A bicycle (also known as a pedal cycle, bike, push-bike or cycle) is a human-powered, two-wheeled machine for locomotion. It consists of a frame, two wheels, a seat and handlebars for steering, and a chain or cranks to transmit power from the rider’s legs to the wheel through a pedal-crank system. Bicycle riders are called cyclists or cyclists.
The bicycle has a wide range of uses, from transportation to recreation. It is relatively simple to construct and maintain, and provides a means of transport that is environmentally friendly, inexpensive, and convenient for many people. It is also a popular sport and a form of exercise, with competitive cycling events such as the Tour de France.
Historians do not know who invented the bicycle, but Italian artist Leonardo da Vinci is credited with drawing a contraption that looked like a bicycle in 1492. In the early 19th century, Baron Karl von Drais de Sauerbrun patented a device similar to the modern bicycle. His invention, which was referred to as the draisienne, enabled a person to sit on the machine and move it by pushing with his feet.
In the 1860s, inventors began to make larger front wheels to enable higher speeds. They also added pedals to make it easier to propel the bicycle. This device became known as the penny-farthing bicycle. In 1890, John Kemp Starley’s improved design, known as the safety bicycle, made it possible for almost anyone to enjoy riding a bike.
Bicycles have either coaster or hand brakes. With coaster brakes, a rider stops by putting pressure on the back wheel. Hand brakes work by using levers on the handles to apply pressure against pads that squeeze against the rim of the wheel. Bicycles also can be equipped with gears to allow the rider to change the amount of resistance they must apply to the pedals in order to travel at varying speeds.
A very small number of bicycles use hydraulic systems to transfer power to the rear wheel, and some have multiple-speed transmissions. Many different designs are available, and some can be modified for specific purposes such as racing or touring. The International Organization for Standardization has a special committee on cycles, TC149, which develops standards for bicycles and their components and accessories.
Most bicycles can be customized with a variety of attachments and parts, such as racks to carry equipment or luggage. Parents may add a child’s seat or a hitch to tow a trailer for carrying cargo or children. Most bikes require regular maintenance to keep them in good working condition. Bicycles are relatively simple compared with automobiles, and many cyclists learn to do routine maintenance themselves. Some of the more complex adjustments and replacements can be performed only by a professional bicycle mechanic. It is important to know how to maintain a bicycle in order to avoid accidents. It is also important to learn to ride safely on the road, as laws and common sense require that bicycles obey the rules of the road.