Originally Posted by
Iride01
It seems the UN300 has some engineering to address issues that people have with the UN55 when the threads are not cut perfectly on the same axis between the drive side and non-drive side. Which seems like it might be an issue in several BB threads post here at BF with other cartridge BBs as well as the UN55.
What's been done to help?
I ran into this issue recently with an eBay Ti BB. For practice, I tried installing it onto an MTB (Jamis frame, should be reliable quality). The old BB was a NECO brand and spun well, but the eBay BB did not when installed, specifically because of the above issue.
So how was it that the NECO worked? There was play in the NDS cup diameter vs bearing that allowed the NDS cup to angle out of alignment, but yet not create any slop with the bearing. That sounds impossible, but that's how it worked.
The eBay BB on the other hand was a tight friction fit between the bearing and cup. So any misalignment caused binding to the bearing.
How are we to be sure when buying BBs that the design accommodates for this? Getting a frame re-tapped is a poor suggestion IMO.