XTR(FC-M900) crankset: compatible bb?

[JBF]

I've purchased a first generation XTR crankset(FC-M900). The Shimano
Small Parts Catalog states the use of Model BB-UN90 (113mm or
107mm)only. I believe I can use the current BB-UN72 in 113mm spindle
length to maintain the 50mm chainline.
It's a decade old catalog & I don't believe they made another
compatible bb in a 113mm length at that time.If anyone can offer
insight I'd appreciate it.

Thanks,
JB

[rocketman58]

The current UN73 BB in 107mm will work perfect. That is what I am
using right now. I have used the older UN72 as well. The 107mm x 68
provides the correct chain line for my Ti hardtail. I can not imagine
using a 113mm (maybe a 110mm for certain frames with some clearance
issues).

The crank provides a pretty wide "Q" factor. With a 113mm wide BB,
your feet would be pretty far apart, and it would not provide the
correct chainline in my experience. I tried a 115mm BB for use with a
4th inner chainring. While this did work, the "Q" was so wide, I
found it uncomfortable (and I have pretty wide hips).

When I used this crank on a roadbike, I used a 103mm Dura-Ace BB. It
worked perfect for the road bikes 130mm rear wheel spacing.

Did I mention that in my opinion, this is the best crank ever made?

"Thumbie", XTR-M900 crank with 46,34,20 chainrings.

raz...@yahoo.com (JBF) wrote in message news:<bedb1122.0405...@posting.google.com>...