Downhill biking (DH) is a gravity-assisted time trial mountain biking event. Riders race against the clock, usually starting at intervals of 30 seconds (seeded from slowest to fastest), on courses which typically take two to five minutes to complete. Riders come from all around the world. Riders are timed with equipment similar to that used in Downhill skiing. The placing is determined by the fastest times to complete the course; races are often won by margins of under a second. As the name of this discipline implies, downhill races are held on steep, downhill terrain, resulting in high speed descents, and with extended air time off jumps and other obstacles. The 2010 Downhill World Champion is Sam Hill from Australia.
Modern race downhill bikes weigh between 14 to 19 kg (30 to 42 pounds), and usually feature full-suspension and frame geometries that lean back farther (slacker geometry) than other mountain bikes. As of 2006, 203 mm (8-inch) is the 'norm' for suspension travel however some commercially available big mountain freeride bikes can have over 300 mm (12-inch). Large-diameter 203–5 mm (8-inch) hydraulic disc brakesmoderate speed. Downhill bikes and freeride bikes are similar but there are some slight differences.Wikipedia
