Bicycle chain
Overview
 
A bicycle chain is a roller chain
Roller chain
Roller chain or bush roller chain is the type of chain drive most commonly used for transmission of mechanical power on many kinds of domestic, industrial and agricultural machinery, including conveyors, wire and tube drawing machines, printing presses, cars, motorcycles, and simple machines like...

 that transfers power
Power (physics)
In physics, power is the rate at which energy is transferred, used, or transformed. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts—the more wattage, the more power, or equivalently the more electrical energy is used per unit...

 from the pedal
Bicycle pedal
A bicycle pedal is the part of a bicycle that the rider pushes with their foot to propel the bicycle. It provides the connection between the cyclist's foot or shoe and the crank allowing the leg to turn the bottom bracket spindle and propel the bicycle's wheels...

s to the drive-wheel
Bicycle wheel
A bicycle wheel is a wheel, most commonly a wire wheel, designed for bicycle. A pair is often called a wheelset, especially in the context of ready built "off the shelf" performance-oriented wheels....

 of a bicycle
Bicycle
A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

, thus propelling it. Most bicycle chains are made from plain carbon
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 or alloy steel, but some are nickel-plated to prevent rust, or simply for aesthetics. Nickel also confers a measure of self-lubrication to a chain's moving parts. Nickel is a relatively non-galling metal.
Obsolete chain designs previously used on bicycles included the block chain
Block chain
A block chain, also called a "bar-link" or "block-and-bar" chain, is a mechanical drive chain. It is composed of side plates, where each plate straddles one end of a block and is connected to the block with a pin going through a hole at one end of the block...

, the skip-link chain
Skip-link chain
Skip-link chain is an obsolete roller chain for bicycles in which side plates are alternately short and long, and so rollers are alternately close together and far apart....

, and the Simpson lever chain
Simpson Chain
The Simpson Chain or Simpson Lever Chain was an English-made bicycle chain invented by William Spears Simpson in 1895. The design departed from the standard roller bicycle chain: it was composed of linked triangles forming two levels. The inner level was driven by the chainring and the outer drove...

.
Encyclopedia
A bicycle chain is a roller chain
Roller chain
Roller chain or bush roller chain is the type of chain drive most commonly used for transmission of mechanical power on many kinds of domestic, industrial and agricultural machinery, including conveyors, wire and tube drawing machines, printing presses, cars, motorcycles, and simple machines like...

 that transfers power
Power (physics)
In physics, power is the rate at which energy is transferred, used, or transformed. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts—the more wattage, the more power, or equivalently the more electrical energy is used per unit...

 from the pedal
Bicycle pedal
A bicycle pedal is the part of a bicycle that the rider pushes with their foot to propel the bicycle. It provides the connection between the cyclist's foot or shoe and the crank allowing the leg to turn the bottom bracket spindle and propel the bicycle's wheels...

s to the drive-wheel
Bicycle wheel
A bicycle wheel is a wheel, most commonly a wire wheel, designed for bicycle. A pair is often called a wheelset, especially in the context of ready built "off the shelf" performance-oriented wheels....

 of a bicycle
Bicycle
A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

, thus propelling it. Most bicycle chains are made from plain carbon
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 or alloy steel, but some are nickel-plated to prevent rust, or simply for aesthetics. Nickel also confers a measure of self-lubrication to a chain's moving parts. Nickel is a relatively non-galling metal.

History

Obsolete chain designs previously used on bicycles included the block chain
Block chain
A block chain, also called a "bar-link" or "block-and-bar" chain, is a mechanical drive chain. It is composed of side plates, where each plate straddles one end of a block and is connected to the block with a pin going through a hole at one end of the block...

, the skip-link chain
Skip-link chain
Skip-link chain is an obsolete roller chain for bicycles in which side plates are alternately short and long, and so rollers are alternately close together and far apart....

