Description

Rotation Engineering’s new BSA is our most evolved model. Of course, it’s still made right here in Connecticut out of U.S.-sourced 7075-T6 aluminum. It shares some carry-over tech from our experience with the original version like the accurate thread geometry and the precise bearing bore press fit tolerance. Almost everything else has been updated! Small but necessary refinements have always set our products apart and we didn’t hold anything back on this new version. We modified the back of the cup with a small standoff so that it would align better with the frame after chasing and facing. Your bike shop can now face the frame with the smallest 44mm or 45mm BB face cutters instead of using the much larger 57mm cutter that was previously recommended. We revised the gap geometry between the outer flange of the cup and the reducer’s flange to create a tight-fitting, zero contact labyrinth seal. This new design keeps friction to a minimum but also repels low-pressure water and grit better than the previous design. We have added a hydrophobic Nano-particle paste to the inside of the bearing reducer flanges and outer bearing seal to add even more protection against water ingress and contamination. A square cut seal has been added to the outside of the reducer where it meets the crank arm and spindle to seal this critical area better than the V1. Next we went to work on the chassis. The original chassis with three components (2 cups and 1 spacer) has been simplified. It has only two chassis parts since the drive side cup now has a one-piece center spacer machined directly into it. The new design, while more time consuming to manufacture, eliminates one potential water ingress point and some excess overlapping material. We still offer two pre-assembled bearing options STANDARD and ULTIMATE (description below). For frame and crank fitment we support three crank spindle diameters (29mm-24mm/30mm) and two frame width options (68mm-73mm). Crank spindle spacers are not included.

The STANDARD bearing option features hardened 52100 high chromium races, cage, and ball bearings, two low friction rubber seals and a specially formulated anti-corrosion low friction bearing grease. This option is for the more budget-oriented customer that still wants a premium USA-made bottom bracket.
The ULTIMATE bearing option features one low friction rubber seal facing out, one non contact PEEK shield on the inside, a PEEK bearing cage, a specially formulated ceramic-bearing-optimized, low-friction grease, grade 3 silicon nitride balls, a d hardened 52100 high chromium bearing races that have been isotropicly polished and coated with WS2 & TDC for the ultimate blend of durability and performance. This option is for the consumer that wants the ULTIMATE, period!