Rotor bsa 30mm steel bottom bracketrotors bsa30 bottom bracket allows the installation of our 3d bb30 cranks into a standard threaded bottom bracket the bsa30 is available in black colour with steel bearings or red with enduro grade5 ceramic bearings the steel option offers a light and elegant bottom bracket at a very competitive price while the ceramic bearing options are ideal for those looking to shed every possible gram while at the same time acquiring an incredibly smooth bottom bracket