Cranks and bottom brackets have a decisive influence on the overall performance of a bicycle. Clean running, good power conversion and high load capacity are existential factors when choosing a crankset. Shimano produces a large assortment of different cranksets and matching bottom brackets. Thereby an optimally suitable system is available for every bike and every discipline. Hollowtech II works with 24 mm axes or bearings After analyzing all the factors and carrying out tests, we decided on axes and bearings with a diameter of 24 mm. This provides the highest possible balance of rotational efficiency, rigidity, load capacity, tightness and weight in proven Shimano quality. "Press-in Bottom Bracket Bottom Bracket for Press-in Assembly features 24mm diameter shafts and bearings because it provides the best combination of rotational efficiency, stiffness, load capacity, tightness and weight, even with press-fit bearings.