History

Main article: History of the bicycle
Drais' 1817 design made to measure

Several innovators contributed to the history of the bicycle by developing predecessor human-powered vehicles, including the velocipede. The documented ancestors of today's modern bicycle were known as pushbikes, Draisines or hobby horses. To use the Draisine, first introduced to the public in Paris by the German Baron Karl von Drais in 1818[3], the operator sat astride a wooden frame supported by two in-line wheels and pushed the vehicle along with their feet while steering the front wheel.
A penny-farthing or ordinary bicycle photographed in the Škoda museum in the Czech Republic

Scottish blacksmith Kirkpatrick MacMillan refined this in 1839 by adding a mechanical crank drive to the rear wheel, thus creating the first true "bicycle" in the modern sense. In the 1850s and 1860s, Frenchmen Ernest Michaux and Pierre Lallement took bicycle design in a different direction, placing the pedals on an enlarged front wheel. Their creation, which came to be called the "Boneshaker" or "penny-farthing" (more formally an ordinary bicycle), featured a heavy steel frame on which they mounted wooden wheels with iron tires. The primitive bicycles of this generation were difficult to ride, and the high seat and poor weight distribution made for dangerous falls.

The subsequent dwarf ordinary addressed some of these faults by adding gearing, reducing the front wheel diameter, and setting the seat further back, with no loss of speed. Having to both pedal and steer via the front wheel remained a problem. Starley's nephew, J. K. Starley, J. H. Lawson, and Shergold solved this problem by introducing the chain drive. These models were known as dwarf safeties, or safety bicycles, for their lower seat height and better weight distribution. Starley's 1885 Rover is usually described as the first recognizably modern bicycle. Soon, the seat tube was added, creating the double-triangle, diamond frame of the modern bike.
Bicycle in Plymouth at the start of the 20th century

New innovations increased comfort, and ushered in the 1890s Golden Age of Bicycles. In 1888, Scotsman John Boyd Dunlop introduced the pneumatic tire, which soon became universal. Soon after, the rear freewheel was developed, enabling the rider to coast without the pedals spinning out of control. This refinement led to the 1898 invention of coaster brakes. Derailleur gears and hand-operated, cable-pull brakes were also developed during these years, but were only slowly adopted by casual riders. By the turn of the century, bicycling clubs flourished on both sides of the Atlantic, and touring and racing were soon extremely popular.

Bicycles and horse buggies were the two mainstays of private transportation just prior to the automobile, and the grading of smooth roads in the late 19th century was stimulated by the wide use of these devices.

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Technical aspects
Reflectors for night riding are one of many available safety accessories

Drivetrain

For more details on this topic, see bicycle gearing.
Shimano XT rear derailleur on a mountain bike

The drivetrain begins with pedals which rotate the crank arms, which are held in axis by the bottom bracket. Attached to one crank arm may be one or more chainrings or sprockets which drive the chain, which in turn rotates the rear wheel via the rear sprockets (cassette or freewheel). A gearing systems is used to vary the number of rear wheel revolutions produced by each turn of the pedals.

Since cyclists' legs are most efficient over a narrow range of cadences, a variable gear ratio is helpful to maintain an optimum pedalling speed while covering varied terrain.

When the bicycle chain shifts to a larger rear sprocket, or to a smaller front sprocket (a lower gear) every cycle on the pedal leads to fewer rotations in the freewheel (and hence the rear wheel). This allows the force required to move same distance to be distributed over more pedal cycles, reducing fatigue when riding uphill, with a heavy load, or against strong winds. The reverse process allows the cyclist to spend fewer pedal cycles to maintain a higher speed, but with more effort per cycle.

Road bicycles have close set multi-step gearing, which allows very fine control of cadence, while utility bicycles offer fewer, more widely spaced speeds. Mountain bikes and many entry-level racing bicycles offer an extremely low gear to facilitate climbing slowly on steep hills. Fixed-gear bicycles have only one gear combination.

Steering and seating

The handlebars turn the fork and the front wheel via the stem, which rotates within the headset. Three styles of handlebar are common. Upright handlebars, the norm in Europe and elsewhere until the 1970s, curve gently back toward the rider, offering a natural grip and comfortable upright position. Drop handlebars are "dropped", offering the cyclist either an aerodynamic "crouched" position or a more upright posture in which the hands grip the brake lever mounts. Mountain bikes feature a straight handlebar which can provide better low-speed handling due to the wider nature of the bars.

