Shimano didn't forget about the Bottom Bracket when redesigning their Dura-Ace group. Compared to its predecessor, the BB-9000 manages to simultaneously shave weight and boost efficiency, all while maintaining industry leading weather resistance and durability.
These improvements are made possible thanks in part to the redesigned cups and bearings. The external cups have been reworked using a slightly smaller diameter, allowing Shimano to shave a few grams off the 7900 model. The new cups call for slightly smaller bearings as well, furthering the weight reduction. Finally, updated seals allow them to drop resistance by a claimed 50%, reducing effort required in pedal stroke with no sacrifice in weather resistance.
The Dura-Ace BB-9000 Bottom Bracket is specifically designed for the Dura-Ace FC-9000 Crankset, but is compatible with all Shimano Hollowtech II road cranksets. Available in English (68mm shell 1.37 in x 24 TPI) or Italian (70mm shell 36 mm x 24 TPI) threading.
Note: The BB-9000 features a slightly smaller spline diameter than a typical Shimano bottom bracket cup. An adapter is included for use with standard Hollowtech II-compatible bottom bracket tools. It can also be installed and removed using the Park Tool BBT-29 Bottom Bracket tool.
A guide to bottom bracket standards.