Hydraulic brake screwup leads to question...
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  1. #1
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    Hydraulic brake screwup leads to question...

    99% certain this one's on me. Okay, 99.44% certain.

    - Borrowed a set of wheels
    - Focused more on the cassette/derailleur side of things
    - Pulled brake lever (still in stand) and got that awful, mushy, you screwed something up feeling
    - Turned to see fluid running down the brakes, rotor

    That's when I noticed (and this part's embarrassing) the rotor on the borrowed wheel was 20mm smaller than my wheel. Yeah... I know.

    Replacing the wheel with the 160mm rotor yielded the same result - fluid leaving the system

    My theory:
    The pads hit the rotor half on / half off causing a tilt. That tilt did one or more of a few things:
    - Dislodged a seal; Fix: put seal back in place; fill/bleed... buy new pads
    - "Reshaped" the caliper; Fix: even more new parts!

    Guesses?

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  3. #3
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    Quote Originally Posted by OldChipper View Post
    Must. Resist. Commenting.
    Shut up

  4. #4
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    Quote Originally Posted by OldZaskar View Post
    My theory:
    The pads hit the rotor half on / half off causing a tilt. That tilt did one or more of a few things:
    - Dislodged a seal; Fix: put seal back in place; fill/bleed... buy new pads
    - "Reshaped" the caliper; Fix: even more new parts!

    Guesses?
    I'd guess a dislodged seal as well. I believe most piston seals are square O-rings. The piston probably pushed past the seal, letting it pop out of the groove. I bet you can't push the pistons back in because the seal is stuck outside of the groove.



    - Pulled brake lever (still in stand) and got that awful, mushy, you screwed something up feeling
    - Turned to see fluid running down the brakes, rotor
    Meh.. don't feel bad. One time I pulled the leaver without a wheel on the bike. Pistons popped out of the caliper. Landed on the floor. Along with most of the hydraulic fluid.
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  5. #5
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    Thanks Tig. That does make me feel better. Ya see that OldChipper?

  6. #6
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    One day, a penguin brought his bike to the mechanic, leaking fluid. The mechanic says, "leave it for a bit; I'll get to it after this bike I'm working on", so the penguin went out for a walk, and stopped at an ice cream shop. On his way back to the bike shop, he dripped a lot of the vanilla ice cream on his plumage. When he got to the bike shop, the mechanic says; "Hey, it looks like you blew a seal!".........
    "L'enfer, c'est les autres"

  7. #7
    'brifter' is f'ing stupid
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    Blew a seal...I laughed.
    #promechaniclife

  8. #8
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    Thatís funny

  9. #9
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    I'm not going to give you guys crap for doing unbelievably dumb arse shxT, for fear of mr Karma getting back at me, but FYI, Blowing seals can cause cancer in California I hear.
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  10. #10
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    You guys are a big help. CX - I'm posting this in the Wheels & Tires and General forums... after I get an ice cream cone.

  11. #11
    gazing from the shadows
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    I put brake blocks in on my MTB when I take my wheel off, unless it is JUST wheel off/wheel right back on and nothing else being done.

    I never used to, and it was not a problem. Guess what made me start?

    The same thing that made me buy some fluid and a bleed kit.
    .
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  12. #12
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    Quote Originally Posted by No Time Toulouse View Post
    One day, a penguin brought his bike to the mechanic, leaking fluid. The mechanic says, "leave it for a bit; I'll get to it after this bike I'm working on", so the penguin went out for a walk, and stopped at an ice cream shop. On his way back to the bike shop, he dripped a lot of the vanilla ice cream on his plumage. When he got to the bike shop, the mechanic says; "Hey, it looks like you blew a seal!".........
    This one's been around for awhile:

    https://www.youtube.com/watch?v=R9ETlTZoF1E
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  13. #13
    'brifter' is f'ing stupid
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    Quote Originally Posted by Srode View Post
    I'm not going to give you guys crap for doing unbelievably dumb arse shxT, for fear of mr Karma getting back at me, but FYI, Blowing seals can cause cancer in California I hear.
    It's completely ridiculous in CA. I bought a wood dowel at Home Despot a while back. Wood. It had the Prob 65 cancer warning sticker on it. Wtf?

