Singlespeed & Fixed Gear - chainlines @_@

um....
i have spent some time reading sheldon brown's chainline stuff....
and im still confused @_@

so lets say i have a formula hub and soma fixed cog, which sheldon suggests creates a chainline of 42.9....

if a crankset is listed as 42 with a 110 mm bottom bracket....what would the crankset's chainline be with a 107 mm? would it then be 39? or would be like, 40.5 (im guessing that because the spindle length is divided in two because its on both sides)...

The 3mm difference between a 110 and a 107 is on the drive side. NDS stays the same.

wat = NDS

ninja death syndrome?

non-drive side or ninja death syndrome, whichever you prefer. :lol:

i prefer ninja death syndrome lol
ok thanks i think i get it ;p

Thanks for the info, scrod. Also something i've been wondering for a long time about lining up chains.

The 3mm difference between a 110 and a 107 is on the drive side. NDS stays the same.

This contradicts everything I know about spindles. As far as I'm aware, the vast majority of current BB's are symmetrical, and so you would have the difference for chainline adjustments.

I could be mistaken, but even so, not all bottom brackets are asymmetrical.

I always thought the same thing and Sheldon says that most BBs made since the 90s feature symmetrical spindles but I've got two Shimano UN54 BBs in the bottom drawer of my toolbox - one 110 and one 107 - that definitely have a 3mm difference on the drive side and no difference on the NDS. Besides, how would a longer/shorter spindle on the non-drive have anything to do with chainline?


not all bottom brackets are asymmetrical.

You're also correct here. I've got a 103mm Sugino BB that is definitely shorter on both sides...which turns illd's confusion back up to 11. :lol:

I think you're right about the Shimano, but it still depends on the particular bottom bracket.

The NDS length doesn't affect the chainline, but it effects how you measure it (since the number in the spec refers to the total spindle length). Two symmetrical BB's that are 110 and 107 will only have a 1.5mm difference in chainline. It also affects chainstay clearance.

so 2 shimano BBs, one 110 and one 107, would have a chainline difference of 3... while a 110 and 107 sized symetrical sided BB would have a chainline diff by 1.5?? :eek:

right now im juggling between a number of different 144 bcd crank options, and going with the miche cranks to miche bb is sounding the best choice cuz i hear you can adjust the spindle a few MMs to get super straight....could have heard wrong...

Miche BBs are adjustable from side to side which is good because you can dial in a perfect chainline but a lot of people - myself included - have experienced issues with keeping the cups tight.

having a chainline that's off by 1-3mm really isn't anything to lose sleep over, though.