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Hub gears or internal-gear hubs are gear ratio changing systems commonly used on bicycles. Hub gear systems generally have a long and largely maintenance-free life though some are not suitable for high-stress use in competitions or hilly, off-road conditions.

Many commuter or urban cycles such as European city bikes are now commonly fitted with 7-speed gear-hubs and 8-speed systems are becoming increasingly available. Older or less costly utility bicycles often use 3-speed gear-hubs, e.g. the public bicycle rental programmes in Paris, Montreal, Lyon, London, and Washington, DC (Vélib', Bixi, Vélo'v, Barclays Cycle Hire, and Capital Bikeshare). Many folding bicycles use 3-speed gear-hubs. Modern developments with up to 14 gear ratios are available.

Gear-hubs use internal planetary or epicyclic gearing. Unlike derailleur gears, where the gears and mechanism are exposed to the elements, hub gears and lubricants are sealed within the hub-shell of the bicycle's rear wheel.

Changing the gear ratio was traditionally accomplished by a lever connected to the hub. Twist-grip style shifters have become general.

History

Before epicyclic gears were used in bicycle hubs, they were used on tricycles. Patents for epicyclic hubs date from the mid-1880s.^[1] The first patent for a compact epicyclic hub gear was granted in 1895 to the American machinist Seward Thomas Johnson of Noblesville, Indiana, U.S.A.^[2] This was a 2-speed but was not commercially successful.

In 1896 William Reilly of Salford, England patented a 2-speed hub which went into production in 1898 as 'The Hub'.^[3] It was a great success, remaining in production for a decade. It rapidly established the practicality of compact epicyclic hub gears.

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.^[4] Meanwhile, well-known English journalist and inventor Henry Sturmey had also invented a 3-speed hub.^[5] 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.^[6]

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^[7] but was arguably an unusual epicyclic gear, in which a second sun was used in place of an annulus.^[8] In 1904 the Fichtel & Sachs company (Germany, Schweinfurt) produced a hub gear under license to Wanderer, and by 1909 there were 14 different 3-speed hub gears on the British market.^[9]

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. The cheaper and stronger (but less reliable) derailleur system now started to appear and offer a wider gear range.

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.^[10] Since then there has been a slow but steady increase in interest in hub gears, reflected in the wider range of products now available. As of 2008, Sturmey-Archer makes 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 announced the introduction of an 11-speed model in February 2010,^[11] Rohloff offers the Rohloff Speedhub with 14 speeds (introduced in 1998), and NuVinci make ∞-speed (CVT) 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 special three-speed wide-ratio Sturmey-Archer hub, the "BWR" (Brompton Wide Ratio). 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.

Principle of operation

The simplest 3-speed hubs use a single planetary epicyclic gearset. The sun gear is mounted solidly to the axle and is thus fixed. In low gear, the sprocket drives the annulus, while the planet carrier drives the hub, giving a gear reduction. In mid gear, the annulus is connected to both the sprocket and hub, giving a direct drive. The planets cycle freely. In high gear, the sprocket is switched to drive the planets, while the annulus remains connected to the hub, giving an overdrive gear.

The hub axle of a hub-gear (unlike that of a derailleur system) must be securely braced against rotation. While anti-rotation washers between the dropout and axle nut have often proved adequate, better quality modern systems use a reaction arm affixed to the chain stay. Rear wheels with drum brakes (another feature of better quality commuter bicycles) require a reaction arm anyway.

