Bicycle.

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Bicycle.
I

INTRODUCTION

Bicycle, vehicle usually consisting of two wheels fixed to a frame, steered by handlebars, and propelled by an arrangement of pedals and gears that are driven by the
feet. Different types of bicycle are tailored for different kinds of riding. The term bicycle is sometimes extended to include rider-propelled three-wheeled tricycles, which
are favored by young children and others, such as some senior citizens, who lack the balance needed to operate a two-wheeled bicycle.
Bicycles were immensely popular in Europe and the United States in the late 19th and early 20th centuries. Their popularity declined with the rise of the automobile and
the motorcycle, and bicycle manufacturers concentrated on producing bicycles for children. In the late 20th century, however, bicycles enjoyed a strong renaissance in
the United States. The energy crisis of the 1970s, the growing popularity of mountain bikes since the 1980s, general interest in aerobic exercise and fitness, the growth
of bicycle touring and fundraising events, and the success of American racing cyclists in international racing competitions all contributed to this renaissance.

II

TYPES OF BICYCLES

All bicycles fall into one of six general categories: touring, mountain, hybrid (sometimes called cross), utility, racing, or specialty. Components on each type are specially
selected to suit the uses for which the bicycle is designed.

A

Touring Bicycles

Touring bicycles are designed for riding on relatively smooth pavement. They are used for carrying panniers (saddlebags with an interior frame) and equipment over
long distances, and for some commuting and recreational riding. Touring bicycles are generally made with lightweight chromium-molybdenum (chromoly) steel,
aluminum, or composite frames that are designed for maximum strength and comfort. They commonly weigh between 9 and 11 kg (20 and 25 lb) and have a mediumlength wheelbase (distance between the front and back wheel hubs) for stability. Handlebars on touring bicycles may be dropped or upright. Wheels usually have
aluminum alloy rims, relatively heavy-gauge (thick) spokes to resist breaking under the extra weight of a load, and medium-width tires for secure handling and
puncture resistance. Saddles may be of any design comfortable to the individual rider. Touring bicycles are usually equipped with toe clips and cleats or clipless pedals
to maximize the rider's hill-climbing force. They commonly have triple chain rings and 21 to 27 speeds with gear ratios low enough to enable riders to pedal up
mountains even while carrying clothes and camping equipment. The frames of touring bicycles commonly come equipped with fittings for two or three water bottles and
for a tire pump, and with dropouts (strong metal tabs perforated with a threaded hole) near the front and rear hubs that can hold racks for carrying panniers filled with
clothes and other equipment for the tour.

B

Mountain Bikes

Mountain bikes are designed for off-road riding, including climbing and descending steep inclines over rough terrain. The mountain bike, which took the entire bicycling
industry by storm in the 1980s, introduced a whole new bicycle market as well as new competitive racing and touring events. Although initially the frames of mountain
bicycles were designed with a touring geometry, by the late 1980s a sprightlier-handling racing geometry began to dominate the market. The frame of a mountain
bicycle is usually somewhat smaller than a touring bicycle frame would be for the same rider. Like touring bicycles, mountain bikes usually have triple chain rings and 21
to 27 speeds with an emphasis on low gears. Mountain bikes also have cantilever brakes for increased breaking capacity. The wheels of mountain bikes may be
exceptionally wide and the tires may have deep, knobby tread and use low pressures to increase their grip on uneven rocks and obstacles.

C

Hybrid or Cross Bikes

In the late 1980s manufacturers realized that bicycles combining the features of both mountain bikes (notably cantilever brakes and frame geometry) and touring bikes
(notably medium-width, medium-pressure tires and provision for racks) were enormously popular among recreational, commuting, and touring cyclists. Typically, such a
hybrid, or cross, bike has either drop or flat handlebars and triple chain ring gearing. Many cyclists find the hybrid bike an ideal all-purpose bicycle for either road or
light off-road riding, as it has both the sure handling of the mountain bike on dirt and gravel and the lighter weight and lower rolling resistance of a road bike on
pavement. Sometimes hybrid bicycles are sold as commuter or city bicycles.

D

Utility Bicycles

Utility bicycles are commonly single-speed, three-speed, or five-speed machines, although automatic gear transmissions have also begun to appear on some models.
This category also includes some children's bicycles. A utility bicycle commonly weighs more than 14 kg (30 lb); has a long frame with large rakes, or bends, in the front
fork (two-pronged extension of the frame that attaches to the hub of the front wheel) for a soft ride; internal gearing, if any; upright or flat handlebars; and durable,
wide tires. Utility bikes may also have a chain guard to keep legs and pants from catching in the chain and coaster brakes that engage by rotating the pedals backward.
The saddles are often wide, have coiled springs, and are made of padded vinyl. Utility bicycles are generally inexpensive, are comfortable to ride for short distances, and
require relatively little maintenance. They are commonly used as rental bicycles (especially at resorts where people may ride on the beach) and as transportation in
developing countries throughout the world. In the first half of the 20th century, utility bicycles were found to be useful in warfare because they could go most places a
horse could but required less maintenance and no food.

