Rotor bb30 to 24mm steel mtb bottom bracketour ingenious bb30 to bb24 converter bb which allows the installation of conventional bb24 cranks in bb30 frames using our new non contact labyrinth seals rotor has been able to achieve a buttery smooth feel along with unparalleled protection against dust water and mud available only with steel bearings in black available only with ceramic bearings in red compatible with all conventional bb24 cranks manufactured by rotor shimano and shimano com