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  1. #1
    mtbr member
    Reputation: A1an's Avatar
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    Jun 2007
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    Monocog...frame rust and BB replacement

    Well it is finally time to replace the lead anchor BB on my '08 Monocog. Despite how cheap I would imagine the stock square taper BB is, this thing has done its job well. I have submerged my bike more times than I can remember and it just keeps going...but I think my abuse has finally caught up with me.

    The shell is so corroded/rusted that I cannot make out the size and manufacturer of the BB. Am I correct in assuming it is a standard 68mm square taper BB? What would you guys/gals recommend as a replacement? I'm looking to drop some weight but I don't want to completely sacrifice durability.

    My other question is rust. As stated before the bike has been through some water a few times. After each time I remove the seatpost, drain the frame, and leave it out for a few days for any residual to evaporate. Last time I had the BB out was maybe a year ago. Interior of the frame maybe had a little surface rust but nothing crazy. Today I took the BB out again and the rust is substantially worse. Hind sight I should have used Frame Saver when I first bought the bike. Is it too late to use a frame saver type product? I love this frame and want it to last...just hope I can do something to prevent future rot.
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  2. #2
    mtbr member
    Reputation: TiGeo's Avatar
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    The OEM BB is a VP 68x110 square taper. I replaced mine with a Shimano UN-54. They can be had for about $20-25 off ebay. Bullet proof and cheap. Don't worry about the weight. There are not many choices anymore for lightweight square tapers but to me, dropping over $100 on a Phil Wood etc. on a bike that was only $450 is a waste of money.
    Geologist by trade...bicycle mechanic (former) by the grace of God!

    2012 Specialized Stumpy EVO 29 HT

  3. #3
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    Reputation: adamfss's Avatar
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    Nov 2008
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    Just had the same issue with mine. Went with a standard truvativ. $20 installed at the LBS. IMO shaving weight on a MC is like trying to shave a pound off an Abrams tank.

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