E

Racing Bicycles

Racing bicycles are the lightest bicycles made and are available in forms designed either for racing on paved roads or on specially built tracks. Road-racing bicycles vary
in weight depending on the materials used, but they generally weigh about 8 kg (18 lb); track-racing bicycles, which are stripped of brakes, gears, and other
expendable parts, may weigh as little as 6 kg (13 lb).
Racing bicycles are optimized to minimize weight, reduce air resistance and friction with the ground, and provide greater control than other types of bicycles allow. They
are constructed using lightweight metal alloys and other materials. Components such as brake levers and chain rings are perforated to reduce weight whenever the
extra material can be safely removed without affecting the structural integrity of the component. A short wheelbase and small fork rakes produce a harsh ride but
increase responsiveness and maneuverability. Gear ratios are narrowly spaced and higher than average to give maximum speed and power; 16 to 18 speeds is most
common. Racing handlebars are usually narrow for minimum weight and wind resistance and dropped for maximum control and to allow numerous hand positions. In
certain track events or road time trials, the handlebars may also include an aerobar on which the rider may rest the forearms while maintaining an aerodynamic crouch
(aerobars are normally not allowed in mass-start races). Wheels have very narrow, light alloy rims and high-pressure tires to minimize friction and maximize responsive
handling. Wheels may have light-gauge (thin) spokes or may be of a special aerodynamic design to minimize wind resistance and turbulence. The saddle is usually as

narrow as possible to minimize weight and interference with pedaling.

F

Specialty Bicycles

Many other types of bicycles are designed for special purposes. Although not as common as standard single-rider racing, touring, mountain, or recreational bicycles,
they nonetheless have significant niches.
Recumbent bicycles are bicycles on which the rider sits upright as if in a chair, with legs and feet stretched out in front. Because they support the rider's lower back,
recumbents allow the rider far more leverage with the thigh muscles. They also have a lower center of gravity. The popularity of recumbents, especially for touring,
began increasing in the 1980s.
Tandems are bicycles built to carry two or more riders. The traditional "bicycle built for two" is operated by a captain, or front rider, who controls the steering and the
brakes, and by a stoker, or rear rider. The drive train is designed so that both riders may contribute to the pedaling. Tandems are seen in racing as well as in touring
and recreational riding, as two riders pedaling in cadence have far faster times than individual riders. Tandems are also useful for introducing visually impaired
individuals to bicycling or for touring with children not yet skilled enough to operate a standard bicycle. In these cases, the sighted cyclist or the parent rides as captain.
Agile bicycle-motocross (BMX) bicycles, modeled after the motocross "dirt-bike" motorcycle, are most popular with children and teenagers. BMX wheels are much smaller
in diameter than touring or hybrid wheels, and the frame is designed to be very small in relation to the size of the rider.
Freestyle stunt bicycles, which are BMX-style bicycles with a particularly strong frame and handlebars that can spin completely around without being stopped by gear or
brake cables, created a whole new sport of freestyling, or bicycle acrobatics. Their design enables riders to maneuver the bicycle by standing on foot pegs that extend
from the rear hub, as well as to jump themselves and the bike to great heights and even perform airborne somersaults by throwing their bodies and pulling sharply on
the handlebars. Freestyling reached its heyday in the 1980s but is still a feature at special meets.
Collapsible bicycles are useful for commuting and meeting size regulations on public transportation, including airlines. Alexander Moulton in England pioneered the smallwheeled foldable frame in 1962, and by the mid-1990s developers had produced a number of ingenious designs. Some, such as the Montague, are full-sized bicycles
that fold. Others, such as the Bike Friday, the Moulton, and the Swift Folder, have very small wheels.

III

COMPONENTS OF THE BICYCLE

The basic equipment on a bicycle includes a lightweight frame of thin tubing; wheels (usually spoked) with inflatable tires; an adjustable saddle or seat; brakes for
stopping; handlebars for balance and steering; and a drive train, usually consisting of a continuous chain driven by foot pedals, for propelling the bicycle. The bicycle
also may have gears for easy operation against strong winds and up hills, a suspension system for cushioning against bumps (particularly over off-road terrain), and
various accessories for safety and comfort.

