HASA 2012 Shimano 105 Carbon Flat Bar Road Bike 56cm Shimano BB-86 Bottom Bracket the assembly pressed into the frame. This creates high efficiency in energy transmission and great pedal feedback. The new cone-shape head tube design 1-1/8"*1-1/4" this adds strength and resulting in a rigid feel and higher turning stability. The perfect frame geometry provides the rider most comfortable riding position.