Bottom bracket drain holes?

Discussion in 'Cycling Equipment' started by stang106, Jan 20, 2005.

  1. stang106

    stang106 New Member

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    I have a new aluminum frame, and it does not have drain holes like my old steel Italian frame. Should I drill a hole or two in the bottom bracket for a drain or does this compromise the integrity of aluminum bottom brackets? I was wondering what the norm is?
    Thanks,
    Dave
     
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  2. bikeguy2004

    bikeguy2004 New Member

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    Based on the posts in anther forum… The consensus was, if you ride in wet weather a lot you probably should consider drilling a drain hole in the BB to allow the water to exit the BB. The idea was that you drain the water before it can cause any problems with the BB bearings, etc… Personally I don’t ride in the rain that often, and I can’t bring myself to drill holes in my titanium BB. So my bike has no extra holes.

    Of course if you do drill a drain hole in the BB, first you should remove the BB and select a location that is lowest on the BB to allow the water to drain. And be sure to get all of the metal filings out of the BB before you reassemble it.
     
  3. boudreaux

    boudreaux New Member

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    There is no worry about bearings with a cartridge BB. The BB doesn't even have to be removed.
     
  4. Conniebiker

    Conniebiker New Member

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    While it can be done assembled, it is much better practice to not have the bearing cart in place during the operation.
    Another thing is even on an aluminum frame, you should look into touchup paint for the inside of the hole, since that breaks the skin of the paint.
     
  5. artmichalek

    artmichalek New Member

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    On that note, you should also chamfer the edge of the hole with a countersink bit. Paint doesn't like to stick to sharp right angles.
     
  6. boudreaux

    boudreaux New Member

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    That is just nonsense.
     
  7. boudreaux

    boudreaux New Member

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    More nosense.
     
  8. boudreaux

    boudreaux New Member

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    Forget the rocket science and just give it a dab of clear fingernail polish.
     
  9. stang106

    stang106 New Member

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    Rain? Here on Vancouver Island? Yep, and since I need to crank out many six-plus hour rides before my next race rain and wet roads are unavoidable.

    I'll put two holes aligned where the holes in the cable guide are. 5/16" should do it. Chamfering is actually the standard for holes; any machine shop will chamfer a hole unles given other instructions. I'll put on a light chamfer and touch up the bare aluminum. The frame is new and unassembled now, I've alredy chased all threads with a tap to remove paint and avoid assembly and riding problems.

    Dave
     
  10. boudreaux

    boudreaux New Member

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    Ya know, I'm still waiting for one of my frames to fail due to my my lack of attention to this rocket science detail. Mybe you ARs ought to check the hole for the cable quide sometime.
     
  11. stang106

    stang106 New Member

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    ARs? I also have a race car (70 Mustang) and have done alot of fabricating. Chamfering is the norm to remove the burr left by the drilling process so the bolt head/washer can sit square and not develop a high tension area under load. Also burrs can catch skin and fabric. I like to pay attention to the little details before they turn into big problems.

    Dave
     
  12. boudreaux

    boudreaux New Member

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    A drain hole in a bicycle BB shell is not a big problem area. But, if it gives ya a nice warm fuzzie go ahead and knock yerself out.
     
  13. dhk

    dhk New Member

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    Two 5/16" holes seems a bit much for a BB drain to me, but suppose they couldn't hurt anything. My AL bike has a single drain hole, appears to be about 1/8" which I believe is more typical.

    Agree it's nice to deburr a hole, but I don't call that chamfering. If I have burrs after drilling, usually will just pick up a larger drill bit and take the burrs off by hand.
     
  14. boudreaux

    boudreaux New Member

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    Yeah...........
     
  15. artmichalek

    artmichalek New Member

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    Agreed that unless you're taking the bike for a swim, a single 1/8" hole should be more than enough to get the water out. By chamfering, I actually meant cutting the metal back about 1/64" around the edge of the hole with a 45 degree countersink bit. It's not really necessary, but in my opinion holes look better that way after they're painted.

    Opinions on machining practices aside, it might be worth noting that with an aluminum frame not all of the water is going to drain into the bb shell anyway. The effort spent drilling drain holes might be better applied to making sure everything is sealed up so you don't get water in the frame to begin with.
     
  16. Conniebiker

    Conniebiker New Member

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    Boudreaux-
    Please try to sound a little more orderly, than simply saying "Nonsense" to everything.
    I speak from experience of being a car/bike/aircraft restorer. I am A full aircraft mechanic,which involves 3 months of metalurgy and paint sciences in the 18 months of full time classes.

    Chamfering is indeed overkill for the application, but a nice touch. Deburring is all that is needed, as was stated with a large drill bit. One hole. The rate of influx of water is not enough to outrun that unless it was in a river crossing or the like.
    While the aluminum will not turn into a rusty mess like if you did this to steel, it is still important to seal the skin of the paint after such an operation because the edges of the hole allow corrosion and moisture to creep in under the paint. Just ask anyone who deals in painted metal. If you are too lazy for paint, car wax is effective. But why fall short of a good looking machine? It would take a matter of an additional 10-15 minutes if that, to achieve a factory looking job. No it is not going to fatiue itself to bits or fall apart it if isn't treated as such, but why settle for almost?
     
  17. dhk

    dhk New Member

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    I'm not worried about corrosion on my AL/CF frame. It only has a 3 year performance warranty, and I'm planning to ride so many miles and get so strong that I'll wear it out shortly after the warranty period ends.
     
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