A bicycle tire is a tire that fits on the wheel of a bicycle, unicycle, tricycle, quadracycle, bicycle trailer, or trailer bike. They may also be used on wheelchairs and handcycles, especially for racing. Bicycle tires provide an important source of suspension, generate the lateral forces necessary for balancing and turning, and generate the longitudinal forces necessary for propulsion and braking. They are the second largest source, after air drag, of power consumption on a level road. The modern detachable pneumatic bicycle tire contributed to the popularity and eventual dominance of the safety bicycle.