Advantages

Hub-gear systems can change gear ratios when the rear wheel is stationary. This is a considerable advantage for commuter cycling with frequent stops at city junctions, but can also be valuable for mountain biking in rough terrain.
Hub-gear systems are simple to use for inexperienced riders, because there is only a single shifter to operate. Most derailleur systems in contrast have two shifters, and require some forethought to avoid problematic gear combinations.
Hub-gear systems do not have overlapping gear ratios.
The mechanism is sealed within the hub and bathed in a lubricant. This protects it from water and grit.
The single chainline allows for a full chain enclosure chain guard, so the chain is also protected from water and grit.
The single chainline does not require the chain to bend or twist. As a result, the chain can be constructed differently (parallel pins instead of barrel-shaped ones^[12]), which makes it last significantly longer.
The single external sprocket means that the wheel can be built with less dish making it stronger than a similar wheel dished to accomodate multiple sprockets.
Hub gears completely avoid the danger of collision with the spokes and wheel-collapse that derailleur systems can suffer.
Hub gears provide a means for shifting gear ratios on drivetrains incompatible with external deraileurs such as belt drives and shaft drives.

Disadvantages

Hub-gears are typically more expensive than derailleur systems.
Gear-hubs with a large number of speeds will tend to be less efficient than a properly lubricated and adjusted derailleur system in new condition. However, less sophisticated gear-hubs such as the 3-speed hub (with only a single epicyclic stage per high/low gear, and direct drive in second gear), when run-in and properly lubricated, can match the efficiency of similar quality derailleur systems, because the hub-gear chain runs in a straight line and does not run through the jockey wheels of a chain tensioner. In real-world conditions, the efficiency of derailleur gears is commonly much more seriously handicapped by poor lubrication and the mis-use of gears causing 'cross-chain' conditions.
Gear-hubs will tend to be heavier than equivalent derailleur systems, and the additional weight is concentrated at the back wheel. On rear-suspension bicycles in sporting use this unsprung weight will adversely affect traction and braking. This is an insignificant factor in street or commuter-cycle use when climbing kerbs and crossing pot-holes.
Gear-hubs are complex and virtually impossible for the ordinary rider to repair - most certainly not as a side-of-the-road procedure. However, failures generally give plenty of warning (unlike the situation with alternative systems) and repair may be an option.^[13]
Gear-hubs systems are generally incompatible with quick release mechanisms/skewer axles^[14], a particular handicap for sporting use.
The gear-hub is an integral part of the wheel and it is not possible to change the wheel without also changing the hub. In sporting use, this handicaps quick-changing a damaged wheel, or using different tires on multiple wheels.

Hub-gears in everyday use

A modern twist-style seven-speed indexed shifter uses the same bowden cable as the older lever.

Traditional hub gears are indexed at the shifter making operation dependent on correct cable tension (and lubrication thereof). In practice, gear-jumping and consequent internal damage are unusual except in high-mileage units. Modern hub gear-units incorporate the indexing in the unit itself and are therefore unaffected by shifting malfunctions caused in this way.
The Sturmey Archer and Fichtel & Sachs 'Torpedo' systems defaulted to top gear at slack-cable, which could make the bicycle usable for long distance travel in flat terrain even if a fault developed in the change mechanism (rather like a derailleur system, which can be manually set to a high gear in case of a similar fault). Some modern hub gear systems (eg 7-speed Shimano) default to bottom gear and are thus more dependent on the (generally) very reliable cable-pull.

Hybrid gearing with derailleurs

It is often possible to combine internally-geared hubs with derailleurs. Any freewheeling hub with a sprocket suitable for narrow chain can be used with a double or triple crankset and front derailleur, in order to give a wider range and closer gear spacing. In this case a chain tensioner (or a rear derailleur fixed in one position) is needed to take up the slack, and care is needed not to over-torque the hub by using too small a chain ring/sprocket ratio. Alternatively, some hubs are capable of accepting two dished drive sprockets which can be shifted between using a rear derailleur. With careful sprocket selection, the gears of one sprocket fall half-way between those of the other, giving half-step gearing. This concept is used and extended in SRAM's 'dualdrive' system. When both front and rear derailleurs are used with a geared hub, the result is a very wide-ranging drivetrain, at the expense of increased weight and complexity.

