[gabe0807]

Hey everyone, I'm putting together a new single speed and ran across a problem I've never had before. In the past I used King hubs which some provided some chainline adjustability, so I never really worried to much about it. Now I'm using a Paul rear hub with a WI freewheel, so there's no adjustment there, so I have to get my BB spindle length spot on. I'm using some old square taper M900 XTR cranks. I know normal 3-ring setups usually have a 50mm chainline from the middle ring, but that is with what BB spindle length? I just need a reference point to start from. Any help would be appreciated. Thanks!

 

[cutthroat]

I know normal 3-ring setups usually have a 50mm chainline from the middle ring, but that is with what BB spindle length? I just need a reference point to start from. Any help would be appreciated. Thanks!

Actually, the older XTRs were more like 47.5mm CL. The new Hollowtech II series with the external BB bearings increased that to 50mm. Your spindle length Q factor and CL will depend on you BB shell width, 68 or 73, and the crank set up you are using. Typically, a 113 mm spindle length is "standard" for most mountain bike frames, but the older XTRs could run narrower BBs (112.5 I think)

 

[gabe0807]

Thanks for the quick info Cutthroat.

I just found that Sheldon Brown has a database for this as well. It agrees with what Cutthroat said: 47.5 to 50mm chainline for BB lengths of 107-113mm. Good Stuff. Here's the link:

http://www.sheldonbrown.com/bbsize.html#shimano

 

[cutthroat]

Yes - Sheldon is a great resource. So if you can make it work with your cranks, it looks like a 107mm spindle will get you a 47.5 cl.