The Shimano BB-UN100 68/122.5 bottom bracket that came with my 2018 Giant Roam 2 feels rough and creaks.
Searching the web, it is hard to find new BB-UN100 brackets. I would like to upgrade to a better bracket.
I see a variety of Shimano UN300 68/122.5 brackets available online. But it is not clear to me what the difference is among the different versions of this bracket.
What else should I be looking for to determine which version of UN300 would work with my bike?
With Shimano square taper bottom brackets, the things to look for are the size of shell (68 or 73mm) and the axle length (In this case 122.5). A third important parameter is the threading size and pitch. Your bike has a BSA threaded BB shell (1.37 inches diameter x 24 threads per inch) and requires a bottom bracket of the BSA threaded standard.
Here's Shimano's current line up of square taper spindle bottom brackets. Note the three versions of BB-UN300 with either 122mm or 123mm spindle. Two of the three model numbers are followed by a letter. The letter K denotes the bottom bracket that should be used if the crankset is used with a Chaincase. If your bike has an "E-type" front derailleur, which is one that attaches to a plate that is secured by the bottom bracket cup, there is a BB-UN300-E for that purpose. If neither is true for your bike, then select the BB-UN30O without a trailing letter.