Latest developments

Rohloff 14 speed internally-geared rear hub

Hubs with higher numbers of gears use multiple epicyclic gears driven by each other, their ratios chosen to give evenly spaced gears. The operating principle is the same. An exception is the older style of Sturmey-Archer 5-speed, which used a second shift lever to change between close and wide-range sun gears, effectively giving two 3-speed hubs in one unit. The middle gear in both ranges was direct drive, so there were 5 distinct gears.

The latest 14-ratio hub-gear systems have a 5 to 1 range and are now directly comparable to "27-speed" derailleur systems, since the latter have 3 overlapping ranges with no more than about 15 distinct gears. The hub-gear system is much easier and more intuitive to operate while suffering little from loss of mechanical efficiency.

Manufacturers

Bendix - From 1950s to 1970s, produced the two-speed "Kickback" hub
Rohloff
Shimano
SRAM
Sturmey-Archer
Fichtel & Sachs
Schlumpf

References

^ Berto, Frank (2009). The Dancing Chain : history and development of the derailleur bicycle, Third Edition. San Francisco, CA, USA: Van der Plas Publications/Cycle Publications. p. 34. ISBN 1892495414. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
^ Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.18-19
^ Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.19-22
^ Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.26-29
^ Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.31-34
^ Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.35-38
^ Evans, David E. The Ingenious Mr Pedersen, Alan Sutton, Stroud, 1992, p.49
^ Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.65
^ Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.67-68
^ Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987.
^ dave_atkinson (2010-02-05). "Shimano announce Alfine 11 speed | road.cc | The website for pedal powered people: Road cycling, commuting, leisure cycling and racing. Voted the UK's number 1 cycling website at the 2010 BikeBiz awards". road.cc. Retrieved 2010-12-14.
^ "Hub gears - chains". Hubgear.net. Retrieved 2010-12-14.
^ "Hub Stripping Tips! « Hubstripping.com". Hubstripping.wordpress.com. Retrieved 2010-12-14.
^ Sheldon Brown. "Internal-Gear Hubs". Retrieved 2010-12-12.

External links

[1] Berto, Frank (2009). The Dancing Chain : history and development of the derailleur bicycle, Third Edition. San Francisco, CA, USA: Van der Plas Publications/Cycle Publications. p. 34. ISBN 1892495414. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

[2] Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.18-19

[3] Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.19-22

[4] Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.26-29

[5] Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.31-34

[6] Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.35-38

[7] Evans, David E. The Ingenious Mr Pedersen, Alan Sutton, Stroud, 1992, p.49

[8] Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.65

[9] Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.67-68

[10] Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987.

[11] ve_atkinson (2010-02-05). "Shimano announce Alfine 11 speed | road.cc | The website for pedal powered people: Road cycling, commuting, leisure cycling and racing. Voted the UK's number 1 cycling website at the 2010 BikeBiz awards". road.cc. Retrieved 2010-12-14.

[12] "Hub gears - chains". Hubgear.net. Retrieved 2010-12-14.

[13] "Hub Stripping Tips! « Hubstripping.com". Hubstripping.wordpress.com. Retrieved 2010-12-14.

[brown-14] Sheldon Brown. "Internal-Gear Hubs". Retrieved 2010-12-12.