, and the Simpson lever chain
Simpson Chain
The Simpson Chain or Simpson Lever Chain was an English-made bicycle chain invented by William Spears Simpson in 1895. The design departed from the standard roller bicycle chain: it was composed of linked triangles forming two levels. The inner level was driven by the chainring and the outer drove...

. Most modern bicycle chains used with a single chainring and single rear sprocket are conventional industrial bushing chain. Until the 1980s, most derailleur chains were also bushing chains, but today, virtually all derailleur chains are of the "Sedis" bushingless design. Compared to a bushing chain, a bushingless chain is cheaper to make, is less likely to break under shifting load, promotes better lubricant flow inside the rollers, and creates more lateral flexibility for multi-geared bicycles. However, it also wears much faster and has slightly worse mechanical efficiency than a bushing chain.

Before the safety bicycle
Safety bicycle
A safety bicycle is a type of bicycle that became very popular beginning in the late 1880s as an alternative to the penny-farthing or ordinary and is now the most common type of bicycle. Early bicycles of this style were known as safety bicycles because they were noted for, and marketed as, being...

, bicycles did not have chains and the pedals were typically attached directly to the drive-wheel, thus limiting top speed by the diameter of the wheel and resulting in designs with front wheels as large as possible. Various linkage mechanisms were invented to raise the effective gear ratio, but with limited success. Using chain drive allowed the mechanical advantage
Mechanical advantage
Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. Ideally, the device preserves the input power and simply trades off forces against movement to obtain a desired amplification in the output force...

 between the drive and driven sprocket
Sprocket
A sprocket or sprocket-wheel is a profiled wheel with teeth, cogs, or even sprockets that mesh with a chain, track or other perforated or indented material. The name 'sprocket' applies generally to any wheel upon which are radial projections that engage a chain passing over it...

s to determine the maximum speed, thereby enabling manufacturers to reduce the size of the driving wheel for safety. It also allowed for the development of variable gear
Gear
A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine....

ing, allowing cyclists to adjust their gearing
Bicycle gearing
A bicycle gear or gear ratio refers to the rate at which the rider's legs turn compared to the rate at which the wheels turn. Bicycle gearing refers to how the gear ratio is set or changed. On some bicycles, there is only one gear so the ratio is fixed. Most modern bicycles have multiple gears,...

 to the difficulty of the terrain, on the fly.

Efficiency

A bicycle chain
Roller chain
Roller chain or bush roller chain is the type of chain drive most commonly used for transmission of mechanical power on many kinds of domestic, industrial and agricultural machinery, including conveyors, wire and tube drawing machines, printing presses, cars, motorcycles, and simple machines like...

 can be very efficient: one study reported efficiencies as high as 98.6%. The study, performed in a clean laboratory environment, found that efficiency was not greatly affected by the state of lubrication. A larger sprocket will give a more efficient drive, reducing the movement angle of the links. Higher chain tension was found to be more efficient: "This is actually not in the direction you'd expect, based simply on friction".

Maintenance

How best to lubricate
Lubrication
Lubrication is the process, or technique employed to reduce wear of one or both surfaces in close proximity, and moving relative to each another, by interposing a substance called lubricant between the surfaces to carry or to help carry the load between the opposing surfaces. The interposed...

 a bicycle chain is a commonly debated question among cyclists. Liquid lubricants penetrate to the inside of the links and are not easily displaced, but quickly attract dirt. "Dry" lubricants, often containing wax
Wax
thumb|right|[[Cetyl palmitate]], a typical wax ester.Wax refers to a class of chemical compounds that are plastic near ambient temperatures. Characteristically, they melt above 45 °C to give a low viscosity liquid. Waxes are insoluble in water but soluble in organic, nonpolar solvents...

 or Teflon
Polytetrafluoroethylene
Polytetrafluoroethylene is a synthetic fluoropolymer of tetrafluoroethylene that finds numerous applications. PTFE is most well known by the DuPont brand name Teflon....

