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  1. #1
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    New question here. Single Set Up - UN72 BB Length Question

    I'm in process of building up my 2nd single speed ride. My 1st SS (SC Chameleon with Kona P2, Surley 1x1s, Magura HS33s & Turibe LPs) got quickly dismantled & sold as parts after the realization of what terrible shape I was in and my dependancy on 24-27 gears. Well, I am a few years older, a few pounds heavier with definitely less brain cells so I decided to give it a try again.

    Nothing that fancy this time. Retro inspired 7005 AL HT frame, generic 1x1 wheelset, 16T cog, Strongarm cranks, UN72 68x? BB, platform pedals, Marzocchi Z2 63mm bomber, Kore stem, Ovation dh riser, Cane Creek Aheadset, Koski Vs & levers, Oury grips, K2 post, Brooks saddle & IRC Back Country 2.25 knobbies. It's a really sexy, curvy looking ride, minus the paint chips from poor Bay packaging & group shipping. I'll post befor (stock 3x7) & after (1x1) pics when done.

    My question is this, with a square taper BB for compact 175 cranks...what's the recommeded BB spindle length for a good chainline?
    Thanks for any help.

    Scott
    Last edited by Scott_in_Jersey; 04-29-2004 at 11:34 AM.

  2. #2
    drev-il, not Dr. Evil!
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    Quote Originally Posted by Scott_in_Jersey
    My question is this, with a square taper BB for compact 175 cranks...what's the recommeded BB spindle length for a good chainline?
    Thanks for any help.

    Scott

    That's not easy to answer. There are factors like the width of your chainstays, whether you are going to use a bashguard, etc. I'd suggest putting the cog on the wheel, put the wheel in the frame, eyeball, then take measurements. If you have a spare bottom bracket, or don't mind borrowing one from another bike, that would be better. The best is finding a cool shop that will let you exchange the BB if you discover it is not the right size.

    All said, I usually have the best luck with 113mm.

  3. #3
    nachos rule!
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    113mm oughta do you. i've got 1x1 hubs, and with either ritchey or shimano 94mm compact 5 bolt cranks a 113mm un72 is the ticket. i've got a park chainline gauge, and these setups check out perfect, not even a millimeter off. that's with the chainring mounted outboard.

    good luck, eric.

    ps: i'm guessing from the fact that it's bolded that you're wondering what the 68 means. that's the width of the bb shell. most bikes are 68mm, an occasional "heavy duty" inspired frameset will spec a wider 73mm shell. so your complete bb spec is model/shell width/spindle length, ie: un72/68mm/113mm.
    Last edited by supercorsa; 04-29-2004 at 11:56 AM.
    plus a change, plus c'est la m'me chose - alphonse karr

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