A

Frame

Standard single-rider bicycles have two common frame designs: the diamond and the step-through. The more common diamond frame is named for the diamond shape
created by its front and rear triangles. The front triangle consists of the top tube between the headset (where the front fork and handlebars attach to the frame) and
the saddle, the down tube between the headset and the bottom bracket (where the pedals attach to the frame), and the seat tube between the saddle and the bottom
bracket. Two divergent rear triangles, one on each side of the rear wheel, share as one side the seat tube. Their other two sides are the seatstays (between the saddle
and the left and right sides of the rear hub) and the chainstays (between the bottom bracket and the left and right sides of the rear hub).
Bicycle frames come in a variety of sizes, which are based on the length of the seat tube. Standard bicycles for adults normally range from 31 to 65 cm (12 to 26 in);
smaller or larger sizes can also be custom-built. The frame of a road bicycle is considered to fit when the rider, with both feet placed flat on the ground, can stand
astride the top tube with about 3 cm (1 in) of clearance to the crotch. A mountain bicycle frame is usually fit to have 8 cm (3 in) or more of clearance.
Since the 1970s most women, as well as men, have ridden bicycles with a diamond frame, which used to be called the men's frame. The old-style V-shaped women's
frame, which had no top tube, is no longer manufactured because of the structural weakness inherent in the absence of one arm of the front triangle. Some women and
girls prefer a step-through frame over a diamond frame. In the step-through frame, the top tube may be lower and slant downward to the rear or it may be replaced
by two thinner tubes that are parallel and slant downward from the handlebars all the way to the rear hub (a design known as the mixte). Both designs preserve much
of the strength and rigidity of the traditional diamond frame.
The most desirable bicycle frames are both very strong and very lightweight. Frame tubes on the cheapest bicycles are made of carbon steel, which is relatively heavy.
On moderately priced bicycles, the tubes are thin-walled and made of lighter, high-tensile alloys such as chromoly steel and molybdenum-manganese steel. On
somewhat more expensive bicycles, tubes may be made of even lighter aluminum alloys. Aluminum is not as strong as steel, however, so aluminum-alloy tubing must
have a larger diameter and sometimes an oval cross section to offer the same strength that the steel alloys provide. Some of the most expensive super-lightweight
bicycle frames, usually for racing, are die-cast in one piece (known as a monocoque frame) out of carbon-fiber-epoxy composites or magnesium alloy. The lightest
racing bikes of all are made of titanium-steel or titanium-aluminum alloy tubing, which may weigh half of what stainless and other alloy steels weigh.

B

Wheels and Tires

Although there are many special wheels designed to reduce weight and wind resistance, most bicycle wheels consist of a circular rim attached to both sides of a central
hub by wire spokes under tension. The spokes usually hook into the edge of the hub at an angle rather than perpendicularly in order to convey the tangential force
from pedaling most efficiently from hub to rim. Spokes are also usually laced over and under one another to maintain their tension and to reduce their tendency to
loosen. Keeping the spokes under tension allows the bicycle wheel to be exceptionally strong while also exceptionally lightweight. This combination of benefits lasts only
as long as the rim is both radially true (perfectly circular) and laterally true (in one plane), however. If a spoke loosens or breaks, the balance of tensions among the
remaining spokes is thrown off, and further riding will rapidly cause the rim to become distorted or even irreparably bent into a characteristic potato-chip shape.
A circular rubber tire lined with an airtight inner tube (commonly made of latex or butyl) surrounds the rim. The inner tube is filled with air at a designated pressure.
Most bicycle wheels fall into two general categories: those designed for clincher tires and those designed for tubular (sew-up) tires.
Clincher tires are by far the most widely used. Utility and mountain bicycles usually use clincher tires wider than 5 cm (2 in), sometimes with deep tread. Touring and
hybrid bicycles commonly have clincher tires that are 2.9 to 3.8 cm (1.125 to 1.5 in) wide, and road- and track-racing bicycles usually have clincher tires less than 2.5
cm (1 in) wide. Air pressures for clincher tires range from as low as 35 pounds per square inch (psi) for the fattest mountain-bike tires to more than 150 psi for the
narrowest racing tires. Rims designed to accept clincher tires are usually made of steel, a steel alloy, or aluminum. The rims have a roughly U-shaped cross section with

