83mm BB spacing

Discussion in 'Downhill & Freeride' started by big-ted, Jan 5, 2008.

  1. big-ted

    big-ted Danced with A, attacked by C, fired by D.

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    Can anyone tell me how far apart the cups should be spaced on a Shimano 83mm BB?

    For example, the 73mm version has to be spaced 75.5mm, which is why a 73mm shell needs one 2.5mm spacer, a 68 needs 3 spacers etc. The 83mm BB came with 3 spacers but I find it hard to believe the total spacing has to add up to 90.5mm...
     
    #1 -   Jan 5, 2008

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  2. big-ted

    big-ted Danced with A, attacked by C, fired by D.

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    Weird. Shimano's tech docs say use all three spacers... Who am I to argue?

    clicky
     
    #2 -   Jan 5, 2008
  3. FrontRangeDH

    FrontRangeDH Monkey

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    I was using all 3 spacers on my bikes and my roommates when I built my Glory and his Session 10
     
    #3 -   Jan 5, 2008
  4. Curious_George

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    you forget that the spindle length is much greater on the 83mm Crank...treat it basically like if it was a 68mm like you mentioned with 3 2.5mm spacers [depending on your setting]
     
    #4 -   Jan 5, 2008
  5. big-ted

    big-ted Danced with A, attacked by C, fired by D.

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    Yeah. Currently I have two spacers and a BB mounted chain device which, in truth, may be a little thicker than 2.5mm. I'm just trying to figure out why my BB had died within about 3 months.
     
    #5 -   Jan 5, 2008
  6. caputo1989

    caputo1989 Turbo Monkey

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    Octalink/ISIS?
     
    #6 -   Jan 5, 2008
  7. khoolhandz

    khoolhandz Chimp

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    Huh? Didn't know about that. I thought the spacer is simply to give you a better chainline more than anything else.

    I have an 83mm BB and don't use any spacers since I don't need to.
     
    #7 -   Jan 5, 2008
  8. big-ted

    big-ted Danced with A, attacked by C, fired by D.

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    Hollowtech 2 (Saint)

    Well, you can vary the chainline by which side you put the spacers, but the total shell length should be fixed.
     
    #8 -   Jan 5, 2008
  9. khoolhandz

    khoolhandz Chimp

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    Should have read more carefully, you were referring to the shimano outboard type bb. doh!
     
    #9 -   Jan 5, 2008
  10. DirtyMike

    DirtyMike Turbo Fluffer

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    Well, no actually the spacers are not for chainline. The spacers are going to make your cranks sit evenly on each side, your chain line is going to be figured by spindle length.The spacers are not just for fitting issues, They also offer some protection to the BB cups themselves, you dont want your cups right against the shell, you will usually always see at least one spacer per side. Most 83mm shells will have one spacer on the nondrive side and two ont eh drive side, removing one drive side spacer for use with an Etype mount, either a derailer or chain device. Same for a 68/73 shell setup, 68 has two on the drive side, one on the non drive side, But a 73 shell will have one on each side, removing the driveside spacer when using an etype device..

    Problem with most 83mm shells is you dont get much choice at all for chain line.
     
  11. DirtyMike

    DirtyMike Turbo Fluffer

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    Just to add, I wasnt trying to be condesending or anything like that, Its just a common mispercecption about bb spacers is all.
     
  12. pinkshirtphotos

    pinkshirtphotos site moron

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    z man should be able to help being he was a shimano race mechanic
     
  13. DirtyMike

    DirtyMike Turbo Fluffer

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    This should be correct, with one spacer on the non drive side, and the Chain device and other spacer on the drive side.
     
  14. DirtyMike

    DirtyMike Turbo Fluffer

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    Just curious, But did you have your BB shell faced before installing your BB?