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  1. #1
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    New Shimano M785 Brake Bleed Question

    Hi guys, I've searched through threads and downloaded instructions but after a couple hours of trying to bleed me new Shimano XT brakes (shortened lines after installing) and having trouble getting all the air out of the system.

    I installed the front brake and shortened the without any problem but that was after I read about the trick of pumping the lever a few times without the pads installed to push the pistons out. That went smoothly, shortened the line without getting any air in the system.

    However, the rear brake has not been so easy for me. I've spent too much time fighting with getting air out of the line. I've followed the Shimano instructions but as yet have been unsuccessful.

    In general, here is what I've done without too many specifics:

    1) Filled a syringe and attached it to the lever bleed port.
    2) Filled another syringe and attached it to the rear caliper bleed port.
    3) Pushed fluid from the caliper to the lever.
    4) Removed the syringe from the rear caliper and replaced it with a plastic bag (bleed tube into bag).
    5) Opened the caliper bleed port and let fluid drain from the lever, using the syringe at the lever as an extended reservoir to allow extra fluid to drain through to the caliper.
    6) Watched air bubbles come out of the caliper and bled fluid through until I saw no more bubbles.
    7) Closed the caliper bleed port. Also opened/closed the caliper bleed port a couple time as per the instructions.
    8) Wiggled the lever and tried to get bubbles out of the reservoir.

    I've done this a couple times and have not been able to get the lever to stiffen up. I think I have the general idea but I must be doing something wrong.

    Shouldn't I just need a funnel attached to the lever bleed port, a bleed hose, and a plastic bag to do the job?

    Suggestions?

  2. #2
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    From what I've seen, Shimano's current brakes do not like being bled from the top down, I had a heck of a time trying to bleed a Saint when I didn't have the proper tools. I only had one syringe and no funnel so I was putting in fluid from the top and letting it run through a tube into a plastic bag from the caliper end. Same thing with a Deore brake, it wasn't fun. I eventually got there but I had to pull out everything in my bag of tricks from when I was a bike mechanic.

    If you have the funnel, push the fluid in from the caliper end until bubbles stop coming out from the top, squeeze & tap the lever a few times while you're pushing the fluid through. Close off the caliper bleed port, unscrew the funnel, and you're done.

    If you're using 2 syringes, push the oil up & down a couple times to clear out all the bubbles, tap & squeeze the lever a few times while you're doing it, then finish by pushing fluid up from the caliper end. Close the caliper bleed port, remove the syringes, and you should be good.

  3. #3
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    Thanks Aerius, it should be about that simple but for some reason I have been unable to get it to work. I will try again with pushing the fluid up to the lever. I know air bubbles always rise.

  4. #4
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    After working with the brakes a bit more I was able to get 98% of the air out of the system, the lever feels very good although not quite as good as the front brake. I've read a few other similar threads in this forum which helped me understand the process a bit better.

    I may take one more crack at them to see if I can get that last 2% out to make the lever feel perfect but for now I've got it possibly good enough.

  5. #5
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    Epic for the brakes you have m-785 it is almost impossible to do without the funnel.

    http://www.google.ca/imgres?imgurl=h...QEwBA&dur=1928

    attach your syringe to the bottom and push fluid out. The front will always feel stronger as the brake line is shorter. it is not much of a difference but as your comparison goes 98% of the front sounds about right to me. Make sure you clean all the brake fluid up from both the caliper and the lever to avoid contamination of your pads. had that happen to me and it is horrible riding with no brakes and a squel that sounds like a freight train. Hopefully that helps you

  6. #6
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    Quote Originally Posted by aerius View Post
    If you have the funnel, push the fluid in from the caliper end until bubbles stop coming out from the top, squeeze & tap the lever a few times while you're pushing the fluid through. Close off the caliper bleed port, unscrew the funnel, and you're done.
    Watching this thread because after about a year of riding it's probably time to bleed my M785 brakes.

    Interesting that the preferred bleeding method in practice appears to deviate from the Shimano suggested method.
    http://bike.shimano.com/media/techdo...9830746864.pdf
    Sounds like the preferred method is to leave out Step 4 and not use the baggie after the syringe pushes the fluid from the caliper into the funnel.

  7. #7
    El CicloPath!!!!!!!
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    are you using the yellow bleed block? One of the crucial steps to getting firmness is that the pistons are properly spaced. There is a step in which you squeeze the level, after you have bled the brake and gotten the air out of the caliper and lever. At this stage, the lever should firm up after a few hard and sustained pulls. This is with the yellow bleed block or something of proper width in place. Then, with the lever squeezed and sustained, you open and close the caliper port to to get more air out.

  8. #8
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    Where can you buy threaded syringes that will fit Xt brakes

  9. #9
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    Quote Originally Posted by bigdog100 View Post
    Where can you buy threaded syringes that will fit Xt brakes
    No need to look for threaded syringes. I just screwed in the regular syringe and self threaded it into the hole. Btw, I had a similar experience where the rear felt softer than the front no matter how I blead it until I swapped the rear pads to the front. Go figure...

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