, are transported by an evaporating solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...

, and stay cleaner in use. The cardinal rule for long chain life is never to lubricate a dirty chain, as this washes abrasive particles into the rollers. Chains should be cleaned before lubrication. The chain should be wiped dry after the lubricant has had enough time to penetrate the links. An alternative approach is to change the (relatively cheap) chain very frequently; then proper care is less important. Some utility bicycle
Utility bicycle
A utility bicycle is a bicycle designed for practical transportation, as opposed to bicycles which are primarily designed for recreation and competition, such as touring bicycles, racing bicycles, sport/training bicycles, and mountain bicycles. The vast majority of bicycles can be found in the...

s have fully enclosing chain guard
Gear case
A gear case, also known as a chain case, is an enclosure for the bicycle chain and sprocket assemblages commonly employed by utility bicycles. It serves to protect the chain from mud and dirt and tends to fully enclose the drive train. It may also contain an oil bath to keep the chain lubricated....

s which virtually eliminate chain wear and maintenance. On recumbent bicycle
Recumbent bicycle
A recumbent bicycle is a bicycle that places the rider in a laid-back reclining position. Most recumbent riders choose this type of design for ergonomic reasons; the rider's weight is distributed comfortably over a larger area, supported by back and buttocks...

s the chain is often run through tubes to prevent it from picking up dirt, and to keep the cyclist's leg free from oil and dirt.

Removal

On most upright bicycles, the chain loops through the right rear triangle made by the right chain stay, right seat stay, and seat tube. Thus a chain must be separated, "broken" is a term commonly used, with a chain tool
Chain tool
400px|thumb|right|A typical chain tool. With a chain placed on the central sprocket, the screw is turned until a pin is pushed from the linkageA chain tool is a small mechanical device used to "break" a bicycle chain in such a way that it can be mended with the same tool. A bicycle chain has...

 or at a master link. (Care must be taken not to push the rivet all the way out, as it is very difficult to reinsert. See "Removing a Bicycle Chain" in the Wikibook on bicycles.) A master link
Master link
right|300px|thumb|Figure 3: A [[SRAM Corporation|SRAM]] Powerlink, joining two ends of a chain.A master link or quick-release link is a bicycle chain accessory that allows convenient removal and reconnection of an installed bicycle chain without the need for a chain tool. It acts as a set of the...

, also known as a connecting link, allows the chain to be inserted or removed with simpler tools, or even no tools, for cleaning or replacement.

Some newer chain designs, such as Shimano
Shimano
Shimano, Inc. is a Japanese multinational manufacturer of cycling components, fishing tackle, and rowing equipment.In 2005, the company had net sales of US $1.4 billion. Bicycle components provided 75% of its sales income...

 and Campagnolo
Campagnolo
Campagnolo is an Italian manufacturer of high-end bicycle components with headquarters in Vicenza, Italy. The components are organised as groupsets and are a near-complete collection of a bicycle's mechanical parts. Campagnolo's flagship components are the Super Record, Record, and Chorus...

 10-speed chains, require a special replacement pin to be used when installing or reinstalling a separated chain. An alternative to this process is to install a master link, such as a SRAM Power Link or a Wippermann Connex
Wippermann
Wippermann jr GmbH is a roller chain manufacturer located in Hagen, Germany, and they make the Connex brand of bicycle chains and master links. Their bicycle chains include such high-end features as nickel-plating, hollow pins, stainless steel, titanium rollers, and cutout plates. In 2008,...

.

Wear

Chain wear, or chain stretch, becomes an issue with extensive cycling. Although the overall effect is often called "stretch", chains generally wear through attrition of the bushings (or half-bushings, in the Sedis design) and not by elongation of the sideplates. The tension
Tension (mechanics)
In physics, tension is the magnitude of the pulling force exerted by a string, cable, chain, or similar object on another object. It is the opposite of compression. As tension is the magnitude of a force, it is measured in newtons and is always measured parallel to the string on which it applies...

 created by pedaling is insufficient to cause the latter. Because an old chain is longer than needed, its links will not precisely fit the spaces between teeth in the drivetrain
Bicycle drivetrain systems
Bicycle drivetrain systems are used to transmit power on bicycles, tricycles, quadracycles, unicycles, or other human-powered vehicles from the riders to the drive wheels. Most also include some type of a mechanism to convert speed and torque via gear ratios....

, making gear shifts a problem and possibly resulting in a 'skipping' chain that reduces power transfer and makes pedalling very uncomfortable.

Since chain wear is strongly aggravated by dirt getting into the links, the lifetime of a chain depends mostly on how well it is cleaned (and lubricated) and does not depend on the mechanical load. Therefore, well-groomed chains of heavily used racing bicycles will often last much longer than those of a lightly used, but not so well cleaned city bike. Depending on use and cleaning, a chain can last only 1,000 km (e.g. in cross-country use, or all-weather abuse), 3,000 to 5,000 km for well-maintained derailer chains, or more than 6,000 km for perfectly groomed high-quality chains, single-gear, or hub-gear chains (preferably with a full cover chain guard).

Chain wear rates are highly variable, so replacement by calendar is likely to cause either needless chain replacement or continued use of a worn chain, damaging rear sprockets. One way to measure wear is with a ruler. Another is with a chain wear tool, which typically has a "tooth" of about the same size found on a sprocket. They are simply placed on a chain under light load and report a "go/no-go" result - if the tooth drops in all the way, the chain should be replaced.

Twenty half-links in a new chain measure 10" (254 mm), and replacement is recommended before the old chain measures 256 mm (0.7% wear). A safer time to replace a chain is when 24 half-links in the old chain measure 121/16 inches (0.5% wear). If the chain has worn beyond this limit, the rear sprocket
Sprocket
A sprocket or sprocket-wheel is a profiled wheel with teeth, cogs, or even sprockets that mesh with a chain, track or other perforated or indented material. The name 'sprocket' applies generally to any wheel upon which are radial projections that engage a chain passing over it...

s are also likely to wear, in extreme cases followed by the front chainrings. In this case, the 'skipping' mentioned above is liable to continue even after the chain is replaced, as the teeth of the sprockets will have become unevenly worn (in extreme cases, hook-shaped). Replacing worn sprocket cassettes and chainrings after missing the chain replacement window is much more expensive than simply replacing a worn chain in the first place.

Sizes

The chain in use on modern bicycles has a 1/2" pitch, which is ANSI
Ansi
Ansi is a village in Kaarma Parish, Saare County, on the island of Saaremaa, Estonia....

 standard #40, where the 4 indicates the pitch of the chain in eighths of an inch, and metric #8, where the 8 indicates the pitch in sixteenths of an inch.

Width

Chains comes in either 3/32", 1/8", 5/32" or 3/16" roller widths: 5/32" is used on cargo bikes and trikes
Tricycle
A tricycle is a three-wheeled vehicle. While tricycles are often associated with the small three-wheeled vehicles used by pre-school-age children, they are also used by adults for a variety of purposes. In the United States and Canada, adult-sized tricycles are used primarily by older persons for...

, 1/8" with low-cost coaster brake (back pedal) bikes, hub gear
Hub gear
A hub gear, internal-gear hub, or just gear hub is a gear ratio changing system commonly used on bicycles that is implemented with planetary or epicyclic gears. The gears and lubricants are sealed within the hub-shell of the bicycle's rear wheel, as opposed to derailleur gears, where the gears and...

 and fixed gear bicycles, and on track bikes. (Fixed sprockets and freewheels are also available in 3/32" widths; fixed gear and single-speed
Single-speed bicycle
A single-speed bicycle is a type of bicycle with a single gear ratio. These bicycles are without derailleur gears, hub gearing or other methods for varying the gear ratio of the bicycle....

 bikes can be set up to use either 1/8" or 3/32" chains.) Derailleur equipped bikes such as racing
Racing bicycle
A racing bicycle, also known as a road bike, is a bicycle designed for competitive road cycling, a sport governed by according to the rules of the Union Cycliste Internationale...

