[JoeandEaston]

I am running a 68x113 un72 bb on my Misfit Dissent. I have it set up as a 1x9 for now. I want to move the chain line in board .1" so as to better line up with the middle of the cassette. If I get a 68x110 bb will that move each side equally or the fixed cup side 3mm? I guess if it's equal, I need to get a 107?

I know that with square taper the crank engagement is not that precise or consistent between BB and cranks.

Sorry if this is a stupid or simplistic question.

 

[mtnbiker72]

going to a 110mm will move it in 1.5mm or .06", 107mm will be 3mm or .12"

You don't mention the crank your using or what position your single ring is in. Most square taper cranksets have a 47.5mm chainline (measured at the middle ring) with a 110mm BB spindle. This would be ideal for a 1 x 9.

 

[JoeandEaston]

I am running some old XT compact 5 bolt cranks. FC-M737. I measure the chainline to be 49.88mm (1.965") to the middle ring. If I am understanding you correctly, I would need a 107 to give me a chainline in the middle of my rear cassette. I measure the middle of the cassette to be 47.16mm or 1.857"

 

[mtnbiker72]

Well Shimano actually measures to the inside of the ring so your probably closer to 49mm right now. If you put a 110mm you be closer to 47.5mm, which is where you want to be in the middle of the cassette chainline.

 

[N10S]

I just changed-out a 113mm Un72 for a 110mm Un72 on a Salsa Fargo I just built. I am using a set of 737 XT cranks with a 32T salsa ring in the middle ring position. The 113mm spindle put my chainline too far out up front, but the 110mm puts it right in line with the middle of the cassette.It was the same situation with my 1x9 Bandersnatch as well. The UN 72 is a great BB.

 

[JoeandEaston]

yea, I'd love to have another un72, but all I can find are un52's. Anyone have a link for a un72 they can give me?

 

[DeeEight]

The correct BB length for the 737 cranks is actually 107mm to hit the 47.5mm chainline shimano used to call for.