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Crankset
The crankset (in the US) or chainset (in the UK) is the component of a bicycle drivetrain that converts the reciprocating motion of the rider's legs into rotational motion used to drive the chain or belt, which in turn drives the rear wheel. It consists of one or more sprockets, also called chainrings or chainwheels, attached to the cranks, also called arms or crankarms, to which the pedals attach. It is connected to the rider by the pedals, to the bicycle frame by the bottom bracket, and to the rear sprocket, cassette, or freewheel via the chain.
The two cranks, one on each side and usually mounted 180° apart, connect the bottom bracket axle to the pedals.
Bicycle cranks can vary in length to accommodate different sized riders and different types of cycling. Crank length is measured from the center of the pedal spindle to the center of the bottom bracket spindle or axle. The larger bicycle component manufacturers typically offer crank lengths for adult riders from 165 to 180 mm (6.5 to 7.1 in) long in 2.5 mm (0.098 in) increments, with 170 mm (6.7 in) cranks being the most common size. A few small specialty manufacturers make bicycle cranks in a number of sizes smaller than 165 mm (6.5 in) and longer than 180 mm (7.1 in). Some manufacturers also make bicycle cranks that can be adjusted to different lengths.[citation needed]
While logic would suggest that, all other things being equal, riders with shorter legs should use proportionally shorter cranks and those with longer legs should use proportionally longer cranks, this is not universally accepted. However, very few scientific studies have definitively examined the effect of crank length on sustained cycling performance and the studies' results have been mixed. Bicycle crank length has not been easy to study scientifically for a number of reasons, chief among them being that cyclists are able to physiologically adapt to different crank lengths. Cyclists are typically more efficient pedalling cranks with which they have had an adaptation period. Several different formulas exist to calculate appropriate crank length for various riders. In addition to the rider's size, another factor affecting the selection of crank length is the rider's cycling specialty and the type of cycling event.
Historically, bicycle riders have typically chosen proportionally shorter cranks for higher cadence cycling such as criterium and track racing, while riders have chosen proportionally longer cranks for lower cadence cycling such as time trial racing and mountain biking. However, the evolution of very low rider torso positions to reduce aerodynamic drag for time trial racing and triathlon cycling can also affect crank selection for such events. Some have suggested that proportionally shorter cranks may have a slight advantage for a rider with a very low torso position and an acute hip angle, especially as the rider pedals near the top-dead-center position of the pedal stroke. Cranks can be shortened for medical reasons using shorteners such as Ortho Pedal.
Unicycle cranks vary in length to accommodate different unicycle wheel sizes, and different unicycling disciplines. As almost all unicycles are ungeared, crank length is a major factor in determining how much force is transmitted to the wheel. Larger wheel diameters, such as 660 to 910 mm (26 to 36 in), require longer cranks, as do disciplines such as Mountain Unicycling, Trials, Street, and Flatland. These unicycles and disciplines commonly use cranks lengths greater than 125 mm (4.9 in). For indoor unicycling such as freestyle or hockey, shorter cranks give a smoother pedaling motion and enable tighter turns without the pedal hitting the floor. Crank lengths of 100 mm (3.9 in) are common, although some riders use cranks as short as 79 mm (3.1 in). As there is no chainwheel on a unicycle, right and left cranks are identical, except for the pedal attachment thread in the left-hand crank, which is reverse threaded.
Cranks are constructed of either an aluminum alloy, titanium, carbon fiber, chromoly steel, or some less expensive steel. Tubular steel cranks (such as Tioga's Revolver) can be light and very strong, are usually found on BMX bikes, and are slowly finding their way to mountain bikes (dirt jumping and urban assault). Aluminum cranks may be cast, hot forged or cold forged ("cold" in this context means the billet from which the crank is to be made is heated to a specified temperature well below the melting point, not room temperature). Cold forging gives the metal additional strength, and the cranks can therefore be made lighter without increasing the risk of breakage. Shimano "Hollowtech" aluminum cranks are made by forging the main arms around a hard steel insert which is then withdrawn, leaving an internal void to save weight.[disputed – discuss][citation needed] They are then welded up before final machining.[disputed – discuss][citation needed]
There are a variety of methods used to attach the cranks to the bottom bracket spindle (or axle).