, touring
Touring bicycle
A touring bicycle is a bicycle designed or modified to handle bicycle touring. To make the bikes sufficiently robust, comfortable and capable of carrying heavy loads, special features may include a long wheelbase , frame materials that favor flexibility over rigidity , heavy duty wheels , and...

 and mountain bike
Mountain bike
A mountain bike or mountain bicycle is a bicycle created for off-road cycling. This activity includes traversing of rocks and washouts, and steep declines,...

s use 3/32" chains exclusively.

The Wikibook, "Bicycle Maintenance and Repair", explains that the difference between derailleur chains commonly labelled 8-speed, 9-speed, and 10-speed is in its external width (all are 3/32" chains, that is, in their minimum internal clearances).

Length

New chains usually come in a stock length, long enough for most upright bike applications. The appropriate number of links must be removed before installation in order for the drive train to function properly. The pin connecting links can be pushed out with a chain tool
Chain tool
400px|thumb|right|A typical chain tool. With a chain placed on the central sprocket, the screw is turned until a pin is pushed from the linkageA chain tool is a small mechanical device used to "break" a bicycle chain in such a way that it can be mended with the same tool. A bicycle chain has...

 to shorten, and additional links may be added to lengthen.

In the case of derailleur gears
Derailleur gears
Derailleur gears are a variable-ratio transmission system commonly used on bicycles, consisting of a chain, multiple sprockets of different sizes, and a mechanism to move the chain from one sprocket to another...

 the chain is usually long enough so that it can be shifted onto the largest front chain ring and the largest rear sprocket without jamming, and not so long that, when shifted onto the smallest front chain ring and the smallest rear sprocket, the rear derailleur cannot take up all the slack. Meeting both these requirements is only possible if the rear derailleur is compatible with the gear range being used on the bike.

In the case of single-speed bicycle
Single-speed bicycle
A single-speed bicycle is a type of bicycle with a single gear ratio. These bicycles are without derailleur gears, hub gearing or other methods for varying the gear ratio of the bicycle....

s and hub gear
Hub gear
A hub gear, internal-gear hub, or just gear hub is a gear ratio changing system commonly used on bicycles that is implemented with planetary or epicyclic gears. The gears and lubricants are sealed within the hub-shell of the bicycle's rear wheel, as opposed to derailleur gears, where the gears and...

s, the chain length must match the distance between crank and rear hub and the sizes of the front chain ring and rear sprocket. These bikes usually have some mechanism for small adjustments such as horizontal dropouts
Dropout (bicycle part)
A bicycle dropout is a type of fork end that allows the rear wheel to be removed without first derailing the chain. The more inclusive term fork end refers to a slot in a frame or fork where the axle of the wheel is attached....

, track ends, or an eccentric mechanism
Eccentric (mechanism)
In mechanical engineering, an eccentric is a circular disk solidly fixed to a rotating axle with its centre offset from that of the axle ....

 in the rear hub or the bottom bracket
Bottom bracket
The bottom bracket on a bicycle connects the crankset to the bicycle and allows the crankset to rotate freely. It contains a spindle that the crankset attaches to, and the bearings that allow the spindle and cranks to rotate. The chainrings and pedals attach to the cranks...

. In extreme cases, a chain half-link may be necessary.

Variations

In order to reduce weight, chains have been manufactured with hollow pins and with cut-outs in the links. A few titanium chains have also been made, but while much lighter they are vastly more expensive, perhaps 10x the cost, and the titanium bearing surfaces reportedly wear quickly, leading to shortened life and reduced efficiency.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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