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
Rim (wheel) rim and then being welded together. The disk is welded in place such that the center of the wheel is equal to the center of the hub. The distance between the centerline of the rim and the mounting plane of the wheel is called the "offset" and can be positive, negative, or zero. One-piece rim and wheel assemblies (see image) may be obtained by casting or forging. The terms "wheel" and "rim" are often incorrectly used synonymously, as in decorative wheels being called rims. Used broadly, or used figuratively, the word "rim" can mean the outer edge of any circular