XT M8000 Bleed Issue

moorey said:
If you get even the slightest amount of oil on the caliper, it’s a thorough clean either way. Also, business cards are super waxy. Use inside out cereal box cardboard, amateur.
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I give up...you win, yoor the best!
OP, just get Moorsy to come around and do it, any other way will most likely be wrong
 
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moorey said:
During bled...Lever all the way out, servo wave all way in? (Reset reach, and screw out servo wave after finishing)
After removing funnel and replacing reservoir screw, apply a bit of pressure on syringe at caliper end and close off bleed nipple with pressure still being applied.
Click to expand...
Winning.

That bit of pressure with the reservoir screw in was the ticket. Has a slight amount of pressure at the lever afterwards, and when I reinstalled the funnel a stack of air came out and she bled like normal. Lever is hard as now.

Thanks mate (and everyone else for input).

Now I don't think there's enough isopropyl in the world to clean this mess up but at least I can get on with building this thing now.
 
ashes_mtb said:
Winning.

That bit of pressure with the reservoir screw in was the ticket. Has a slight amount of pressure at the lever afterwards, and when I reinstalled the funnel a stack of air came out and she bled like normal. Lever is hard as now.

Thanks mate (and everyone else for input).

Now I don't think there's enough isopropyl in the world to clean this mess up but at least I can get on with building this thing now.
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You do end up with a bees dick of positive pressure in there, so always have your syringe on the caliper bleed nipple and release any pressure back into there during next bleed, rather than removing funnel port first. If not already doing so, after funnel is on, suck a little oil back into syringe to remove air from bleed nipple before pushing oil back up. Sounds like the bleeding obvious...pun intended...but many people seem not to, and immediately push a little air straight into the caliper.
 
ashes_mtb said:
Had to install a new hose for my rear XT brake and am having a hell of a time getting them going. Still getting no lever feel or movement at the piston.

Barb and olive are in good and no leaks.

Ditto at the banjo, remembered the o-rings and there's no leaks there.

Have pushed oil up from bottom to top with a syringe about 6 times. Oil comes up into the funnel with no air bubbles.

Also tried just a gravity bleed from the funnel down. Both with just gravity and also pumping the lever.

No air bubbles coming out in the funnel when I pump the levers with bottom bleed point shut.

Got me beat - any suggestions?
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Hey man another idea that might help, the pistons may be seized up a bit. Try using something like Isopropyl alcohol or brake cleaner with one of those long thin hose attachments to get it right into the space around the pistons. Then use a cotton bud with a small amount of brake fluid and run it around the piston. Capillary action will suck it in and should help un-seize the pistons. Then I'd give it another good clean with isopropyl alcohol before putting the pads back in. I've found this has loosened pistons on my XT M8000's and made them a lot more consistent.
 
EsPeGe said:
Then use a cotton bud with a small amount of brake fluid and run it around the piston. Capillary action will suck it in and should help un-seize the pistons.
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Just an extra detail on this point, make sure the fluid used for piston lubrication is the same as what the brake is filled with. If it's a mineral oil system, Shimano, Magura, Tektro/TRP etc, use mineral oil, preferably the correct blend for the specific brake brand; if it's a DOT system - SRAM, Hope, Formula etc, use DOT fluid to lube the pistons.
 
moorey said:
During bled...Lever all the way out, servo wave all way in? (Reset reach, and screw out servo wave after finishing)
Click to expand...
ServoWave is a linkage between the lever and master piston pushrod; it's not independently adjustable, but does adjust a bit as
a side effect of stroke adjustment. Reach adjust moves only the lever and has no effect on any other part of the system.

When bleeding, fully retract the stroke adjust screw to maximise master cylinder volume (the adjust screw works by advancing the master piston down the bore; it is subtle, but not quite as ineffective as some critics would have you believe). Pulling a bit of vacuum pressure with the bleed syringe will help suck air out that might otherwise just be pushed into corners; a combination of positive and vacuum pressure is essential if the caliper is dry, because that's the most convoluted plumbing & most likely to trap air. Bleed the brake with both upward and downward oil flow, positive and negative pressure from both syringe and lever. Close the caliper port, refit the pads & wheel, and with the cup still connected and open (basically an extension reservoir), pump the brake to set pad clearance.and fill the plumbing. Remove cup & fit the reservoir plug. Adjust stroke screw to set the brake feel, then set the reach.
 
I can’t tell if you’re agreeing, disagreeing or elaborating....
Either way, after many hundreds of bleeds I’ve worked out the most reliable method for me that gives me the best lever feel....even if I don’t explain it well or properly.
 
moorey said:
During bled...Lever all the way out, servo wave all way in? (Reset reach, and screw out servo wave after finishing)
After removing funnel and replacing reservoir screw, apply a bit of pressure on syringe at caliper end and close off bleed nipple with pressure still being applied.
Click to expand...
Hey @moorey have you done this trick to any of the 11 speed or 12 speed Shimano 4 pot brakes. I seem to recall you got some of the m7120 brakes from Bikebug when they were cheap. Did you manage to get rid of the wandering bite point?

