Modern bicycles use roller chain to connect the cranks to the rear wheel. Chain drives are among the most efficient means of power transmission known.
Chain size is specified by pitch and width. The pitch is the distance between rollers (1/2" on all modern bicycle chain). The width is nominally the width where the sprocket teeth fit in. Bicycle chain comes in four basic widths:
3/16" (.1875", 4.76 mm), used until the middle of the 20th century on many bicycles; this was inch-pitch chain.
1/8" (0.125", 3.18 mm) chain is used on most single-speed bicycles, and bicycles with internal gearing.
3/32" (0.094", 2.30 mm) chain is used on derailer equipped bicycles that have more than 3 cogs at the rear.
Even somewhat narrower chain, typically .090" or 2.29 mm between the inner plates, is used for derailer-equipped bicycles with 9 or more sprockets at the rear.
There is some confusion in these numbers because the actual width of a 1/8" sprocket is typically 1/8"(3.175 mm) and the gap between the inner side plates of the chain must be slightly wider to fit over the teeth. The width of the teeth on derailer-equipped bicycles with 5 or 6 rear sprockets was traditionally 2 mm, and the 3/32" (2.30 mm) chain would fit over those teeth -- but the smaller widths with larger number of sprockets are not as well standardized. Chains for derailer applications also come in various external widths. Newer clusters which have more sprockets also use chain with thinner side plates and with rivets whose ends are flush with the side plates.
In some triple-chainring installations, typically when the "granny" gear is unusually small, it may be impossible to get good shifting to the "granny" chainring with the normal derailer adjustments.
A loose adjustment of the low-gear stop causes the chain to derail past the small chainring, but a tighter setting results in slow downshifting to the small ring.
In such cases, a good, if inelegant, solution is sometimes to install a chain deflector, an anti-derailment device that clamps to the seat tube. These products, such as the 3rd Eye Chain Watcher ® and the N-Gear Jump Stop ® set up a barrier preventing the chain from overshooting the small ring, no matter how loose the low-gear stop is set. This allows the low-gear stop to be set to allow the derailer to move farther inboard for faster, more precise shifting, even under some load. These devices can often save the day when extra-wide range gearing is used on a mountain bike or tandem.
Any of several types of protective baffle used to prevent the chain from entrapping a trouser leg, or soiling the cyclist's leg or clothing. Getting a trouser leg caught in the chain can be an inconvenience on any bicycle, but, in the case of a bicycle with a coaster brake or a fixed gear, it can be extremely dangerous.
The traditional "hockey-stick" type chainguard extends from the seat stay forward and covers the upper run of chain, running down the front side of the chainwheel.
The full gear case or chain case completely encloses the chain and protects it from contamination. This type of chainguard is, unfortunately, not widely available in the U.S., though it is quite popular in the Netherlands.
Chainwheel discs, unlike the above styles of chainguard, are usable on bicycles with derailer gearing and multiple chainwheels. They are primarily intended to prevent soiled clothing, since the front derailer tends to keep trouser cuffs from being snagged. Unfortunately, many chainwheel discs interfere with obtaining the best possible front derailer adjustment. Should the chain become derailed on a bike with a chainwheel disc, it may become seriously wedged between the disc and the large chainring. Chainwheel discs are rarely found on high-quality bicycles.
Some bikes have a small brazed-on peg facing inward near the bottom of the right seat stay. This is intended to support the chain when the rear wheel has been removed for some reason. This is, in practice, a pretty useless feature.
This refers to how straight the chain runs between the front and rear sprockets. Ideally, both sprockets should be in the same plane, so that there is no sideward motion or stress to the chain. This constitutes "perfect chainline".
In the case of derailer geared bicycles, the chainline is not perfect in most gears. The worse the chainline, the worse the mechanical efficiency of the drive train.
"Correct" chainline for a derailer system is a matter of opinion, and depends on the intended use of the bicycle. There are two "simple" answers to the question of what constitutes proper chainline:
Chain suck occurs primarily when downshifting under load from the middle to the smallest chainring. The bottom run of the chain may not immediately disengage from the middle ring, and can get carried upward until it wedges betwixt the chainwheels and the right chainstay.
This jams the crankset. Since you probably wouldn't have been shifting to the granny if you weren't already climbing, the sudden lock-up of the drive train deprives you of what little momentum you had, and you are very likely to stall and fall.
Chain suck is commonly caused by bent chainring teeth, dirty chains, or, occasionally, burrs on the teeth of new chainwheels.
A device used to adjust the chain tension when a bike with vertical dropouts is converted to use a single-speed or internal-gear drive train. Some of these use two pulleys, like a rear derailer that doesn't move from side to side, others use a single pulley. If used with a front derailer, a chain tensioner must be spring-loaded like a rear derailer. A chain tensioner cannot be used with a fixed gear, though other solutions exist -- see my article on fixed-gear conversions.
A device used on some one-speed bicycles to adjust the chain tension by pulling back on the rear axle with a screw thread. One popular type used on BMX bicycles is called a "banjo bolt"
A tool used to press the rivet pin of a chain partway out of a link, in order to disconnect ("break") a chain to shorten it or to remove it from the bicycle.
A chain tool has traditionally also been used to insert a rivet pin to reassemble or lengthen a chain. Some narrow chains require replacement of a rivet pin instead, though many chains are equipped with a special link which can be disassembled and reassembled without pressing out a pin. For 1/8" inch wide chains, this is called the master link. The SRAM Power Link and similar products from Wippermann and KMC work with chains on derailer-equipped bicycles. With the narrowest chains, options become more limited.
A metal bar with a short length of bicycle chain attached to it, somewhat resembling a whip. This is used as a wrench to unscrew threaded sprockets, or to keep a freehub body from ratcheting backwards while the lock ring is being unscrewed.
If you don't have a chain whip, or if you are trying to remove a particularly stubborn threaded sprocket, you can substitute a short length of chain held in a vise:
Chamois is a type of leather made from sheep. It is very soft and supple. Traditional cycling shorts were lined with a pad of chamois leather for comfort.
Genuine chamois is expensive and requires extra care in washing and treatment to preserve it, so it is no longer in common use for cycling shorts. Most newer cycling shorts have artificial "chamois" made of specially woven cloth.
Raleigh trademark for a family of wheelie bikes. These have become moderately valuable to collectors.
In the 2005 model year, there was a fad for "retro choppers" These are not true wheelie bikes, but have styling similar to a "chopper" motorcycle. They'll generally feature extended forks with very slack angles and a very laid-back seat tube angle as well. The resulting riding position is midway between a conventional upright bike and a recumbent. Retro choppers usually have unusually wide rear tires, and medium width front tires. Choppers tend to be heavy, sluggish bikes, suitable for short leisurely rides in flat terrain.
Chromium is a metal, which is used in two ways in bicycle technology:
As an alloying element to steel, usually along with molybdenum or vanadium. It makes the steel tougher.
As a plating for steel or brass, it has a shiny silver appearance, and provides some protection against rust.
Practically all top-of-the-line racing bikes in the 1970s were equipped with Cinelli handlebars and stems.
Cinelli also pioneered plastic saddles for high end bikes, under the Unica name.
Cinelli was probably the first to offer "clipless" pedals, with the infamous Cinelli M71 "death cleats." These "step-in" pedals required the rider to reach down and manually release each pedal before unclipping was possible!