    #promechaniclife

  14. #14
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    Quote Originally Posted by cxwrench View Post
    It's completely ridiculous in CA. I bought a wood dowel at Home Despot a while back. Wood. It had the Prob 65 cancer warning sticker on it. Wtf?


    It seems like I find the Prop 65 warning on everything these days.

    FWIW, I bought an appliance a few years ago that warned to wash hands after handling the electrical cord because of possible lead contamination. Not hard to believe when everything is made in China. Just put some melamine in the ground beef, nobody will know the difference!
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  15. #15
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    Quote Originally Posted by cxwrench View Post
    It's completely ridiculous in CA. I bought a wood dowel at Home Despot a while back. Wood. It had the Prob 65 cancer warning sticker on it. Wtf?

    Probably the adhesive or ink on the sticker!
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  16. #16
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    Quote Originally Posted by Srode View Post
    Probably the adhesive or ink on the sticker!
    Wood dust is on the P65 list.
    .
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  17. #17
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    Quote Originally Posted by Lombard View Post
    It seems like I find the Prop 65 warning on everything these days.
    Yeah? That's because things shown to cause cancer are pretty much in everything.

    I just looked. CA warns if exposure to the chemical in the levels present will cause MORE THAN a 1 case per 100,000 population increase in cancer in the population... over a lifetime... at the levels present. So that can mean a big dose once, or small doses over time.

    For birth defects, it is stricter. The warning is triggered at 1/1000 of the "no observable effect" level. So if birth defects are show to become a risk at 1 gram from a substance, the warnings are triggered at 1/1000th of a gram.

    Mostly what you are seeing are long term effects triggering the warning. Wood dust is not going to give you cancer from a weekend project. But if you have a home shop, saw and sand a lot of wood? That risk goes up.

    I would not worry about any individual warning on things that are not obviously dangerous (like brake fluid). Anything in plastic packaging is going to get labeled from the stuff in the plastic that touches it if nothing else. But seeing warnings on everything, that really shows how exposed we are on a daily basis to very small doses of many dangerous substances. Many of which have cumulative effects.
    .
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  18. #18
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    This is helpful guys. So, if I'm understand you correctly, I should get a wooden dowel (assuming hardwood?) and beat on the brakes while eating an ice cream cone?

  19. #19
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    Quote Originally Posted by QuiQuaeQuod View Post
    Wood dust is on the P65 list.
    When everything is on the list, it kind of causes consumers to disregard the warning labels I think.
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  20. #20
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    Quote Originally Posted by Srode View Post
    When everything is on the list, it kind of causes consumers to disregard the warning labels I think.
    Yep.

    The upside is that most will wonder when the see the warning on something they always buy. They might look into it, learn something. Maybe they will buy an option without the warning if it exists. That seems like a serious business opportunity to me : p65 warning free products.

    As for the CA law, the workplace stuff is WAY more important than the consumer stuff in terms of limiting exposure to carcinogens. That's where long term higher dose exposure is more likely to happen.
    .
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  21. #21
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    Well, I got the brakes sorted out...

    - Removed the c-clips that hold the pistons in
    - Pulled the pistons
    - Unscrewed the fluid reservoir cap on the backs of the pistons
    - Confirmed the fluid was low
    - Topped off with 30w
    - Installed new cork gaskets
    - Used a vice to reseat the pistons
    - Primed the pads
    - Reinstalled the caliper

    Working great!

  22. #22
    tlg
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    Quote Originally Posted by OldZaskar View Post
    Well, I got the brakes sorted out...

    - Removed the c-clips that hold the pistons in
    - Pulled the pistons
    - Unscrewed the fluid reservoir cap on the backs of the pistons
    - Confirmed the fluid was low
    - Topped off with 30w
    - Installed new cork gaskets
    - Used a vice to reseat the pistons
    - Primed the pads
    - Reinstalled the caliper

    Working great!
    Great. But.... did you figure out what was causing the problem? Or did the gremlin magically disappear when you opened the caliper?
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  23. #23
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    Quote Originally Posted by tlg View Post
    Great. But.... did you figure out what was causing the problem? Or did the gremlin magically disappear when you opened the caliper?
    If the cause was user error, I hope cause did not magically disappear!
    .
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