[pursuiter]

I know it's not exactly a SS, I'm hoping you folks can help me.

I ordered a set of the single ring $38 Shimano DX cranks off of ebay. I need to order the correct BB. My Motobecane Outcast 29er frame has a 68mm BB and my hub is an I-Motion 9 hub with 50mm chain line (135mm spacing). I'm looking at using the Shimano ULN26 or ULN54 BB.

- What's the difference between the ULN26 and the ULN54?

- Which 68mm BB spindle width should I order, 113mm or 117.5mm or another width?

- Is there a better low cost square taper BB?

edit: ouch, just looked and the ULN54 comes in 113mm, 115mm and 118mm

 

[grawbass]

I'm running those cranks on two different bikes. 113 on one and 120 on the other. Depends on the chainstays. You'd probably be safe with the 118.

 

[Shadowhand]

I believe the UN54 has a hollow spindle, and the UN26 does not. My LX cranks use a 68/113mm BB, but I would ask your LBS to be safe.

 

[pursuiter]

Thanks for the replies, I went with the 118mm ULN54. I have an older Giant 68mm/135mm with similar cranks and I used a 118mm on it. Chainline on the Giant looks like 50mm with the 118mm. I'd ask my LBS except this kind of project always seems to be too weird for them to help out on. For me, it's easier to take a chance, mail-order it and if it doesn't fit, I'll have a use for the extra BB on another bike. I always have a bike project on the burner

 

[pursuiter]

UN54 does have sealed bearings. The 118mm gave me a 49mm chainline, just about perfect :thumbsup: