Shimano R8070 Hydraulic Disc Problems
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  1. #1
    TheKing
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    Shimano R8070 Hydraulic Disc Problems

    I had a road bike built this spring with Shimano R8070 disc brakes. Since day one I have not been impressed with the performance of these brakes. The travel on the brake levers is huge. At full brake I have less than an inch of distance between the lever and handlebars. The rear brake has failed twice to the point where at full brake it could not stop the wheel. I had it back to the shop twice at which time they did a brake bleed and said it was probably air in the system. It would work fine for a few weeks and then braking performance would deteriorate. There are no signs of fluid leakage. Recently the front brake has started to fail similar to the back. If I pump the levers several times it seems to bring back sufficient braking to do a ride. I do hang the bike by the wheels, but I also do the same with my gravel bike equipped with SRAM disc which works perfectly and has far greater breaking capacity. I am at a loss as to what to do next. I wanted to contact Shimano to inform them of this issue, but could not find a contact method. They show no R8070 recall notices on their website. Any ideas would be appreciated.
    Last edited by TheKing; 10-15-2019 at 03:14 AM.

  2. #2
    RoadBikeReview Member
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    Definitely sounds like you have air in the system, those brakes are very strong, they should bring you to a stop quickly (as long as you're not compressing air that is). You should check line fittings and bleed/reservoir screws and bleed both again, even a little air in the system will decrease performance, the fact that you hang the bike from the wheels should make no difference.
    Let us know what you find and good luck.
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  3. #3
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    Quote Originally Posted by upstateSC-rider View Post
    the fact that you hang the bike from the wheels should make no difference.
    Only in a perfect world, if there are some issues, hanging could definitely cause those problems to present themselves.
    BANNED

  4. #4
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    From Shimano dealer service manual:

    "This disc brake system is not designed to be turned upside down. If the bicycle is turned upside down or on its side, the air bubbles inside the reservoir tank may move in the direction of the calipers."

    Sounds like the problem IS with how you're storing the bike.

  5. #5
    'brifter' is a lame word.
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    OP: Sounds like your shop doesn't know how to bleed Shimano brakes.

    Brakes.

    Not breaks.
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  6. #6
    Cleavage Of The Tetons
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    Spelling is his Achilles’ heal.

  7. #7
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    Quote Originally Posted by nova_rider View Post
    From Shimano dealer service manual:

    "This disc brake system is not designed to be turned upside down. If the bicycle is turned upside down or on its side, the air bubbles inside the reservoir tank may move in the direction of the calipers."

    Sounds like the problem IS with how you're storing the bike.
    I stand corrected.
    Have the brakes re-bled and store the bike rubber-side down and see if it helps.
    Good luck
    In reference to the Assault on Mt Mitchell...
    Quote Originally Posted by merckx56
    The easier solution is to find a biker bar in Spartanburg the night before, go in and pick a fight. The ass-whipping you'll get will be far less painful than the one Mitchell will give you the next day!

  8. #8
    'brifter' is a lame word.
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    Quote Originally Posted by rideit View Post
    Spelling is his Achilles’ heal.
    I sea what you did there.
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  9. #9
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    Quote Originally Posted by nova_rider View Post
    From Shimano dealer service manual:

    "This disc brake system is not designed to be turned upside down. If the bicycle is turned upside down or on its side, the air bubbles inside the reservoir tank may move in the direction of the calipers."

    Sounds like the problem IS with how you're storing the bike.
    I'm surprised this is still an issue after over 2 decades of disc refinement in the mtb world. So no flipping the bike over when changing a flat then? I think you can flip the bike over, just don't flip it over while pressing the brake lever because that will definitely pump air into it if the reservoir is not full.

  10. #10
    'brifter' is a lame word.
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    Quote Originally Posted by aclinjury View Post
    I'm surprised this is still an issue after over 2 decades of disc refinement in the mtb world. So no flipping the bike over when changing a flat then? I think you can flip the bike over, just don't flip it over while pressing the brake lever because that will definitely pump air into it if the reservoir is not full.
    You should never flip a bike upside to remove/install a wheel anyway...doesn't matter what kind of brakes you have.
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  11. #11
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    Quote Originally Posted by cxwrench View Post
    You should never flip a bike upside to remove/install a wheel anyway...doesn't matter what kind of brakes you have.
    This truth is going to hurt some people.

  12. #12
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    Quote Originally Posted by aclinjury View Post
    I'm surprised this is still an issue after over 2 decades of disc refinement in the mtb world. So no flipping the bike over when changing a flat then? I think you can flip the bike over, just don't flip it over while pressing the brake lever because that will definitely pump air into it if the reservoir is not full.
    Since most hydraulic brake systems are not hermetically sealed, there will always be some air in the reservoir and no amount of refinement will fix that. If the bike is flipped only for short period, such as changing a flat, the small amount of air won't have traveled too far up the system. However, if left upside down for an extended period, the air WILL travel to the highest point in the system, which is likely the caliper.

  13. #13
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    Quote Originally Posted by cxwrench View Post
    You should never flip a bike upside to remove/install a wheel anyway...doesn't matter what kind of brakes you have.
    That is so embarrassing for the bike!
    BANNED

  14. #14
    TheKing
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    Quote Originally Posted by aclinjury View Post
    I'm surprised this is still an issue after over 2 decades of disc refinement in the mtb world. So no flipping the bike over when changing a flat then? I think you can flip the bike over, just don't flip it over while pressing the brake lever because that will definitely pump air into it if the reservoir is not full.
    This summarizes my thoughts on this issue. I have a hard time accepting I can't hang my road bike upside down next to my other bikes with hydraulic brakes or lay it down in my car. Apparently this bike does have some air in the system that moves to the caliper when inverted. I believe that having a reservoir fully filled can avoid this problem. I will do a thorough bleed and finish with a full reservoir and then hang the bike up and see what happens.

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