Hub gears or internal-gear hubs are a type of gear system used on bicycles. Hub gears are used mostly on utility bikes and various types of small wheeled bicycle, such as folding bikes. Hub gears work by internal planetary or epicyclic gearing, which means that the outer case of the hub gear unit (which is attached to the spokes) is made to turn at a different speed relative to the rear wheel's sprocket depending on which gear is selected.
In the United States and United Kingdom, hub gears are less common than derailleur gears which are the dominant gear system on most modern bicycles in these countries. In most of continental Europe, however, hub gear systems exist. For example, Vélib' and Vélo'v, the public bicycle rental programmes in Paris and Lyon, use bikes with 3-speed hub gears.
Unlike derailleur gears, where the gears and mechanism are exposed to the elements, hub gears and lubricants are sealed within the hub of the bicycle's rear wheel. Gears are changed by a cable which is tightened or loosened by a lever or twist grip on the handlebars.
By 1902 Reilly had designed a 3-speed hub gear. He parted company with the manufacturer of 'The Hub' but had signed away to them the intellectual rights to his future gear designs. To circumvent this problem, the patents for Reilly's 3-speed were obtained in the name of his colleague, James Archer. Meanwhile, well-known English journalist and inventor Henry Sturmey had also invented a 3-speed hub. In 1903 Frank Bowden, head of the Raleigh cycle company, formed The Three-Speed Gear Syndicate, having obtained the rights to both the Reilly/Archer and Sturmey 3-speeds. Reilly's hub went into production as the first Sturmey Archer 3-speed.
In 1902 Mikael Pedersen (who also produced the Dursley Pedersen bicycle) patented a 3-speed hub gear and this was produced in 1903. This was said to be based on the "counter shaft" principle but was arguably an unusual epicyclic gear, in which a second sun was used in place of an annulus.
By 1909 there were 14 different 3-speed hub gears on the British market.
By the 1930s hub gears were used on bicycles all over the world. They were particularly popular in the UK, The Netherlands, the German speaking countries and Scandinavia. Since the 1970s, they have become much less common in the English-speaking countries. But in many parts of northern Europe, where bicycles are regularly used as daily transport rather than merely for sport or leisure, hub gears are still widely used. Where they have become less popular it is because modern derailleur gears offer indexed shifting, a wider gear range and a more fashionable image for a lower price.
By 1987 Sturmey-Archer made only 3- and 5-speed hubs, and Fichtel & Sachs and Shimano made only 2- and 3-speed hubs. In that year the first book (apart from service manuals) for some 80 years dealing solely with epicyclic bicycle gears was published. Since then there has been a small but steady increase in interest in hub gears, reflected in the wider range of products now available. In 2008, Sturmey-Archer make 3-, 5- and 8-speed hubs, SRAM (successor to Fichtel & Sachs) make 3-, 5-, 7- and 9-speeds, Shimano make 3-, 7- and 8-speeds, and Rohloff make 14-speed hubs.
Though most hub gear systems use one rear sprocket, SRAM's DualDrive system combines an epicyclic hub with a multi-speed rear derailleur system to provide a wide-ranging drivetrain concentrated at the rear wheel. Brompton Bicycle have their own design, with a two-speed derailleur coupled to a three-speed SRAM hub gear. The system is useful for folding bicycles (where a multiple front chainset could foul the bike's folding mechanism) and in recumbent bicycles and freight bicycles (where small wheels and/or increased weight require a wider range of gears with smaller steps). Hub gears have in the past also been used on motorcycles, although this is now rare.