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@@ Line 1: / Line 1: @@
 {{transmission types}}
-[[Image:Rohloff-nabe.jpg|right|thumb|A chain-driven bicycle with a Rohloff 14 speed internally-geared rear hub]]
-[[Image:Epicyclic gear small.png|thumb|In this simple epicyclic gear mechanism, the inner gear or "sun gear" (green) provides the input rotation. The two "planet gears" (blue) rotate freely about the planet gear carrier (yellow) which is fixed. As the planet gears rotate about the sun gear, they propel the outer ring gear or "annulus" (red), which provides the output rotation]]
-[[File:Belt-drive internal-geared multi-speed rear hub.JPG|thumb|right|[[Belt-driven bicycle|Belt-drive]] internal-geared multi-speed rear [[Bicycle wheel#Hub shell|hub]] on a [[Trek Bicycle Corporation|Trek]] Soho]]
-[[Image:Speed1c.png|thumb|right|14-speed hub cutaway diagram]]
-[[Image:Three speed shifter.JPG|right|thumb|A 3-speed shifter on a [[Triumph Cycle Co. Ltd.|Triumph]].]]
-[[Image:Schaltgriff-sram-7.jpg|right|thumb|A twist-style seven-speed indexed shifter made by [[SRAM (bicycles)|SRAM]]]]
 '''Hub gears''' or '''internal-gear hubs''' are [[Bicycle gearing|gear ratio]] changing systems commonly used on [[bicycle]]s. Hub gear systems generally have a long and largely maintenance-free life though some are not suitable for high-stress use in competitions or hilly, off-road conditions.
-Many commuter or urban cycles such as [[European city bike]]s commonly have 7-speed gear-hubs with 8-speed systems becoming increasingly available.  Older or less costly [[utility bicycle]]s often use 3-speed gear-hubs, e.g. the public bicycle rental programmes in [[Paris]], [[Montreal]], [[Lyon]], [[London]], and [[Washington, DC]] ([[Vélib']], [[Bixi]], [[Vélo'v]], [[Barclays Cycle Hire]], and [[Capital Bikeshare]]). Many [[folding bicycles]] use 3-speed gear-hubs. Hubs with up to 14 gear ratios are available.
+Many commuter or urban cycles such as [[European city bike]]s are now commonly fitted with 7-speed gear-hubs and 8-speed systems are becoming increasingly available.  Older or less costly [[utility bicycle]]s often use 3-speed gear-hubs, e.g. the public bicycle rental programmes in [[Paris]], [[Montreal]], [[Lyon]], [[London]], and [[Washington, DC]] ([[Vélib']], [[Bixi]], [[Vélo'v]], [[Barclays Cycle Hire]], and [[Capital Bikeshare]]). Many [[folding bicycles]] use 3-speed gear-hubs. Modern developments with up to 14 gear ratios are available.
 Gear-hubs use internal planetary or [[epicyclic gearing]]. Unlike [[derailleur gear]]s, where the gears and mechanism are exposed to the elements, hub gears and lubricants are sealed within the hub-shell of the bicycle's rear wheel.
-Changing the gear ratio has traditionally accomplished by a lever connected to the hub via a [[Bowden cable]].  Twist-grip style [[Shifter (bicycle part)|shifters]] are also becoming popular.
+Changing the gear ratio was traditionally accomplished by a lever connected to the hub.  Twist-grip style [[Shifter (bicycle part)|shifters]] have become general.
 ==History==
+[[Image:Epicyclic gear small.png|thumb|In this simple epicyclic gear mechanism, the inner gear or "sun gear" (green) provides the input rotation. The two "planet gears" (blue) rotate freely about the planet gear carrier (yellow) which is fixed. As the planet gears rotate about the sun gear, they propel the outer ring gear or "annulus" (red), which provides the output rotation]]
 Before epicyclic gears were used in bicycle hubs, they were used on tricycles.   Patents for epicyclic hubs date from the mid-1880s.<ref>{{cite book  | last =  Berto   | first = Frank   | authorlink =   | coauthors = Tony Hadland, Jan Heine, Raymond Henry, Gordon Selby, Ron Shepherd, Walter Ulreich  | title = The Dancing Chain : history and development of the derailleur bicycle, Third Edition  | publisher = Van der Plas Publications/Cycle Publications  | year = 2009  | location = San Francisco, CA, USA  | page = 34  | url = http://www.cyclepublishing.com/cyclingbooks/dc.html  | isbn = 1892495414}}</ref> The first patent for a compact epicyclic hub gear was granted in 1895 to the American machinist Seward Thomas Johnson of Noblesville, Indiana, U.S.A.<ref>Hadland, Tony, ''The Sturmey-Archer Story'', Pinkerton Press, Birmingham, 1987, pp.18-19</ref> This was a 2-speed but was not commercially successful.