the two open sides facing out toward the tire. Clincher tires are also U-shaped in cross section, but their two open sides point in toward the hub. When the inner tube is
inflated, the air pressure keeps the tire firmly in place against the rim.
Tubular tires are very narrow (as narrow as 19 mm, or 0.75 in) and highly pressurized (120 to 170 psi) to give racing bicycles the least friction with the ground and the
most nimble handling. In cross section, tubular tires are indeed shaped like a tube, completely enclosing the inner tube. The edges of tubular tires are hand-sewn
together with a special needle and thread; the sewn edges are then glued onto a smooth rim. The rim has no projecting sides to hold the tire in place. The high air
pressure within the tire pushing inward against the rim secures the tire. The rim, which may be made of aluminum alloy, carbon-fiber composite, or even wood, may be
a hollow structure in cross section to maximize strength while minimizing weight.
Specialized wheels without wire spokes have been designed for high-performance racing to minimize the wind resistance and turbulence normally created by spokes
slicing through air at high speed. One design is a monocoque (single-unit) or injection-molded solid structure consisting of three to five thin, flat airfoil blades
(sometimes still called spokes) connecting the rim to the hub. The airfoils actually generate a bit of lift. Another design is a disk wheel, in which the rim is attached to
each side of the hub by a thin plane of fiberglass or stringed Kevlar under tension. Disk wheels are generally used only for the rear wheel, because their unperforated
surface can make the bicycle susceptible to crosswinds. There are many other specialized wheel designs that have been marketed in recent years to reduce weight and
wind resistance.
Mountain-bicycle wheels are usually 65 cm (26 in) in diameter and are clinchers. Road-bicycle wheels, which may be clinchers or tubular, used to be either 70 cm (28 in)
in diameter or the slightly smaller size known as 700 C, which allegedly stands for 700 mm but in reality ranges from 66.6 to 68.6 cm (26.2 to 27.0 in) in diameter.
(The actual sizes of bicycle tires vary and are only partially standardized.) By the late 1980s the 700 C size was featured on most new road bicycles. BMX bicycles
usually have wheels 50 cm (20 in) in diameter, and some folding bicycles have even smaller wheels.

C

Saddle

The bicycle saddle, or seat, is made of leather, vinyl, plastic, or gel-filled material (for extra padding) and is wrapped around a metal frame bolted to the seat post. In
general, a very wide saddle is less desirable than a narrower one, because it is heavier and may interfere with the movement of the thighs while pedaling. The
narrowest saddles are usually preferred by male riders. Some manufacturers have designed saddles to accommodate the wider pelvic structure of female cyclists.
Saddles have also been designed with cutouts in the hard base material and grooves down the center to relieve pressure on pelvic nerves and the pelvic "sit bones." To
fit a cyclist, the height of the saddle can be adjusted by 15 cm (6 in) or more by raising or lowering the seat post in the bicycle frame's seat tube. For further
accommodation of fit, the saddle also may be slid a few centimeters forward or back on two parallel rails welded to its frame. A joint where the seat post bolts onto the
saddle allows the saddle's nose to be slightly tilted up or down.

D

Brakes

Four principal braking systems are used on bicycles: coaster, caliper, disc, and drum brakes.
Coaster brakes, which are mounted inside the hub of the rear wheel, are usually found only on single-speed utility bicycles or on children's bicycles (most children do
not have hands big or strong enough to squeeze brake levers). Coaster brakes are operated by rotating the foot pedals backward half a revolution until they lock; this
expands a mechanism inside the hub that creates friction on an internal brake sleeve.
Caliper brakes are almost universal on multigeared road, BMX, and utility bicycles. They consist of a pair of arms that are pivoted together and fitted with brake pads.
These arms close onto the metal wheel rims in a scissor-like motion. They are controlled by hand levers mounted on the handlebars that connect to the arms by way of
cables. Caliper brakes are available with either side-pull or center-pull cables. Side-pull brakes are frequently used in road racing because their braking force is easily
feathered (adjusted minutely). Center-pull brakes are sometimes found on recreational and light touring bicycles; their braking leverage is greater and they can be
designed for the larger clearances required for wider tires and rims.
Cantilever, cam, and U brakes--always of a center-pull design--are caliper brakes with exceptionally large brake pads and leveraging mechanisms to increase the
amount of braking force delivered. These large, leveraged brakes are found most commonly on mountain, touring, commuter, hybrid, and BMX bicycles, where a
premium is placed on retaining braking ability even when the bicycle is ridden through dirt, water, or mud.
Disc and drum brakes, which operate much like the disc and drum brakes on automobiles, are less common but are sometimes used on tandems, utility bicycles,
mountain bicycles, and recumbents that must carry heavy loads.

E

Handlebars

A rider steers a bicycle primarily by shifting his or her body weight; a rider may also steer the bicycle by pivoting the front wheel with the handlebars. (The handlebars,
although colloquially referred to in the plural, are usually a single piece of tubing.) Handlebars come in various shapes and are most commonly made of light steel or
aluminum alloys. Many racing, recreational, and touring bicycles are equipped with some design of dropped handlebars, which curl down at the ends to allow the rider
several alternate riding positions for aerodynamic streamlining or for the relief of muscle tension. Racing, mountain, and some recreational bicycles may also be
equipped with an aerobar, a curved, V-shaped piece of tubing on which a rider may rest his or her forearms while crouching forward in an aerodynamic position.
Mountain, hybrid, and commuter bicycles are commonly equipped with upright or flat handlebars to allow the rider to sit nearly vertically for visibility and comfort.
Some flat handlebars have adjustable perpendicular ends to give the cyclist greater leverage on climbs. In recumbents, depending on design, the handlebars may be
positioned in front of the cyclist's body or below the cyclist's hips. BMX and freestyle bicycles have high-rise handlebars reminiscent of the old banana-seat bicycles that
were popular with children in the 1960s and 1970s.

