Asymmetric, stiffer, lighter: BBright™ is the only Bottom Bracket standard that uses an oversize 30mm axle and allows for oversized frame tubes (up to 16% wider than standard bottom brackets). It offers the optimal combination of stiffness and weight for the overall system (crankset and frame together).
In the past, frames and cranks were designed to work with existing bottom bracket standards. We recognized that these existing standards limited system performance. By designing the crank and frame together, as a system, BBright yields a significant increase in system performance. BBright was designed with the widest range of crank options in mind while allowing us to offer the stiffest frame possible.
First, we decided what not to change: the derailleurs, chain line, and pedals (Q-factor, or stance width) all remain in the same place for best drivetrain function and familiar ergonomics. We looked next at what parameters would optimize performance of the whole system (frame + crank). For the crank, a 30mm axle is stiffer, lighter and directly compatible with easily available Press Fit 30 bottom brackets. For the frame, BBright’s 79mm bottom bracket shell permits oversized frame tubes that save weight and increase stiffness, addressing a major limitation of old 68mm bottom bracket standards.
How did we get to 79mm? On the left side, compared to external bearing bottom brackets with 68mmm shells, the bearing in the same position, but we replaced the metal bearing cup with frame material. This allowed us to increase the left side chainstay width by nearly double. On the right side, compared to BB30’s 68mm shell, we kept the bearing in the same position, leaving room for power meters and compatibility with existing BBB30 crank molds. Also, the tubes can’t get any wider on the right: they’re already limited by chain and chain ring clearance, so making the shell wider doesn’t improve performance.
The net result is a stiffer, lighter crank and a stiffer, lighter frame, a natural result of our system engineering approach. BBright truly combines system optimization and simplicity.