Tech Q&A

Fix/Workaround: Shimano XT M785 Brake Lever

Sidmouth's Photo Sidmouth 06 Dec 2015

I honestly think SLX and XT brakes are identical, its not worth re jigging a production-line, for something so similar, I opened the XT and XTR brakes they are basically identical

, except for the free stroke mechanism,

Skylark's Photo Skylark 06 Dec 2015

I honestly think SLX and XT brakes are identical, its not worth re jigging a production-line, for something so similar, I opened the XT and XTR brakes they are basically identical
, except for the free stroke mechanism,

All virtually identical internals apparently from Deore 615 and up, just have slightly different levers/external adjustments. Only one that may be unique is the Xtrs.

Sidmouth's Photo Sidmouth 07 Dec 2015

here are the photos of the XTR, except for this pin, looks simile enough, just tap the pin out, i seriously tried, it did not even budge

Attached Images

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HowardSteele's Photo HowardSteele 07 Dec 2015

I honestly think SLX and XT brakes are identical, its not worth re jigging a production-line, for something so similar, I opened the XT and XTR brakes they are basically identical

, except for the free stroke mechanism,

When my xt levers packed up i just bought 2 Slx levers and switched the covers so the slx body doesn't have the free stroke adjust...that doesn't work on the XT  anyway...the SLX lever adjustment knobs are slightly different but not enough for anyone to notice .

PS.  I had the XT..I spec b mounted with shifters...The SLX uses the floating bolt mount so you have to have or acquire the different mounting bolts.


Edited by howardsteele, 07 December 2015 - 09:41 .

droo's Photo droo 07 Dec 2015

here are the photos of the XTR, except for this pin, looks simile enough, just tap the pin out, i seriously tried, it did not even budge

 

I'm willing to bet there's a grub screw holding that pin in place somewhere, you've just got to find it...

Meezo's Photo Meezo 07 Dec 2015

cool image... you can see what the piston and spring actually does

 

 

Attached Images

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Sidmouth's Photo Sidmouth 07 Dec 2015

 

I'm willing to bet there's a grub screw holding that pin in place somewhere, you've just got to find it...

I seriously looked, its a tiny pin, no thread, i used the smallest punch that fitted, but that needle would not move.thereis no screw port even close.

but will look again

That needle is also the hinge for the free stroke flap, 

Lance Roberts's Photo Lance Roberts 11 Dec 2015

First off I must stress that I am by no means a qualified bicycle mechanic, I do have little very little experience with them. Secondly I cannot take full credit for this fix, the idea was given to me by a very very generous hubber who’d had offered to fix for me for free. KUDOS @BikeWhisperer and a close friend @gyro for the time

Ok, then this is not an avid or shimano appreciation thread, nor an avid vs shimano thread.

SYMTOMPS:

Pull lever, and it does not return at all or very slow and spongy.

If bike in open sun, levers lock up.

 

POSSIBLE CAUSES:

Dirt and grime build up in the lever cylinder, as well as on the piston. See below

With the dirt and grime build up, when in heat the swelling cause the lockup and no return of lever.

TOOLS NEEDED:

2mm Allen Key

Star Screwdriver

Isopropyl Alcohol

Toilet roll/Roller towel

Thin Nose Pliers

1 x 3000 grit Sand Paper

1 x 2000 grit Sand Paper

1 x 1000 grit Sand Paper

 

This is from the shimano site, I will make reference to the number here in my photos as well

 

For starters is always good to remove the lever completely off the brake line.

Below is an image of a lever I had repaired and one that was going to get repaired, taken as is off the brake system

 

Remove 8 in diagram above like below, there a tricky little rubber cover than can be removed with a thin small screwdriver or pin

 

 

Push out 5 using the 2 allen key, this will separate the lever trigger from the rest of the lever

 

 

Use the thin nose pliers to twist and remove the roller connector/part of the lever

 

Using the star screwdriver, remove 6

 

Turn the lever upside down ie. reservoir facing down and use the screw driver to pop out the plastic roller fitting

 

..and finally we get to the problem child, this is just to show you how the piston is actually stuck in the cylinder

 

Easiest way to remove the piston and spring is using the 2mm allen key

 

 

This is your best friend keep on using it throughout the process, clean up all you bits you can, all the none plastic and rubber bits I let sit in the isopropyl alcohol for a few mins

 

…so time for the fix the red blocks is whats needed to be sanded down using the 3000 then to 2000 then smoothen with the 1000, very very lightly and depending on your piston condition very very little too.

 

 

 

PS: it may or may not be easier to remove the rubber seals, just be very careful when sanding around them

 

 

what I do to test I push the spring in with the piston, and see if there’s a “spring” back in the piston by pushing in and out the cylinder

 

And the final product!

 

 

 

 

DISCLAIMER:

I am not in any way affiliated to Shimano. I will not take any responsibility for any damage done to your lever or other parts when attempting this fix. I am not 100% sure of the repercussion sanding down the old dirt or grime build up, and will not be held responsible if it does fail.

 

Our scholars tell us, that we have to go out to seek knowledge and whatever knowledge is learnt must be shared so it be beneficial for myself but humanity at large…

 

Just a quick question.

I just realised that my rear brake is doing the exact same thing as explained above. 

 

I have a race on Sunday and don't want to take a chance by following these steps for the first time and not being able to fix the problem so close to the ride.

 

If I leave it like this for now do I run the risk of not having brakes during the ride?

