Bicycles can be categorized in different ways: such as by function, by number of riders, by general

Bicycles have been and are employed for many uses:
Utility: transportation, bicycle commuting, and utility cycling
Work: mail delivery, paramedics, police, couriering, and general delivery.
Recreation: bicycle touring, mountain biking, BMX, physical fitness, and play.
Racing: track racing, criterium, roller racing and time trial to multi-stage events like the Tour of California, Giro d'Italia, the Tour de France, the Vuelta a España, the Volta a Portugal, among others.
Military: scouting, troop movement, supply of provisions, and patrol. See bicycle infantry.
Entertainment and performance: Artistic cycling, Freestyle BMX.

Transporting milk churns in Kolkata, India



A cargo bicycle in Amsterdam, Netherlands



A toy, Abbottabad, KPK, Pakistan.

Technical aspects[edit source | editbeta]



A trailer bike in New York City
The bicycle has undergone continual adaptation and improvement since its inception. These innovations have continued with the advent of modern materials and computer-aided design, allowing for a proliferation of specialized bicycle types.
Types[edit source | editbeta]
Main article: List of bicycle types


Firefighter bicycle


A freestyle BMX bike, an example of a bicycle designed for sport
Bicycles can be categorized in different ways: such as by function, by number of riders, by general construction, by gearing or by means of propulsion. The more common types include utility bicycles, mountain bicycles, racing bicycles, touring bicycles, hybrid bicycles, cruiser bicycles, and BMX Bikes. Less common are tandems, lowriders, tall bikes, fixed gear, folding models, amphibious bicycles and recumbents.
Unicycles, tricycles and quadracycles are not strictly bicycles, as they have respectively one, three and four wheels, but are often referred to informally as "bikes".


Bicycles leaning in a turn
Dynamics[edit source | editbeta]
Main article: Bicycle and motorcycle dynamics
A bicycle stays upright while moving forward by being steered so as to keep its center of mass over the wheels.[21] This steering is usually provided by the rider, but under certain conditions may be provided by the bicycle itself.[22]
The combined center of mass of a bicycle and its rider must lean into a turn to successfully navigate it. This lean is induced by a method known as countersteering, which can be performed by the rider turning the handlebars directly with the hands[23] or indirectly by leaning the bicycle.[24]
Short-wheelbase or tall bicycles, when braking, can generate enough stopping force at the front wheel to flip longitudinally.[25] The act of purposefully using this force to lift the rear wheel and balance on the front without tipping over is a trick known as a stoppie, endo, or front wheelie.
Performance[edit source | editbeta]
Main article: Bicycle performance
The bicycle is extraordinarily efficient in both biological and mechanical terms. The bicycle is the most efficient human-powered means of transportation in terms of energy a person must expend to travel a given distance.[26] From a mechanical viewpoint, up to 99% of the energy delivered by the rider into the pedals is transmitted to the wheels, although the use of gearing mechanisms may reduce this by 10–15%.[27][28] In terms of the ratio of cargo weight a bicycle can carry to total weight, it is also an efficient means of cargo transportation.


A recumbent bicycle
A human traveling on a bicycle at low to medium speeds of around 10–15 mph (16–24 km/h) uses only the energy required to walk. Air drag, which is proportional to the square of speed, requires dramatically higher power outputs as speeds increase. If the rider is sitting upright, the rider's body creates about 75% of the total drag of the bicycle/rider combination. Drag can be reduced by seating the rider in a more aerodynamically streamlined position. Drag can also be reduced by covering the bicycle with an aerodynamic fairing. The fastest unpaced speed on a flat surface is 82.819 mph (133.284 km/h)[29]
In addition, the carbon dioxide generated in the production and transportation of the food required by the bicyclist, per mile traveled, is less than 1/10 that generated by energy efficient cars