Gearing Up for Better Bikes
The different gears on a bike allow you to change the distance the bike moves for each turn of the pedals. Cyclists use a low gear to climb hills and to accelerate. In a low gear, the chain connects a small front gear to a large back gear. A high gear is used for speed on level roads or for going downhill. In a high gear, the chain connects a large front gear to a small back gear.
Derailleur Gears
The chain connecting the front chainwheel to the rear wheel sprocket serves as a belt to make the wheel turn faster than your feet. Wheel sprockets of various sizes are used to obtain different speeds. Derailleurs are used to move the chain from one sprocket to another.