The hub is the central part of the bicycle's wheel or wheelset. There are different kinds of hubs for front and rear wheels as they have different functions. The hubs connect to the rims via the spokes and sit at the axis of the wheel. Bicycle hubs are also bike-specific. You need to choose one based on the kind of bike you ride, be it either MTB, road bike or BMX.Front and Rear Hub Differences
The front hub simply allows the bicycle wheel to spin. It contains a metal tubular body with a set of bearings at each end, either cartridge-type or loose ball bearings. The wheel axle spins on these bearings. The rear hub forms a part of the bicycle's transmission as the sprocket or cassette that drives the rear wheel attaches to the hub. The rear hub usually includes a mechanism that allows you to freewheel.MTB Hubs
The choice of the right MTB hub depends on your riding style, as the selection is indeed vast. A lightweight racing alloy hub, for example, gives you the perfect competitive edge, but cannot cope with downhill riding or lots of dirt. You also need to consider the type of bearings: either easy-to-clean older cup and cone bearings or convenient, but more expensive cartridge bearings. In addition, you need to choose your preferred material, either lightweight aluminium alloy or even the high-end carbon fibre. When choosing the MTB hub, do not forget your axle type and brake rotor compatibility either.Road Bike Hubs
Similarly to the MTB hubs, you need to decide whether you want simpler cup and cone or more convenient cartridge bearings for your road bike hubs. Instead of steel balls, you could also invest in high-quality ceramic bearings. In order to shed weight, the road hubs are quite minimalist in design. Compared to MTB bikes, the road bikes do have to handle fewer difficulties.BMX Hubs
BMX hubs include two or more sets of bearings and the latter need to be of high quality to ensure healthy and long hubs. High-end BMX hubs typically incorporate cartridge bearings. The BMX hubs have three further subtypes based on the type of freewheel they contain. The hubs could be belong to the freewheel, cassette or freecoaster type.