F

Pedals

The pedals transfer human muscle power to the drive train of the bicycle. Some pedals, such as the metal rat-trap design used on utility bicycles and old ten-speeds
and the more recent ATB (all-terrain bicycle) or platform design used on some mountain and BMX bicycles, allow the feet to simply rest on them. The pedals convey
motive force only when the feet push down during the front half of each pedal stroke.
Much mechanical advantage is gained, however, if a cyclist's feet are attached to the pedals so that the cyclist can also use muscle power to pull up on the pedals in the
back half of each pedal stroke. Two of the oldest ways of attaching the feet to the pedals (originating in the early 20th century) are toe clips and cleats.
Toe clips are curved, springy cages, commonly made of metal or high-impact plastic, that are bolted to the front of a counterweighted pedal to enclose the toes of the
cyclist's shoes. Using a leather or fabric side strap, the toe clips may be cinched down to grip the shoe. The optimum gripping force holds the foot on the pedal with

minimum play but still allows the cyclist to free the foot as needed when coming to a stop. Toe clips work with virtually any type of ordinary walking shoe, so cyclists can
walk around once they stop riding.
Cleats are permanent attachments that project from the soles of special hard-soled cycling shoes. These attachments lock the feet in place against the pedals. Cleats
enable a cyclist to deliver power to the pedals more efficiently than is possible with toe clips alone, making them popular for racing. However, toe clips without cleats
have long been preferred in touring, commuting, and ordinary recreational cycling because walking in the shoes with the projecting cleats is virtually impossible.
Manufacturers since the 1970s have devoted much attention to developing clipless or uncleated systems. The cyclist must still wear special shoes, but the shoes attach
to devices that replace conventional pedals and toe clips. The cyclist inserts or removes the foot from the attachment by a twisting motion of the ankle. Unlike cleats,
however, the attachment mechanism on the shoe is recessed into the sole instead of projecting from it. Such clipless or uncleated systems yield the efficiency of cleats
without impairing the cyclist's ability to walk, an innovation that has been widely embraced. By the 1990s some manufacturers had developed shoes for clipless pedals
that were nearly indistinguishable in appearance from normal sneakers or loafers. The only disadvantage to the clipless system is that the attachments that replace the
pedals make it difficult or impossible to ride the bicycle while wearing ordinary shoes.

G

Drive Train

To propel most bicycles, the rider straddles the saddle and uses his or her legs and feet to rotate the pedals around the crank axle. The pedals, in turn, are fixed to a
chain ring (sprocket) with teeth that engages the bicycle's continuous chain. The chain then transmits the pedaling action to a cog on the hub of the rear wheel, causing
the rear wheel to rotate and drive the bicycle forward. On most bicycles, cogs are mounted on a freewheel or cassette mechanism that allows the rear wheel to continue
turning even if the rider stops pedaling and coasts.

H

Gears

Single-speed, or fixed-gear, bicycles feature a single chain ring in front that is centered on the pedals and only one cog in the rear, centered on the rear hub. Old threespeed bicycles had one front chain ring and an internal gear mechanism enclosed in a drum inside the rear hub. Bicycles having anywhere from 5 to 27 speeds
dominated the bicycle market in western Europe, the United States, and other developed countries by the late 1990s. These bicycles offer a choice of gear ratios, or
speeds, that result from the interaction of the bicycle chain with one to three front chain rings and a cluster of five to nine cogs of various sizes that are mounted on the
freewheel or cassette mechanism of the rear wheel. The number of speeds a bicycle allows can be calculated by multiplying the number of cogs by the number of chain
rings. A 16-speed bicycle, for example, has eight cogs and two chain rings (known in bicycling parlance as a double crank), and a 27-speed bicycle has nine cogs and
three chain rings (known as a triple crank).
On most multispeed bicycles, gears are changed by means of derailleurs that, when activated by levers mounted on or near the handlebars, mechanically derail the
chain by pushing it toward or away from the bicycle's frame so it moves from one sprocket to another. The rear derailleur moves the chain across the cogs for the finer
differences in gear ratios needed for most shifting. A spring-loaded arm under the cogs takes up or lets out slack in the chain to keep the tension consistent regardless
of the gear ratio chosen. The front derailleur moves the chain across the chain rings to alter the whole range of available shifting (to change, say, from a fast downhill
cruise to a slow uphill climb).
Although the derailleur was invented in 1899, it didn't become popular until roads were paved because of its tendency to be fouled by mud and grit. Even with the tenspeed's rise in popularity in the 1960s, derailleurs were a source of frustration to many novices because their operation required the cyclist to develop some skill in
sensing the friction point at which the gears would change and the point at which the derailleur was securely in gear. Those frustrations were eliminated in the 1980s
with the invention of reliable indexed, or click, shifting, which latches the shift lever with a secure click to let the rider know that a shift from one gear to the next is
complete. Because indexed shifting is faster to use, particularly when downshifting at the base of hills in preparation for a climb, such systems are popular with racing
and touring cyclists as well as with novices.
Some manufacturers have experimented with gears that shift automatically. These products have had some commercial success, particularly on recreational bicycles
used by novice riders.