Saddles also vary with rider preference, from the cushioned ones favoured by short-distance riders to narrower saddles which allow more room for leg swings. Comfort depends on riding position. With comfort bikes and hybrids the cyclist sits high over the seat, their weight directed down onto the saddle, such that a wider and more cushioned saddle is preferable. For racing bikes where the rider is bent over, weight is more evenly distributed between the handlebars and saddle, and the hips are flexed, and a narrower and harder saddle is more efficient. Differing saddle designs exist for male and female cyclists, accommodating the genders' differing anatomy, although bikes typically are sold with saddles most appropriate for males.

A recumbent bicycle has a reclined chair-like seat that some riders find more comfortable than a saddle, especially riders who suffer from certain types of seat, back, neck, shoulder, or wrist pain. Recumbent bicycles may have either under-seat or over-seat steering.

Brakes

Main article: Bicycle brake systems
Semi low-profile cantilever brake

Modern bicycle brakes are either rim brakes, in which friction pads are compressed against the wheel rims, internal hub brakes, in which the friction pads are contained within the wheel hubs, or disc brakes. Disc brakes are common on off-road bicycles, tandems and recumbent bicycles, but are considered impractical on road bicycles, which rarely encounter conditions where the advantages of discs are significant. Hub drum brakes do not cope well with extended braking, so rim or disc brakes are favoured in hilly terrain.

With hand-operated brakes, force is applied to brake levers mounted on the handlebars and transmitted via Bowden cables or hydraulic lines to the friction pads. A rear hub brake may be either hand-operated or pedal-actuated, as in the back pedal coaster brakes which were popular in North America until the 1960s, and are still common in children's bicycles.

Track bicycles do not have brakes. Brakes are not required for riding on a track because all riders ride in the same direction around a track which does not necessitate sharp deceleration. Track riders are still able to slow down because all track bicycles are fixed-gear, meaning that there is no freewheel. Without a freewheel, coasting is impossible, so when the rear wheel is moving, the crank is moving. To slow down one may apply resistance to the pedals. While it is illegal in most jurisdictions to cycle on roads without brakes, a fixed-gear bike without brakes can be slowed by skidding the rear wheel. This involves unweighting the rear wheel and applying a backwards force to the pedals, causing the rear wheel to lock up and slide along the road. Most track bike frames and forks do not have holes for mounting brakes, although with their increasing popularity among some road cyclists, some manufacturers have designed their track frames to enable the fitting of brakes.



Suspension

Suspension

Main article: Bicycle suspension

Bicycle suspension refers to the system or systems used to suspend the rider and all or part of the bicycle in order to protect them from the roughness of the terrain over which they travel. Bicycle suspension are used primarily on mountain bicycles, but are also common on hybrid bicycles, and can even be found on some road bicycles as they can help deal with problematic vibration.

Accessories and repairs

optional accessories on sports bicycles, are standard features on utility bicycles to enhance their usefulness and comfort. Mudguards (or fenders) protect the cyclist and moving parts from spray when riding through wet areas and chainguards protect clothes from oil on the chain. Kick stands keep a bicycle upright when parked. Front-mounted baskets for carrying goods are often used. Rear racks and panniers or other carriers can be used to carry equipment or cargo. Parents sometimes add rear-mounted child seats and/or an auxiliary saddle fitted to the crossbar to transport children.
Touring bicycle equipped with head lamp, pump, rear rack, fenders/mud-guards, and numerous saddle-bags.

Toe-clips and toestraps and clipless pedals help to keep the foot planted firmly in the proper position on the pedals, and enable the cyclist to pull as well as push the pedals. Technical accessories include cyclocomputers for measuring speed and distance. Other accessories include lights, reflectors, tire pump, security lock, mirror, and bell.[4]

A bicycle helmet reduces injury in the event of a collision, and a certified helmet is legally required for some riders in some jurisdictions. Helmets are classified as an accessory[4] or an item of clothing by others.[5]


Many cyclists carry tool kits, containing at least a tire patch kit (and/or a spare tube), tire levers, and hex wrenches. More specialised parts now require more complex tools, including proprietary tools specific for a given manufacturer. Some bicycle parts, particularly hub-based gearing systems, are complex, and many prefer to leave maintenance and repairs to professional bicycle mechanics. Others maintain their own bicycles, enhancing their enjoyment of the hobby of cycling.

In some areas it is possible to purchase road-side assistance from companies such as the Better World Club.