Sent from my SM-G970F using Tapatalk
 
Oddjob said:
Hey @moorey have you done this trick to any of the 11 speed or 12 speed Shimano 4 pot brakes. I seem to recall you got some of the m7120 brakes from Bikebug when they were cheap. Did you manage to get rid of the wandering bite point?

Sent from my SM-G970F using Tapatalk
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Brakes have a speed now?
No late model 4 pot here. Just Saint on Felix's operator, and m8000/zee on his Process sorry.
Only know 2 people with XT 4pot, and they haven’t mentioned the issue.
@Shredden Mentioned/ordered the cheap SLX off there....but wasn’t that a fuckup with listing and no stock?
 
I bought the cheap 7120 calipers from bikebug, I am running 9100 levers though. Haven't ridden them though.
Running a few sets of 9120s, one gave me trouble getting a good bleed. Had to replace, olive/barb and also the threaded watsy me call it that screws to the leaves. Wasn't sealing properly at the lever and would wander. After this they have all been perfect.
Running 9100 levers on m8000 calipers on comuter. These have run perfectly, done a lot of kms. Last bleed oil was black.
 
Yeah I didn't end up getting them in the end, some others did though.

I got XT M8120s complete from AliExpress. From memory just under $400? Can find a link if anyone wants.
 
Oddjob said:
Hey @moorey have you done this trick to any of the 11 speed or 12 speed Shimano 4 pot brakes. I seem to recall you got some of the m7120 brakes from Bikebug when they were cheap. Did you manage to get rid of the wandering bite point?

Sent from my SM-G970F using Tapatalk
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The problem is not in the callipers. I had one M8000 2 piston set wander badly, when I stuck a M8020 calliper on, it reduced the problem, but I didn't follow the whole bleed process. 12 months later, I did the whole step by step process and all but eliminated the wandering. It's an eighth of a turn on the reach adjuster, and temperature related. The rear lever has never changed.
 
Cardy George said:
The problem is not in the callipers. I had one M8000 2 piston set wander badly, when I stuck a M8020 calliper on, it reduced the problem, but I didn't follow the whole bleed process. 12 months later, I did the whole step by step process and all but eliminated the wandering. It's an eighth of a turn on the reach adjuster, and temperature related. The rear lever has never changed.
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I would agree that it is the lever not the caliper.
Also definitely heat related from when lever wandered (After long decent). I never felt this with 785s and always bled the same.
The set I had trouble with, really was doing my head in. Didn't matter how I bled them eventually it came back. The olive wasnt sealing evenly at the lever.
The dual contact point is a nice feature on the new levers if you are looking for an excuse to change.
 
On the XTR 9000 / 9100's its all to do with the bleed. I swapped levers (from M9000 to M9100) based on some internet BS reports that the redesigned lever/master cylinder would cure the variable bit point. It did not. Then I took extra, extra care with the bleed and that fixed the issue. I should have known better than to take someone else's word for it.
 
I'd only had the bite point issue once until fairly recently, and that time just bleeding it quickly fixed it.

Recently though, I swapped the levers on my shigura brakes and found I was getting the bite point issue. Bled them again and still had the same thing

Then I remembered a little trick from way back about "bleeding up" the brakes. Basically I opened the reservoir port, and squeezed the lever a bunch of times. Eventually I started seeing bubbles rise to the bleed port, so I dribbled a bit of hydraulic fluid back in and repeated. Eventually you stop see bubbles and the wandering bite point is gone.

I've since done this on other brakes too and improved the lever feel, they didn't have a wandering bite point, but some were definitely less solid a feel than others.

Sent from my G8441 using Tapatalk
 
SummitFever said:
On the XTR 9000 / 9100's its all to do with the bleed. I swapped levers (from M9000 to M9100) based on some internet BS reports that the redesigned lever/master cylinder would cure the variable bit point. It did not. Then I took extra, extra care with the bleed and that fixed the issue. I should have known better than to take someone else's word for it.
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BS internet no if it's on there it's gospel.

I think there are a lot of variable to this one. No 2 cases are the same.
My assumption was it was coming from the lever. ASSumptions can make an arse of yourself.
My theory was that once brakes got hot, the wandering bite point came back. I'd bled them many times with the same outcome. Worked fine till they got real hot then away again. A lever bleed always fixed this for a while and always got air out (quick flicks). This was m8000 and also a troublesome 9120. The 9120 was eventually fixed with new barb olive and connector. I've fitted 9100 levers to m8000 calipers, quick bleed and been faultless.
If I was to ride 70ks with say 300m elevation I wouldn't have a problem with wandering lever.
If I rode 25ks with 1300m elevation it was there.
My ASSumption when hot it was putting more pressure at the lever and air was getting in.
All my brakes with newer lever once bled properly have worked perfectly. More time spent doing a thorough lever bleed helps in my opinion.
 
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