKe
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Location: Suffolk

Re: bleeding shimano brakes

Postby NUKe » 13 Mar 2018, 9:28am

Thanks guys gone back to the Start and ordered the Universal Kit, the Shimano kit is Misleading you would think in the Description they could call it something better, Shimano brake bleed kit suggests it has everything. new kit should be here Wednesday.
NUKe

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NUKe
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Location: Suffolk

Re: bleeding shimano brakes

Postby NUKe » 14 Mar 2018, 10:11pm

In the end didnt need the new kit. Just used the funnel and pumped the lever. All right and working now. Air bubbled out.
NUKe

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Eyebrox
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Re: bleeding shimano brakes

Postby Eyebrox » 15 Mar 2018, 2:48am

Cugel wrote:You'd be better to buy the full Shimano bleed kit.
Etc, etc

Cugel


What an excellent guide. A few unusual descriptive terms also help. The procedure is exactly as you describe, pushing the oil up to the lever then pushing it down to the caliper. I bought the funnel and stick from Halfords, a syringe from Boots, mineral oil from another bike shop (none in my Halfords) and the tubing from a pet shop (fish tank kit). It would have been easier just getting the lot at the one time.
I had to practise a few times but eventually I got the brakes working expertly. No manual or You Tube vid explains it quite as well as you have. Well done - a post that should be archived!!

Brucey
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Re: bleeding shimano brakes

Postby Brucey » 15 Mar 2018, 7:36am

there are quite a few techniques that (eventually) give you air-free brakes. There is certainly no one way of doing it.

However this isn't rocket science; air bubbles float upwards within the caliper body and if the caliper, hoses, MC etc are correctly oriented, simply pushing the pistons back forces the air out of the transfer ports, then up the hoses and out through the MC.

I have watched folks use syringes, hoses, pushing and pulling fluid in all directions and they have eventually succeeded. But I have also seen them take ages, wreck bleed fittings, have oil weeing out everywhere for no good reason, and have not succeeded. Note that unless the bleed nipple seals to the caliper body when a hose is connected to it (most don't), you are just as likely to suck air in at this point and make things worse, not better!

Remember that air in the caliper body is not easily displaced by pushing fluid up and down the hoses; the best way of shifting it is always to move the pistons in the caliper body.

I would say that at least 90% of the time you can bleed hydraulic brakes by simply having an additional reservoir at the MC (often this isn't even needed BTW), and using the MC and caliper to push fluid around the system. This cuts down on the risk of collateral damage, is quicker, and is usually more effective to boot.

If you are changing the fluid in a DOT4 system (a good idea as it deteriorates quickly) then it is not a bad idea to simply drain the fluid through the system from top to bottom. But again unless you work the caliper pistons, the fluid in the calipers won't be changed, and it is this fluid that is most important to change for fresh stuff.

There is a lot of nonsense spoken about bleeding brakes, and you would think it is some kind of magic, not basic plumbing, the way some folk carry on about it. IMHO if you are ever using a syringe connected to the system as a suction device, you are probably doing it wrong.

cheers
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Gattonero
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Re: bleeding shimano brakes

Postby Gattonero » 15 Mar 2018, 2:19pm

"modern" bikes tend to have more complicate hose routing. Well, one of the advantages of hydro is the ability of follow a cable path that a Bowden cable won't follow easily.
Especially is the hose routing that can play havoc when bleeding: on a road frame & bars there's many points where the hose goes up and down, and those are likely to become "air pockets" that will foul with your brake bleeding.

Sometimes you really have to remove the caliper and let it hang down, and move it if necessary. Also doing a two-way bleeding helps: first by gravity (from the funnel in the lever down to the caliper) then you do the other way by pushing with the syringe (from the caliper up to the funnel, to see the bubbles).
It also helps to keep the pistons not flush in the caliper but just so slightly extended, using a slightly filed down of the yellow spacers for that purpose.

After all is done, I prefer to keep the pistons slightly extended, fit the pads and fit the wheel, the caliper is aligned with the pads tight and to give the right spacing I use two pieces of rim-brake packaging: that thick transparent plastic seems to be the perfect shim!
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tykeboy2003
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Re: bleeding shimano brakes

Postby tykeboy2003 » 15 Mar 2018, 6:21pm

NUKe wrote:bleeding shimano brakes


What, no swear filter?

Cugel
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Re: bleeding shimano brakes

Postby Cugel » 26 Mar 2018, 1:17pm

Brucey wrote:there are quite a few techniques that (eventually) give you air-free brakes. There is certainly no one way of doing it.

There is a lot of nonsense spoken about bleeding brakes, and you would think it is some kind of magic, not basic plumbing, the way some folk carry on about it. IMHO if you are ever using a syringe connected to the system as a suction device, you are probably doing it wrong.

cheers


Please send me a vial of your perfection juice, as I too wish to be both infallible and certain at the mechanics, like yourself!

On the other hand, there is my experience of brake bleeding, which suggests the syringe is a necessary item as those dang air-bubbles seem disinclined to obey Brucey-law concerning the do's and don'ts of how they must behave,

But once the major bubbles are sucked (as well as squeezed) out, the tiny remaining recalcitrants will, it's true, eventually obey the more simplistic laws of physics, as riding-vibes shake them out of their naughtiness and they rise up a bit towards the brake lever end.

Cugel, who goes with the flow rather than the catechism and dogmas.

Brucey
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Re: bleeding shimano brakes

Postby Brucey » 26 Mar 2018, 5:10pm

you don't need 'perfection juice', you need 'common sense juice'.

Think about it; if you try 'to suck the air out' the best you will manage (because you won't make a perfect vacuum using a syringe) is to make the bubbles about 5 times bigger whilst the syringe is drawn back. You might be better off than when you started but using this technique you will always leave some air behind. If the bleed nipple is not sealed, or the systems seals are not very tight (they are not designed to seal against differential pressure in that direction) you will just draw air into the system.

Since there are other methods that work better, I use those instead.

cheers
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