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Crankset
The crankset (in the US) or chainset (in the UK) is the component of a bicycle drivetrain that converts the reciprocating motion of the rider's legs into rotational motion used to drive the chain or belt, which in turn drives the rear wheel. It consists of one or more sprockets, also called chainrings or chainwheels, attached to the cranks, also called arms or crankarms, to which the pedals attach. It is connected to the rider by the pedals, to the bicycle frame by the bottom bracket, and to the rear sprocket, cassette, or freewheel via the chain.
The two cranks, one on each side and usually mounted 180° apart, connect the bottom bracket axle to the pedals.
Bicycle cranks can vary in length to accommodate different sized riders and different types of cycling. Crank length is measured from the center of the pedal spindle to the center of the bottom bracket spindle or axle. The larger bicycle component manufacturers typically offer crank lengths for adult riders from 165 to 180 mm (6.5 to 7.1 in) long in 2.5 mm (0.098 in) increments, with 170 mm (6.7 in) cranks being the most common size. A few small specialty manufacturers make bicycle cranks in a number of sizes smaller than 165 mm (6.5 in) and longer than 180 mm (7.1 in). Some manufacturers also make bicycle cranks that can be adjusted to different lengths.[citation needed]
While logic would suggest that, all other things being equal, riders with shorter legs should use proportionally shorter cranks and those with longer legs should use proportionally longer cranks, this is not universally accepted. However, very few scientific studies have definitively examined the effect of crank length on sustained cycling performance and the studies' results have been mixed. Bicycle crank length has not been easy to study scientifically for a number of reasons, chief among them being that cyclists are able to physiologically adapt to different crank lengths. Cyclists are typically more efficient pedalling cranks with which they have had an adaptation period. Several different formulas exist to calculate appropriate crank length for various riders. In addition to the rider's size, another factor affecting the selection of crank length is the rider's cycling specialty and the type of cycling event.
Historically, bicycle riders have typically chosen proportionally shorter cranks for higher cadence cycling such as criterium and track racing, while riders have chosen proportionally longer cranks for lower cadence cycling such as time trial racing and mountain biking. However, the evolution of very low rider torso positions to reduce aerodynamic drag for time trial racing and triathlon cycling can also affect crank selection for such events. Some have suggested that proportionally shorter cranks may have a slight advantage for a rider with a very low torso position and an acute hip angle, especially as the rider pedals near the top-dead-center position of the pedal stroke. Cranks can be shortened for medical reasons using shorteners such as Ortho Pedal.
Unicycle cranks vary in length to accommodate different unicycle wheel sizes, and different unicycling disciplines. As almost all unicycles are ungeared, crank length is a major factor in determining how much force is transmitted to the wheel. Larger wheel diameters, such as 660 to 910 mm (26 to 36 in), require longer cranks, as do disciplines such as Mountain Unicycling, Trials, Street, and Flatland. These unicycles and disciplines commonly use cranks lengths greater than 125 mm (4.9 in). For indoor unicycling such as freestyle or hockey, shorter cranks give a smoother pedaling motion and enable tighter turns without the pedal hitting the floor. Crank lengths of 100 mm (3.9 in) are common, although some riders use cranks as short as 79 mm (3.1 in). As there is no chainwheel on a unicycle, right and left cranks are identical, except for the pedal attachment thread in the left-hand crank, which is reverse threaded.
Cranks are constructed of either an aluminum alloy, titanium, carbon fiber, chromoly steel, or some less expensive steel. Tubular steel cranks (such as Tioga's Revolver) can be light and very strong, are usually found on BMX bikes, and are slowly finding their way to mountain bikes (dirt jumping and urban assault). Aluminum cranks may be cast, hot forged or cold forged ("cold" in this context means the billet from which the crank is to be made is heated to a specified temperature well below the melting point, not room temperature). Cold forging gives the metal additional strength, and the cranks can therefore be made lighter without increasing the risk of breakage. Shimano "Hollowtech" aluminum cranks are made by forging the main arms around a hard steel insert which is then withdrawn, leaving an internal void to save weight.[disputed – discuss][citation needed] They are then welded up before final machining.[disputed – discuss][citation needed]
There are a variety of methods used to attach the cranks to the bottom bracket spindle (or axle).