I

Suspension System

In most bicycles, the only suspension systems for minimizing the impact of uneven roads on the rider and the bicycle is a combination of the air in the inflated tires and
the flexure of the cyclist's knees. Some utility bicycles and older bicycles also have springs under the saddle.
The advent of mountain bicycling (and, to a lesser extent, BMX riding) as a serious sport led to the invention and improvement of hydraulic shock absorbers on the front
fork. These shock absorbers minimize the severe beating on the comparatively delicate threads and bearings in the bicycle's headset during cross-country rock-hopping
and stump-jumping. Suspension mechanisms have also been developed for the rear triangle of these bicycles to provide for increased shock absorption and better
control while riding on rough terrain.

IV

SAFETY EQUIPMENT AND ACCESSORIES

Cycling, like skiing, boating, and other active sports, has its hazards. These hazards gradually became recognized, and as a result safety equipment was developed to
prevent injury. The most common hazards are hitting the head in a fall and not being visible at night to motor vehicles. In addition to accessories for safety, options are
available for extending cycling comfort and versatility.

A

Helmets

The most serious bicycling injuries may be prevented by the use of proper head protection. Most helmets have an interior lining of crushable foam, designed to absorb
the force of an impact, and a thin outer shell of high-impact plastic, usually perforated for ventilation.
Most good bicycle helmets meet impact standards set by the American National Standards Institute (ANSI), the Snell Memorial Foundation, or the Consumer Product
Safety Commission (CPSC). The CPSC standard was mandated by United States law in 1999. By the mid-1990s many states of the United States had passed laws
requiring minors to wear bicycle helmets while cycling.

B

Reflectors and Lights

New bicycles sold in the United States must be equipped with front, side, and rear reflectors, according to CPSC regulations. The front and side reflectors are usually

white, and the rear reflector is red. The front reflector is usually installed near the headset, the rear reflector under the seat or at the end of a rear rack, and the side
reflectors on the spokes of the wheels. Cyclists also often wear reflective clothing.
Lights, powered either by batteries or by generators activated by the rotation of the bicycle wheels, may clip to the handlebars and seatstays. Some cyclists also wear
helmet-mounted headlights and white, amber, or red flashing taillights attached to their bicycles, helmets, backpacks, arms, legs, or belts.

C

Rearview Mirrors

Rearview mirrors may attach to the handlebars, helmet, or cyclist's glasses. They are useful for sighting automobile traffic approaching from behind while allowing the
cyclist to simultaneously keep watch on the road ahead.

D

Padded Shorts and Gloves

Padded shorts and gloves are useful both for comfort and for safety. Cycling shorts often have padding of natural or artificial chamois, a gel insert, or some other
material that cushions the impact of road vibration on a cyclist's pelvic sit bones. Fingerless or full-fingered padded gloves protect a cyclist's hands against potential
nerve damage from road vibration and from injury in the event of a fall.

E

Racks and Panniers

Racks and panniers are useful for carrying things while commuting or touring, such as briefcases, camping equipment, and clothing. Most panniers are designed to clip
onto standard front and rear racks for easy installation and removal. Objects are most commonly strapped onto racks using bungee cords, which are stretchy cords of
differing lengths and widths with a strong hook on each end.

F

Child Seats and Trailers

A child seat bolted to the rear of a bicycle allows a parent to carry a child weighing under 18 kg (40 lb). Trailers towed behind the bicycle can carry one or two children
totaling up to 45 kg (100 lb).

V

HISTORY OF THE MODERN BICYCLE

The bicycle was not invented by any one person. Rather, it is an outgrowth of ideas and inventions dating to the late 18th century. Some people claim the bicycle's
history goes back even further, citing certain drawings by Leonardo da Vinci of a two-wheeled vehicle.