@@ Line 33: / Line 25: @@
 ==Principle of operation==
 The simplest 3-speed hubs use a single planetary epicyclic gearset. The sun gear is mounted solidly to the axle and is thus fixed. In low gear, the sprocket drives the annulus, while the planet carrier drives the hub, giving a gear reduction. In mid gear, the annulus is connected to both the sprocket and hub, giving a direct drive. The planets cycle freely. In high gear, the sprocket is switched to drive the planets, while the annulus remains connected to the hub, giving an overdrive gear.
-Hubs with higher numbers of gears use multiple epicyclic gears driven by each other, their ratios chosen to give evenly spaced gears. The operating principle is the same. An exception is the older style of Sturmey-Archer 5-speed, which used a second shift lever to change between close and wide-range sun gears, effectively giving two 3-speed hubs in one unit. The middle gear in both ranges was direct drive, so there were 5 distinct gears.
 The hub axle of a hub-gear (unlike that of a derailleur system) must be securely braced against rotation. While anti-rotation washers between the dropout and axle nut have often proved adequate, better quality modern systems use a reaction arm affixed to the chain stay. Rear wheels with drum brakes (another feature of better quality commuter bicycles) require a reaction arm anyway.
 ==Advantages==
+[[File:Belt-drive internal-geared multi-speed rear hub.JPG|thumb|right|Prototype [[belt-driven bicycle|belt-drive]] on a [[Trek Bicycle Corporation|Trek]] Soho is fitted with a sprocket too.]]
-* Hub-gear systems can change gear ratios when the rear wheel is stationary. This can be useful in [[urban cycling]] with frequent stops and [[mountain biking]] in rough terrain.
+* Hub-gear systems can change gear ratios when the rear wheel is stationary. This is a considerable advantage for [[urban cycling|commuter cycling]] with frequent stops at city junctions, but can also be valuable for [[mountain biking]] in rough terrain.
-* Hub-gear systems are simple to use for inexperienced riders, because there is only a single shifter to operate. Most derailleur systems in contrast have two shifters, and require some knowledge to avoid problematic gear combinations.
-* Hub-gear systems do not have overlapping gear ratios. For instance, the latest 14-ratio hub-gear systems have a 5 to 1 range comparable to a "27-speed" derailleur system, but the latter has 3 overlapping ranges with only about 14 to 15 distinct gears.
+* Hub-gear systems are simple to use for inexperienced riders, because there is only a single shifter to operate. Most derailleur systems in contrast have two shifters, and require some forethought to avoid problematic gear combinations.
+* Hub-gear systems do not have overlapping gear ratios.
 * The mechanism is sealed within the hub and bathed in a lubricant. This protects it from water and grit.
 * The single [[chainline]] allows for a full chain enclosure [[chain guard]], so the chain is also protected from water and grit.
 * The single chainline does not require the [[Bicycle chain|chain]] to bend or twist. As a result, the chain can be constructed differently (parallel pins instead of barrel-shaped ones<ref>{{cite web|url=http://www.hubgear.net/chains.html |title=Hub gears - chains |publisher=Hubgear.net |date= |accessdate=2010-12-14}}</ref>), which makes it last significantly longer.
 * The single external sprocket means that the wheel can be built with less [[Bicycle wheel#Dish|dish]] making it stronger than a similar wheel dished to accomodate multiple sprockets.
+* Hub gears completely avoid the danger of collision with the spokes and wheel-collapse that derailleur systems can suffer.
 * Hub gears provide a means for shifting gear ratios on [[Bicycle drivetrain systems|drivetrains]] incompatible with external deraileurs such as [[Belt-driven bicycle|belt drives]] and [[Shaft-driven bicycle|shaft drives]].
-* Hub gears cannot collide with the spokes and damage them.
 ==Disadvantages==
 *Hub-gears are typically more expensive than derailleur systems.
@@ Line 58: / Line 47: @@
 ==Hub-gears in everyday use==
+[[Image:Three speed shifter.JPG|left|thumb|Traditional lever change, 3-speed.]]
+[[Image:Schaltgriff-sram-7.jpg|right|thumb|A modern twist-style seven-speed indexed shifter uses the same [[bowden cable]] as the older lever.]]
