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How much thread engagement does a BB need?

Discussion in 'Downhill & Freeride' started by 1000-Oaks, Oct 2, 2005.

  1. 1000-Oaks

    1000-Oaks Monkey

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    I'm having problems with my chain rubbing on my wide 2.4" Panaracer FR tire, currently using a 116mm 68/73 BB on a 68mm Foes FXR shell. If I put both 2.5mm spacers (needed to use the 73mm BB on a 68mm shell) on the drive side, it gets me much improved chain clearance and doesn't cause any trouble on the other side.

    Using both spacers on the drive side means the BB threads only go about 3/8" into the shell on that side though.

    Is that okay?

    I'm not worried about the threads pulling out, just wondering if that puts too much load on too little shell on that side. Don't want to ovalize the shell, if that's possible. I could go to a 118.5mm BB, but that will only get me another 1.25mm per side.
     
    #1 -   Oct 2, 2005

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  2. zedro

    zedro Turbo Monkey

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    #2 -   Oct 2, 2005
  3. bigdrop05

    bigdrop05 Monkey

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    I have an ISIS 128mm for a V10. If you need it i can sell it.Looks to be in excellent condition.
    PM if interested..
     
    #3 -   Oct 3, 2005
  4. 1000-Oaks

    1000-Oaks Monkey

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    I'm kind of stuck with an XTR Octalink crankset, which really limits my BB options. The used cranks are really light and came with a frame I bought, so I don't really want to buy new ones just to go ISIS.

    Plus I already cut off the big ring for the kind of lower-speed trail riding I do, so eBay'ing the crankset isn't an option any more...
     
    #4 -   Oct 3, 2005
  5. zedro

    zedro Turbo Monkey

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    i would say its not worth the risk
     
    #5 -   Oct 3, 2005
  6. amateur

    amateur Turbo Monkey

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    Well, I can't say how much, but 3/8" definately isn't enough. Go to a narrower tire.
     
    #6 -   Oct 4, 2005