Originally Posted by
Tourist in MSN
I am not sure what a UN51 is, I have a UN55 on my expedition bike, nothing wrong with it.
With 15k miles on your old one, might as well put on a new one when you are at it since they are about $20 or so. Since I do not know what a UN51 is, I assume that the UN55 uses the same tool to install in the frame, but you would need to verify that.
Thanks for the tips and crash course on BBs, everyone. I've never had to replace one, so this is all a bit new to me. The Shimano UN-55, from what I understand, is just the successor (a few times over) of the UN-51. I also noticed that it's what Surly puts on their disc truckers, so it must be decent and take some serious milage.
The text on my original BB reads "1.37 x 24" on one side and "1.37 x 68" on the other.