A

Early Attempts

The Comte de Sivrac was seen in Parisian parks in 1791 riding a two-wheeled wooden hobby horse by an unknown maker; it was initially known as a célérifère and later
as a vélocifère. The rider straddled a padded saddle and propelled the vehicle with his feet on the ground, much as a child of today rides a scooter. Karl Friedrich
Christian Ludwig, Baron Drais von Sauerbronn, of Mannheim, Baden (in present-day Germany), added a steerable front wheel in 1817, creating the Draisienne, or
dandy horse, also known as a vélocipède. It was patented in Baden, the United Kingdom, the United States, and France.
In 1839 Kirkpatrick Macmillan, a blacksmith in Courthill, Dumfriesshire, Scotland, attached iron rims to the dandy horse's wooden wheels, added a forked frame, and
installed a pair of treadles in front that transmitted foot power to the rear wheel, creating a machine that could travel up to 23 km/h (14 mph). This combination
produced what is generally considered the first true bicycle, but it was not popular.
In 1861 pedals were added to the front wheel of a vélocipède in the workshop of Pierre Michaux and his son Ernst in Paris, France. This creation, which became
immensely popular, was known by the apt name of boneshaker because of its rough ride. The French regard Pierre Michaux as the father of the bicycle, but his credit
for the invention was contested by Pierre Lallement, one of his employees.
Bicycle design was sidetracked in the 1870s as manufacturers pursued the notion that larger wheels made for faster bicycles, since each rotation of the pedal caused a
larger-diameter wheel to roll farther than it would a smaller-diameter wheel (thus giving rise to the custom, still observed by expert cyclists, of specifying bicycle gears
in gear-inches). In modern terminology, larger wheels produced the equivalent of a higher gear.
This concept led in 1872 to the development of the Ariel highwheeler. Created by James Starley in England, the Arial highwheeler had a huge front wheel. Pedals were
attached to the hubs of this wheel, and a much smaller wheel was located in the rear for stability. Starley's aim was to increase the speed of the vélocipède by giving it
a large front wheel but to reduce the weight by using a small rear wheel and several other innovations, among them making the wheels of iron with wire spokes under
tension. Starley's Ariel highwheelers typically weighed about 23 kg (50 lb), less than half of what some of his competitors' bicycles weighed.
The highwheeler was hard to mount and dismount, however, and it could throw riders from their high perch if the front wheel encountered a stone or pothole, making
"take a header" a household phrase for a crashing head-first. The fastest variety that was still relatively practical and safe had a front wheel about 1.5 m (about 5 ft)
high and a rear wheel at least 41 to 46 cm (16 to 18 in) high. The highwheeler became widely known in England as the penny-farthing, after the large and small coins
in circulation at that time, and in the United States as the ordinary, because it rapidly became the most common bicycle in use there. Colonel Albert A. Pope, the first
major American bicycle manufacturer, first produced a model called the Columbia highwheeler in his Connecticut factory in 1876.

B

The Safety Bicycle

A crucial design advance was the invention of the safety bicycle. Although its equal-sized wheels made it easier to mount and distinctly safer to ride than the
highwheeler, it did not become truly popular until the 1890s. In the 1870s, H. Bates of Croyden, England, built a bicycle, named the Flying Dutchman, that used a drive
connected to the rear wheel. This drive, which consisted of pulleys and a cord, was improved by the safety Bicyclette of Henry J. Lawson, which featured a chain and
sprocket drive connected to the rear wheel.
Around 1885 John Kemp Starley (a nephew of James Starley) and William Sutton introduced the Rover safety bicycle, a machine that featured two equal-sized wheels
76 cm (30 in) in diameter and a chain-driven rear wheel. Around the same time, C. A. Linley and J. Biggs introduced the Whippet spring-frame safety bicycle, which
featured a triangular frame that hinted at the diamond shape that is now standard, with set positions for the saddle, pedals, and handlebars. The frame also had two
springs that were intended to absorb road shock; this feature made the Whippet very popular until John B. Dunlop's newly developed pneumatic (air-filled) tires were
added in 1889. Further innovations over the next decade included the use of ball bearings to reduce friction on moving parts, assembly-line production methods, steel

tubing, two- and three-speed hub gears, a coaster brake, and derailleur gears.
The development of the safety bicycle and its tremendous popularity in the 1890s also ushered in many social changes, among them changes in women's fashions.
Bloomers, for example, were named for Amelia Bloomer, who strongly advocated them for riding a bicycle.

