Hello,

My Shimano LX cranks are just about done, the NDS crank arm keeps falling off and it looks like the threads are shot on the dust cap along with the spindle being marred up these cranks have been in service for over 5 constant years.

Anyways instead of buying a whole new crankset I am have a older Shimano FC-M521 crankset and can get a Octalink bb pretty cheap. The recommended is a 121mm so I would get a 73x121, however I am using a IGH so the cranks are setup SS. Would going down to a 73x118 be a better option for chainline?

I am on a Surly Ogre with a Nuvinci N360 hub and gearing is 32x16.

I see that NuVinci hubs have a 49mm chainline. *deleted incorrect info.

Thanks for the info.

https://www.shimano.com/media/techdoc...9830657937.pdf
This tech doc says the chainline with a 121 would be 50mm which is close enough on a 49mm chainline, i just though I could go down to a smaller bb since I am not setting it up as a triple.

Ah, my bad. Should have checked my memory against Sheldon. 47-50mm is standard chainline for MTB triples. But anyway, I would just use the 121mm bb for the 50mm chainline.All About Bicycle Chainline