Back in 2000, Cannondale revolutionized bottom bracket technology by oversizing the bottom bracket shell and replacing the heavy, flexy steel BB spindle with a 30mm aluminum spindle with a unique, stress-reducing wave-taper crank interface. The result was BB30, a system that is not only significantly lighter, but also significantly stiffer than traditional designs. We released the design as a free industry standard and the rest, as they say, is history. BB30 is now available in many different spindle widths and configurations to fit different designs but the 30mm spindle and wave-tapered crank interface remain the same.
An example of this is the new BB30A found on the Synapse. The "A" stands for Asymmetric. BB30A adds 5mm to the non-drive side of the BB shell, allowing for a wider, stiffer base, while still maintaining ideal chainline and even ankle clearance on both sides.
The BB30 spindle interface