CeramicSpeed PF4630 Bottom Bracket - Specialized OSBB / BB30

OSBB is the acronym for Specialized’s OverSized Bottom Bracket. It features a 46mm diameter and 61mm width shell. As it is unique, it requires a unique bottom bracket to mate BB30 cranks to it.

The cups come installed with one of two CeramicSpeed bearings. The Standard Bearing has ceramic CS balls and hardened-steel races. The Coated Bearing has the same balls running on hardened-steel races with a 3-micron thick metallic coating making the races harder and smoother, increasing service life and reducing friction.