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Shimano XTR Brake Bleed - first time. Suggestions?

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Shimano XTR Brake Bleed - first time. Suggestions?

Old 03-21-21, 03:58 PM
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klasse
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Shimano XTR Brake Bleed - first time. Suggestions?

So I decided to bleed my brakes! Previously, I figured that I would leave this job to the shop, but I had a change of heart after watching some YT videos. I found this one to be informative:

Brake lever level with the ground, whereas some rec 45 degree angle.
Anyone have a favorite bleed kit? I found one on ebay that's complete for $28. Looks like some places are charging nearly that much for the Shimano syringe - which seems excessive. I had no problem unscrewing the 2.5mm reservoir bolts on the lever.

The brakes are currently very squishy, almost no stopping power. Bike has not been ridden in a good 18 months, except for a spin last week.

If you have any tips to add, favorite kits, etc... please let me know, thanks!
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Old 03-21-21, 05:00 PM
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A threaded Leur lock for the syringe is ideal. You can use any disposable syringe. Just buy a few from your local heroin addict.

You may be able to get away with just topping off the fluid rather than bleeding it.

Use authentic Shimano mineral oil. Don't get any on the pads.
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Old 03-21-21, 06:18 PM
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klasse
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Originally Posted by wgscott View Post
A threaded Leur lock for the syringe is ideal. You can use any disposable syringe. Just buy a few from your local heroin addict.

You may be able to get away with just topping off the fluid rather than bleeding it.

Use authentic Shimano mineral oil. Don't get any on the pads.
Thanks, will remove pads and insert the brake block. I ordered a kit on ebay that has everything (except for leur lock) including Shimano mineral oil.
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Old 03-21-21, 07:06 PM
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You might want to try just burping the lever first. If it's been over a year since they were bled or they've never been bled do the full bleed. Fluid will probably come out grey/black so you'll know when you've purged it all. I ALWAYS finish w/ taking the syringe off/closing the bleeder screw and just pumping the lever w/ the cup attached. You'll get some small bubbles out that way. I also change the angle of the bike or rotate the lever a bit, that helps get any stubborn air out of the lever.
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Old 03-21-21, 08:30 PM
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Just know if you do screw up you can always do it again. Shimano brakes really aren't hard, even newer Sram aren't bad.
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Old 03-22-21, 01:25 PM
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klasse
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Originally Posted by cxwrench View Post
You might want to try just burping the lever first. If it's been over a year since they were bled or they've never been bled do the full bleed. Fluid will probably come out grey/black so you'll know when you've purged it all. I ALWAYS finish w/ taking the syringe off/closing the bleeder screw and just pumping the lever w/ the cup attached. You'll get some small bubbles out that way. I also change the angle of the bike or rotate the lever a bit, that helps get any stubborn air out of the lever.
Thanks, do you fill up the funnel with new brake fluid? Or just load up your syringe with fresh fluid, then push it into the system, removing the old fluid into the funnel? The video above is actually confusing me, because it's unclear to me where the old fluid is. This video from Bike Radar seems a lot more straightforward - he doesn't load the funnel with new fluid. Looks like all the old fluid is pushed into the plastic funnel (screwed into the lever) and that completes the job.

You keep the lever rotated (guessing around 45 degrees) throughout the process? I will employ your method of squeezing-pumping the lever with the funnel screwed in, the final step.

Here's the Bike Radar video:
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Old 03-22-21, 02:13 PM
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I'd give that video 3 out of 5 stars.
If you're going to 'bleed' then no fluid in the cup. Push fluid up from the caliper as he does. I rotate the lever so that the cup is flat when attached. This minimizes the chance of spilling. Push fluid up from the caliper. I tap the hose a few times while doing this as he does. Once you have some fluid in the cup it doesn't matter if you pull the lever. I push at least half a syringe of fluid up the line then close off the bleed screw. Remove the syringe and then you can burp the lever/master. I will change the angle of the bike in the stand a couple times while I'm doing this, or you can just rotate the lever back and forth. If I get more than a few small bubbles I'll strap the lever down tightly for 5-10mins and let the pressure do it's thing. This should give you fresh mineral oil all the way through the system and result in a very firm feeling lever.

Yes, the fresh fluid is pushing the old fluid into the cup. If you're just going to burp the lever always start with a little fluid in the cup, you won't be able to see the air bubbles come out if you don't.
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Old 03-22-21, 06:19 PM
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Originally Posted by klasse View Post
Thanks, do you fill up the funnel with new brake fluid?
There's two basic strategies for Shimano, top-down or bottom-up. The Park video is the bottom-up strategy. The official Shimano procedure is a top-down, which doesn't require the syringe, just something to catch the fluid on the bottom. For top-down, you fill the cup with fluid and let it drain through. For top-down, you must NEVER let the cup run out of fluid or you'll suck air in.

Bottom-up theoretically pushes air up to the lever on the top and out, making it easier to get a clean bleed. The challenge is that if you aren't super careful you can introduce an air bubble when you connect the syringe.
Top-down is a little simpler if you just want to quickly burp the brakes.

There are pages of internet wars debating these two strategies. Pick the one that seems the most reasonable to you.
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Old 03-22-21, 08:57 PM
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My favorite is the BKM-1 from Park Tool it feels nice in the hand and makes bleeding easy. The Park video on bleeding is pretty sufficient.
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Old 03-22-21, 09:52 PM
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Originally Posted by gsa103 View Post
There's two basic strategies for Shimano, top-down or bottom-up. The Park video is the bottom-up strategy. The official Shimano procedure is a top-down, which doesn't require the syringe, just something to catch the fluid on the bottom. For top-down, you fill the cup with fluid and let it drain through. For top-down, you must NEVER let the cup run out of fluid or you'll suck air in.

Bottom-up theoretically pushes air up to the lever on the top and out, making it easier to get a clean bleed. The challenge is that if you aren't super careful you can introduce an air bubble when you connect the syringe.
Top-down is a little simpler if you just want to quickly burp the brakes.

There are pages of internet wars debating these two strategies. Pick the one that seems the most reasonable to you.
No, Shimano shows both methods, starting w/ the caliper to lever, then lever to caliper, finishing w/ pumping the lever to force air out of the master/lever.
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Old 04-06-21, 02:58 PM
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Important to position the bleed valve at the lowest point? This is mentioned in some videos....supposedly it helps push all of the air out.

I bled my front brake, don't think I did an A job, more like a C or D.
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Old 04-06-21, 03:15 PM
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Yes, the bleed valve/caliper should be as low as possible even it means removing it from the frame. Lever obviously at the highest point, rotated to a horizontal position. If you did that poorly you should do it again til it's solid.
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