Meezo's Photo Meezo 11 Dec 2015

Just a quick question.

I just realised that my rear brake is doing the exact same thing as explained above. 

 

I have a race on Sunday and don't want to take a chance by following these steps for the first time and not being able to fix the problem so close to the ride.

 

If I leave it like this for now do I run the risk of not having brakes during the ride?

 

probably not, however what i have found that in extreme heat the piston would swell and the "brakes" would lock up due to the piston not being able to return the lever completely. if the race is on Sunday you could easily do this fix, but if you not keen on risking it, ride as is

Bobbo_SA's Photo Bobbo_SA 11 Dec 2015

probably not, however what i have found that in extreme heat the piston would swell and the "brakes" would lock up due to the piston not being able to return the lever completely. if the race is on Sunday you could easily do this fix, but if you not keen on risking it, ride as is

 

What happens though is not that you don't have brakes, but that your brake wont release so you will be riding against your brake most of the way

Lance Roberts's Photo Lance Roberts 11 Dec 2015

probably not, however what i have found that in extreme heat the piston would swell and the "brakes" would lock up due to the piston not being able to return the lever completely. if the race is on Sunday you could easily do this fix, but if you not keen on risking it, ride as is

 

I'll look over the steps again and see if I'll take a chance tomorrow, don't really feel like riding 40 kms against the brake... And it'll wear the brakes down all the way, I'm sure.

 

Bleeding the brake is fine, but would I be able to do it without removing the hose? That will save some time.

karlito's Photo karlito 19 Jan 2016

You Sir are a true champion of the people!

 

I am having the exact same problem, and phoned two bike shops already.

 

The one says I damaged the seals because I used a syringe and will most likely have to replace, the other says that they will have to send it in to Shimano as they cannot do anything to the level as it is a "sealed unit"

 

I would think that with the amount of people riding with XT this would be a well know procedure??

 

Will try this out and report back.

Meezo's Photo Meezo 21 Jan 2016

You Sir are a true champion of the people!

 

I am having the exact same problem, and phoned two bike shops already.

 

The one says I damaged the seals because I used a syringe and will most likely have to replace, the other says that they will have to send it in to Shimano as they cannot do anything to the level as it is a "sealed unit"

 

I would think that with the amount of people riding with XT this would be a well know procedure??

 

Will try this out and report back.

 

any luck yet, i see there a hubber having an issue with XTR

Mopkop's Photo Mopkop 27 Apr 2016

Hi guys

 

Ive got a huge problem. Im running a set of XT 785 brakes. I am always having to bleed the rear brake, on a monthly basis if I'm using the bike alot.

 

My method would be to open the bleed screw on the lever to check if I could see any fluid. Its always dry. I then screw on the bleed funnel, add some oil and then pump the level while I tap the brake hose. This gets most/all the bubbles out but the brake still feels spongy.

 

Last week I noticed that the hose is wet. I replaced the olive and then tightened up the hose another 1.5 turns from where it was before I replaced the olive. Its all dry now BUT I've got absolutely no braking power!

 

Ive bled the brake on my usual method, NOTHING

 

Ive bled using gravity, top to bottom, NOTHING

 

Ive opened up the lever to check that the bladder, which is under section 4 of the diagram, has not collapsed, its all good.

 

Ive tried bleeding bottom to top using a syringe with very little force, NOTHING.

 

The lever now is wet, section 7 and 8 on the diagram. I have got 2 XT levers that ive stripped and butchered previously as about 1.5 years ago I also sat with no power and the LBS recommended I replace the lever. Ive used the donor lever for its bladder as the previous bladder was torn.

 

HELP!!!

 

Mopkop

PeterF's Photo PeterF 27 Apr 2016

 

I seriously looked, its a tiny pin, no thread, i used the smallest punch that fitted, but that needle would not move.thereis no screw port even close.

but will look again

That needle is also the hinge for the free stroke flap, 

Check Meezo's diagram, number 8 shows the location of the grub screw and the little rubber grommet hiding it, for the XT brakes.  I'm pretty sure that the XTR's should be the same.

Skylark's Photo Skylark 28 Apr 2016

Hi guys

Ive got a huge problem. Im running a set of XT 785 brakes. I am always having to bleed the rear brake, on a monthly basis if I'm using the bike alot.

My method would be to open the bleed screw on the lever to check if I could see any fluid. Its always dry. I then screw on the bleed funnel, add some oil and then pump the level while I tap the brake hose. This gets most/all the bubbles out but the brake still feels spongy.

Last week I noticed that the hose is wet. I replaced the olive and then tightened up the hose another 1.5 turns from where it was before I replaced the olive. Its all dry now BUT I've got absolutely no braking power!

Ive bled the brake on my usual method, NOTHING

Ive bled using gravity, top to bottom, NOTHING

Ive opened up the lever to check that the bladder, which is under section 4 of the diagram, has not collapsed, its all good.

Ive tried bleeding bottom to top using a syringe with very little force, NOTHING.

The lever now is wet, section 7 and 8 on the diagram. I have got 2 XT levers that ive stripped and butchered previously as about 1.5 years ago I also sat with no power and the LBS recommended I replace the lever. Ive used the donor lever for its bladder as the previous bladder was torn.

HELP!!!

Mopkop

When the master cylinder was going dry, ie no fluid, where was the fluid going?

Hydraulic brakes are sealed systems, so the they must have had a pretty dik leak somewhere and that must have shown itself as a pretty noticeable oil leak.