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Old 09-13-09, 05:01 AM   #1
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BB spindle length?

I have a Motobecane Messenger FG/SS that I spread the rear triangle to wedge a SRAM S-7 internal gear hub into. Since this hub is wider than the stock flip-flopper my chainline isn't straight anymore leading to a lot of chain-dropping. I'm cool with buying a new BB but I'm not sure what spindle length I need. I believe the stocker is a 110mm so I'm guessing I need a 113 or 115mm but I'm not sure? Anyone know how I should approach this?

Thanks in advance.

and an art shot:

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Old 09-13-09, 05:52 AM   #2
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Measure your chainline at the rear hub. Measure in millimeters.
Measure your chainline at the chain ring.
Calcluate the difference. Add or subtract twice the difference to your current BB spindle length.
Alternately, if the difference is small, you may be able to space the cog, but new BB spindle is the best approach.

Last edited by Steev; 09-13-09 at 06:33 AM. Reason: Add link to SB's chainline page
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Old 09-13-09, 01:05 PM   #3
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Hello I would have the frame alignment checked, to ensure your frame is still straight and your rear triangle is not just offset to the left.

also I think you just solved a problem for me. a coworker bought a bike off ebay but it came broken. he told me it was shimano but I can't find a shimano 7 IGH that has a rod mechanism to shift it. Thanks for the tip
Bianchis '87 Sport SX, '90 Proto, '90 Campione del Fausto Giamondi Specialisma Italiano Mundo, '91 Boarala 'cross, '93 Project 3, '86 Volpe, '97 Ti Megatube, , '90 something Vento 603,

Others but still loved,; '80 RIGI, '80 Batavus Professional, '87 Cornelo, '09 Motobecane SOLD, '?? Jane Doe (still on the drawing board), '90ish Haro Escape
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Old 09-13-09, 04:19 PM   #4
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Neither of those 3 pictures tells us anything about the chainline. Especially the last two. And what crankset are you using please?
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