Bicycle wheel metal or carbon fiber rim which holds a pneumatic rubber tire. A hub is the center part of a bicycle wheel. It consists of an axle, bearings and a hub shell. The hub shell typically has two machined metal flanges to which spokes can be attached. Hub shells can be one-piece with press-in cartridge or free bearings or, in the case of older designs, the flanges may be affixed to a separate hub shell. The axle is attached to dropouts on the fork or the frame. The axle can attach using a: Modern bicycles have adopted standard axle spacing: the
Reinventing the wheel the standard solution or does not understand the problem or the standard solution sufficiently to avoid problems overcome by the standard. It is mostly an affliction of inexperienced engineers, or the second-system effect. Many problems contain subtleties which were resolved long ago in mainstream engineering (such as the importance of a wheel's rim being smooth). Anyone starting from scratch, ignoring the prior art, will naturally face these problems afresh, and to produce a satisfactory result they will have to spend time developing solutions for them (most likely the same solutions that are already well known). However, when reinventing the wheel