 *Traditional hub gears are indexed at the shifter making operation dependent on correct cable tension (and lubrication thereof). In practice, gear-jumping and consequent internal damage are unusual except in high-mileage units. Modern hub gear-units incorporate the indexing in the unit itself and are therefore unaffected by shifting malfunctions caused in this way.
-*The [[Sturmey Archer]] and [[ZF Sachs|Fichtel & Sachs]] 'Torpedo' systems defaulted to top gear at slack-cable, which could make the bicycle usable for long distance travel in flat terrain even if a fault developed in the change mechanism (rather like a derailleur system, which can be manually set to a high gear in case of a similar fault). Some modern hub gear systems (eg 7-speed Shimano) default to bottom gear and are thus more dependent on the (generally) very reliable cable-pull.
+*The [[Sturmey Archer]] and [[ZF Sachs|Fichtel & Sachs]] 'Torpedo' systems defaulted to top gear at slack-cable, which could make the bicycle usable for long distance travel in flat terrain even if a fault developed in the change mechanism (rather like a derailleur system, which can be manually set to a high gear in case of a similar fault). Some modern hub gear systems (eg 7-speed Shimano) default to bottom gear and are thus more dependent on the (generally) very reliable cable-pull.{{-}}
 ==Hybrid gearing with derailleurs==
-It is often possible to combine internally-geared hubs with derailleurs. Any freewheeling hub with a sprocket suitable for narrow chain can be used with a double or triple crankset and front derailleur, in order to give a wider range and closer gear spacing. In this case a chain tensioner (or a rear derailleur fixed in one position) is needed to take up the slack, and care is needed not to over-torque the hub by using too small a chain ring/sprocket ratio. Alternatively, some hubs are capable of accepting two dished drive sprockets which can be shifted between using a rear derailleur. With careful sprocket selection, the gears of one sprocket fall half-way between those of the other, giving half-step gearing. This concept is used and extended in SRAM's 'dualdrive' system. When both front and rear derailleurs are used with a geared hub, the result is a very wide-ranging drivetrain, at the expense of increased weight and complexity.
+It is often possible to combine internally-geared hubs with derailleurs. Any freewheeling hub with a sprocket suitable for narrow chain can be used with a double or triple crankset and front derailleur, in order to give a wider range and closer gear spacing. In this case a chain tensioner (or a rear derailleur fixed in one position) is needed to take up the slack, and care is needed not to over-torque the hub by using too small a chain ring/sprocket ratio. Alternatively, some hubs are capable of accepting two dished drive sprockets which can be shifted between using a rear derailleur. With careful sprocket selection, the gears of one sprocket fall half-way between those of the other, giving half-step gearing. This concept is used and extended in SRAM's 'dualdrive' system. When both front and rear derailleurs are used with a geared hub, the result is a very wide-ranging drivetrain, at the expense of increased weight and complexity.{{-}}
+==Latest developments==
+[[Image:Speed1c.png|thumb|left|14-speed hub cutaway diagram]]
+[[Image:Rohloff-nabe.jpg|right|thumb|Rohloff 14 speed internally-geared rear hub]]
+Hubs with higher numbers of gears use multiple epicyclic gears driven by each other, their ratios chosen to give evenly spaced gears. The operating principle is the same. An exception is the older style of Sturmey-Archer 5-speed, which used a second shift lever to change between close and wide-range sun gears, effectively giving two 3-speed hubs in one unit. The middle gear in both ranges was direct drive, so there were 5 distinct gears.
+The latest 14-ratio hub-gear systems have a 5 to 1 range and are now directly comparable to "27-speed" derailleur systems, since the latter have 3 overlapping ranges with no more than about 15 distinct gears. The hub-gear system is much easier and more intuitive to operate while suffering little from loss of mechanical efficiency.{{-}}
 ==See also==
 * [[Bicycle gearing]]