Series 2 BB adapters were developed in January of 2024 to address compatibility issues with some MFG specs of BB shells. Shown in the photos you can see that some bottom brackets have a rather large inside diameter counterbore on the drive side. When building on DSI fixtures and nominal 68mm BB shells, their counterbore and the shorter length of our (series 1) BB adapters don’t play nice together. The BB can walk off of the adapter to the point that it creates issues with the plane contact between these parts. This series 2 adapter addresses these issues. It has a larger OD, longer pilots, and relieved inside shoulders. If you use BB shells without the big counterbores you’ll be fine with the series 1 adapter. We recommend Paragon Machine Works. At this time the only Series 2 adapter we make is the BSA 69/74. If you need another size let us know.
