A bicycle is a vehicle consisting of two wheels attached to a frame and steered by a fix tandem, and propelled by the share force of the user who put pressure on pedals that make the wheel spin. The invention of the bicycle date far back to the 17 th century, and since then has been constantly modified during the past decades to reach the bicycle who know today. The first bicycle, a wooden scooter-like vehicle, named a "," was invented by Comte Mede de Siv rac of France. It consisted of two big wheels connected to a wooden beam. At that time, there were no handlebar, no pedals, instead the rider sat on a cushion and pushed his feet against the ground. In 1817, Baron Karl von Dra is of Germany invented a improved model called a ", which added a steering bar connected to the front wheel.

Twenty years later, a Scottish blacksmith, Kirkpatrick Macmillan, added foot pedals to the Draisienne. In the 1870's came a bike called a penny- Farthing. It consisted of a huge front wheel, 1. 5 meters tall, and a very small back wheel. The advantage of this model was that it could travel a greater distance with single turn of the pedals. But because it the wheels were so tall, the bicycle was unstable and many people wouldn't try it.

In 1885, J. K. Stanley, an English bicycle manufacturer, produced the first commercially successful bicycle. It was much lower than the penny-Farthing with two wheels of the equal size, making the bicycle much more stable. It was the first bicycle that incorporated the design and parts of today's bike. Later, the iron tires were replaced with solid rubber tires and patented name "bicycle" was given to it.

Years later, with the coming of the industrial revolution, the bicycle industry lost ground and almost disappeared. The 1900's brought the invention of cars, and the bike sales dropped dramatically. But since the 1960 and 1970's, air pollution, and the need for physical fitness has prompted many people to choose bike riding as a form of exercise and transportation, and the biking industry exploded. The advantages of bikes are far greater than any other types of transportation: there cheap, there fast, there don't pollute the planet and they " re enjoying to ride and provide greater physical activity that leads to a better health.

Today, there are many types of bikes, each adapted for the terrain and the activity. The Mountain bike This type of bike was greater over twenty-five years ago and his has become one of the most popular type. Mountain bikes have sturdy frames, flat handlebars, and wide knobby tires, suiting them to ride over rough terrain, by increasing traction with the ground. Most recent mountain bikes have front and rear suspensions to cushion against road shock. In this category, the suspension have become on the most key asset and many varieties can be found. Some varieties of suspension include "elastomer forks", which are bouncy ball material that are great at absorbing shocks; "Linkage forks", which is made of rigid forks with a hanged parallelogram where they meet, absorbing shocks; and finally there are "air springs", which use cartridge sprung where air flows and is compressed to provide a smooth riding.

Road bikes Road bikes are designed for riding on paved roads. They have thin tires mounted on 650- 700 mm wheels. In this category there are two types of road bikes. The first one is Road racers. Racing bikes weigh between 8 and 11 kilograms and there small resistance to air, enable the cyclist to achieve maximum speed. Road racing is the oldest type of bicycle competition.

The first race was held in France in 1869. Today there are several format of bicycle racing: There is stage racing, such as the Tour-de-France, with may last many weeks; one-day events, such as the world championship road race and the Olympic road race, only last a day; and time trials, road racing that are timed by clock. The second type is more of a recreation bike, a touring bike. They weight between 9 and 14 kilograms and have attachments for extra-racks and water bottles. These bikes are more stable because they have longer wheel base and could support a heavier load.

Hybrids Hybrids are a cross between a mountain bike and a road bike. The are made for road and off road biking, but have few limitation in both cases. Their tires are wider than road bikes but thinner than mountain bikes tires. Speciality bicycles These types of bike have special features. The tandem carries two riders, on in front of the other.

Each rider uses a separate set of pedals, but there is only one chain between them. Such bikes are existed for quite a while and are still popular in some places such as China.