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Thread: Does using a hydraulic brake while bike is upside down cause it to lose pressure?

  1. #1
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    Default Does using a hydraulic brake while bike is upside down cause it to lose pressure?

    This morning I got a flat on the way to work. I have hydraulic disc brakes. I do not touch the brakes while the wheel is out. Today, I had flipped the bike over to remove the rear wheel and kept it that way until I had the wheel seated again (more than half an hour - that tire was a BEAR to get back on the wheel!). I had the tire in, rotated the crank to make sure I had the gears aligned, let it spin a while and then used the brake to check that. All good. I flipped the bike back over. Put all my stuff on it and rode off. I needed the brake and it was all mush. By the time I got to work it was stronger. One previous occasion I did not have this issue, but I didn't flip the bike until trying to get the wheel back in (I just couldn't do it upright) so it was upside down for a short time. Another occasion, when the bike was flipped the whole time this did happened and I brought it to shop and we ended up putting a new brake on. Is the loss of pressure expected? Should my brake now be fine, or was the loss of pressure a sign I need to get it fixed, again?

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    A whole new brake? Sounds like your shop doesn't know much about hydraulic brakes.

    Yes, this happens to me whenever i change the rear pads on the longtail. It's really tough to do without flipping the bike because it's so big and heavy. I usually just pump the brake for a minute or two to work the bubbles out and it's fine. At most I'd expect you'd have to bleed the lines. Replacing the brake seems pretty extreme.

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    Quote Originally Posted by jrenaut View Post
    A whole new brake? Sounds like your shop doesn't know much about hydraulic brakes.

    Yes, this happens to me whenever i change the rear pads on the longtail. It's really tough to do without flipping the bike because it's so big and heavy. I usually just pump the brake for a minute or two to work the bubbles out and it's fine. At most I'd expect you'd have to bleed the lines. Replacing the brake seems pretty extreme.
    Yeah - worst case, if one of the seals wasn't the greatest, inverting the bike could lead to a small loss of fluid as well as the air bubbles moving around, but even then: it'd be a brake bleed rather than replacing the brake itself.

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    No. Hydraulic brakes should work in any orientation. Sounds like you have a leak somewhere (o-ring, seals, screws, pinhole in the line, etc.) and air got into the system. Did the shop tell you what the problem was? What exactly did they replace?

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    Quote Originally Posted by ImaCynic View Post
    No. Hydraulic brakes should work in any orientation. Sounds like you have a leak somewhere (o-ring, seals, screws, pinhole in the line, etc.) and air got into the system. Did the shop tell you what the problem was? What exactly did they replace?
    ehhh Shimano's dealer manuals appear to disagree with you. I think they know air getting into the brakes is a regular issue.

    https://si.shimano.com/pdfs/dm/DM-BR0008-08-ENG.pdf

    • The disc brake is not designed to work when the bicycle is upside down. If the bicycle is turned upside down or on its side, the brake may not work
    correctly, and a serious accident could occur. Before riding the bicycle, be sure to operate the brake lever a few times to check that the brakes operate
    normally. If the brakes do not operate normally, stop using the brakes and consult a dealer or an agency

    • When turning the bicycle upside down or on its side, the brake system may have some air bubbles inside the reservoir tank which are still there when
    the bleed screw is closed, or which accumulate in various parts of the brake system when it is used for long periods. This disc brake system is not
    designed to work with the bicycle 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. If the bicycle has been turned upside down or on its side, be sure to operate the brake lever a few times to check that
    the brakes operate normally before riding the bicycle. If the brakes do not operate normally, adjust them according to the following procedure.
    Last edited by Emm; 04-12-2019 at 12:37 PM.

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    Quote Originally Posted by Emm View Post
    ehhh Shimano's dealer manuals appears to disagree with you. I think they know air getting into the brake is a regular issue.

    https://si.shimano.com/pdfs/dm/DM-BR0008-08-ENG.pdf

    • The disc brake is not designed to work when the bicycle is upside down. If the bicycle is turned upside down or on its side, the brake may not work
    correctly, and a serious accident could occur. Before riding the bicycle, be sure to operate the brake lever a few times to check that the brakes operate
    normally. If the brakes do not operate normally, stop using the brakes and consult a dealer or an agency

    • When turning the bicycle upside down or on its side, the brake system may have some air bubbles inside the reservoir tank which are still there when
    the bleed screw is closed, or which accumulate in various parts of the brake system when it is used for long periods. This disc brake system is not
    designed to work with the bicycle 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. If the bicycle has been turned upside down or on its side, be sure to operate the brake lever a few times to check that
    the brakes operate normally before riding the bicycle. If the brakes do not operate normally, adjust them according to the following procedure.
    Ok, I am surprise to see that Shimano system does not have a way to prevent this behavior. I use TRP HY/RD calipers and do not recall seeing anything about not turning the bike upside down. I do so on regular basis and have not experienced this issue.

    If this is normal behavior, then I really like to hear why the shop replaced the brake.

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    I discovered this phenomenon many years ago on Avid hydraulic mountain bike brakes when squeezing the lever as the bike was vertical (front wheel in air and rear on ground) rolling it down the stairs into my basement. Later I found the same behavior on Shimano brakes. All you have to do is pump the brakes quickly when righting the bike and it self-corrects. Maybe I'm missing something, but it's cray cray that they replaced your whole brake. The most they should've done was bled it.

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    Thank you all. Sounds like I should not have been surprised by it and the fact that it got better with time is appropriate. I will look into the correct procedure for my brakes when righting them and line bleeding.

    I think the replacement was also because the brake had been soft for a while, which I mentioned at that time, thus likely a leak somewhere, and I am not sure that they understood that I had not used the brake with the wheel out ("So how did you get it open?" was one question I got, to which I answered that I never used the brake without the wheel in place, but he still seemed confused). Also, since it was still on their protection plan it was far easier to replace it. Now, they should have known that it was normal and told me because I did ask about that at the time. Some of the mechanics there are really good, but know many are in training (one told me so in the past).

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    At least with Shimano, the brake bleed kit is something most people should be able to use successfully. The process is a little weird - it helps to have a friend who's done it - but it's not terribly challenging. If you can pull it off, the BEST thing is to have a friend with a kit so you can just pop in on a Saturday with a six pack and your friend can bleed your brakes while you tell him or her how awesome he or she is.

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    Quote Originally Posted by ImaCynic View Post
    Ok, I am surprise to see that Shimano system does not have a way to prevent this behavior. I use TRP HY/RD calipers and do not recall seeing anything about not turning the bike upside down. I do so on regular basis and have not experienced this issue.

    If this is normal behavior, then I really like to hear why the shop replaced the brake.
    The TRP HY/RD are the cable-actuated hydraulic brakes, right? Seems that compact hydraulic system would be easier to seal, and keep sealed, than one involving hydraulic lines to the brake levers.

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