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  1. #1
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    Does your frame have...

    ... a small hole in the bottom of the BB shell? Some of my older bikes have one, but I just removed my BB & it was full of water in there.
    Any wisdom as to why frames don't have the small drain hole these days.
    Just wondering...
    Drink coffee....ride bikes....eat cake
    http://morayfatbike.blogspot.com

  2. #2
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    Most frames only has a hole to bolt on the under BB cable guide, so have been dropped from most modern MTB's.

  3. #3
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    Quote Originally Posted by motorman View Post
    ... a small hole in the bottom of the BB shell? Some of my older bikes have one, but I just removed my BB & it was full of water in there...
    Many people believe that it's possible to keep moisture out with seals. I'm sure it is in precisely controlled conditions.

    It's even better to allow any trapped water to escape though.

    The point of seals is to keep grit out IMO.

    In the pre mtb days bikes were oiled at the BB rather than greased (grease a hinge, oil a bearing I was told) and the bearings were expected to last. Frequent oiling*, especially after wet use was the norm. Custom bikes often had big holes in the BB with no adverse effect.

    A sealed bearing is best filled with grease IMO. This is because when the bearing is used it gets hot. Any air in there expands and blows past the seals. When you stop the bearing cools down and now you have low pressure inside the bearing. Air gets sucked in and if that air is moist then you have the conditions for rust.


    *Apart from lubrication, this also served to flush out any grit, so the BB remained clean..
    As little bike as possible, as silent as possible.
    Latitude: 5736' Highlands, Scotland

  4. #4
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    I drill all my frames under the BB if there is no hole, even used to on new frames
    4mm hole lets any water out, would need to be bigger to let marine life out though
    plan it...build it....ride it...love it....
    http://coastkid.blogspot.com/

  5. #5
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    Quote Originally Posted by motorman View Post
    ... a small hole in the bottom of the BB shell? Some of my older bikes have one, but I just removed my BB & it was full of water in there.
    Any wisdom as to why frames don't have the small drain hole these days.
    Just wondering...

    I have been thinking of adding one of these dry valves: Action Tec

    Seems cheap insurance for ~$8.

    g

  6. #6
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    Quote Originally Posted by coastkid71 View Post
    I drill all my frames under the BB if there is no hole, even used to on new frames
    4mm hole lets any water out, would need to be bigger to let marine life out though
    I'm aware this is considered good practice with steel frames but what about aluminum? Beach riding or exposure to salty environs could still result in corrosion within the BB shell correct?
    38 54' -77 15

  7. #7
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    [QUOTE=coastkid71;8819826]I drill all my frames under the BB if there is no hole/QUOTE]

    That's exactly what I will be doing next time I'm in the man cave
    Drink coffee....ride bikes....eat cake
    http://morayfatbike.blogspot.com

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