C

The Decline of Cycling

Many of the innovations made by early bicycle designers contributed to the development of the automobile industry. In fact, many of the early automobile and
motorcycle designers started out as bicycle designers, among them Gottlieb Daimler of Germany and Bill Harley and Arthur Davidson of Milwaukee, Wisconsin. Cycling
enthusiasts also clamored for better roads, led by the League of American Wheelmen, which was by 1890 the world's largest athletic association. The increasing
popularity of motorized vehicles ultimately led to a decline in the popularity of adult cycling between 1900 and 1920, particularly in the United States. The average
annual bicycle production in the United States fell from 1 million units during the 1890s to 335,000 units during the 1920s. Prices declined 70 to 80 percent during the
same period.
Bicycle sales rebounded somewhat in the United States between 1924 and 1941, led by Arnold, Schwinn & Co., which eventually captured nearly 20 percent of the
market. Two keys to this resurgence were the repositioning of the bicycle in the market, primarily for children and young teens, and the addition to it of the most flashy
accessories of the automobiles and motorcycles of the time. Such appealing nonessential features included whitewalled balloon tires, front fender ornaments, dual
headlights, illuminated speedometers, spring fork shock absorbers, and even a hollow "gas tank" under the top tube containing a battery-operated noisemaker that
sounded like a motor. In addition, the models were given names such as Autocycle, Motorcycle, and Streamlined Cycleplane. Perhaps most famous was Schwinn's
elegant Black Phantom.
Cycling remained popular in Europe, in part because the population there did not embrace the automobile as wholeheartedly as Americans did and did not have the
same need to cover great distances over vast open spaces. As a result, European manufacturers made steady progress in improving the technology for serious cycling,
developing gearshifting mechanisms, lighter-weight tubing, wheels, tires, and other components.

D

The Bicycle Boom

In the United States, where bicycle design essentially stagnated for the first half of the 20th century, the popularity of adult bicycling began a resurgence with the
publicity surrounding President Dwight D. Eisenhower's first heart attack in 1955. Paul Dudley White, a Boston heart specialist called as a consultant, recommended
bicycling as a therapeutic activity for coronary patients and those at high risk of coronary disease.
The Kennedy administration's emphasis on nationwide programs to promote physical fitness also encouraged bicycling. Between 1960 and 1966 annual bicycle sales in
the United States increased from 3.8 million to 6 million. American buyers now turned in large numbers to the sophisticated offerings of European developers (and later,
Japanese manufacturers), who had made bicycles more attractive and easier to ride by radically reducing their weight and adding gears to help with climbing hills.
Compared to the 23 to 27 kg (50 to 60 lb) typical for the one-speed balloon-tire bicycle of the 1930s and 1940s, the three-speed English racer averaged only 20 kg (45
lb), and the derailleur ten-speed weighed under 16 kg (35 lb).
As a result of the energy crisis of the 1970s, when the Organization of Petroleum Exporting Countries (OPEC) raised the price of petroleum sharply, and in part because
of a heightened environmental awareness, alternatives to costly automobile transportation were once again popular. Using a bicycle for errands and commuting as well
as for recreation boosted interest in cycling in the United States. Interest in bicycle commuting waned in the early 1980s, however, after OPEC fell into disarray, oil
prices declined, and fuel-efficient automobiles came onto the market.
Meanwhile, in the late 1970s in Marin County, California, several bicycle designers (including Gary Fisher and Otis Guy) were experimenting with adding triple cranks,
26-inch wheels, and wide, low-pressure tires to touring frames to create the all-terrain bicycle (ATB), or mountain bicycle. This vehicle could plow through mud and
sand, climb rocky tracks, and jump tree stumps; it enabled cyclists to explore backwoods trails hitherto accessible only to hikers or horseback riders.
In the early and mid-1980s the mountain bike single-handedly gave the U.S. bicycle industry a boost, as it was also popular in urban areas as a city bike or commuter
bike for riding over city streets with their potholes and sewer grates. The combination of low gears, wide tires, and a short-wheelbase racing frame also made the
mountain bike lively and nimble, giving rise to the sport of mountain-bike racing at so-called fat-tire festivals.
In the late 1980s and early 1990s a combination of the mountain bike and the touring bike resulted in the hybrid bike, popular among experienced commuting and
touring cyclists as well as with novice riders.
The increasing popularity of bicycles during the 1980s and 1990s led to the introduction of organized tours. Many of these tours cover large distances within and across
states, run from three to eight days in length, and have hundreds and even thousands of riders who participate. RAGBRAI (Register Annual Great Bicycle Ride Across
Iowa), for example, has attracted as many as 23,000 people. Touring companies that offer recreational and vacation bicycle tours in many areas of the country have
multiplied as well.
Bicycle fundraising events have also become popular and have attracted thousands of people across the country during the past few decades. Many nonprofit
organizations use them to raise funds, educate the public, and increase awareness of their efforts.
The success of American cyclists in international competitions, particularly the Tour de France, has also fostered the resurgence of bicycling in the United States. The
Tour de France is considered the premier stage race in cycling, and Greg LeMond became the first American to win that race in 1986. He won again in 1989 after
overcoming a near fatal hunting accident, and then again in 1990. Lance Armstrong became the second American to win the Tour de France, in 1999, after overcoming
cancer; he repeated as champion in 2000, 2001, 2002, 2003, and 2004 to set the record for most wins with six. Armstrong won again in 2005 for his seventh
consecutive Tour de France victory and then retired from racing. Through their victories, LeMond, Armstrong, and other American cycling champions contributed greatly
to an increase in the popularity of bicycles in the United States. See also Cycling.

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