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Motocross is a form of off-road motorcycle racing held on enclosed off-road circuits. The sport evolved from motorcycle trials competitions held in the United Kingdom.〔(【引用サイトリンク】title=History of Individual supercross World Championships )〕 ==History== Motocross was first evolved in the U.K. from motorcycle trials competitions, such as the Auto-Cycle Clubs's first quarterly trial in 1906 and the Scottish Six Days Trial that began in 1909.〔〔 When delicate balancing and strict scoring of trials were dispensed with in favour of a race to be the fastest rider to the finish, it was called scrambles, said to have originated in the phrase, "a rare old scramble" describing one such early race.〔 Originally known as scrambles racing in the United Kingdom, as the sport grew in popularity, the competitions became known internationally as motocross racing, by combining the French word for motorcycle, ''motocyclette'', or ''moto'' for short, into a portmanteau with "cross country".〔 The first known scramble race took place at Camberley, Surrey in 1924.〔(【引用サイトリンク】title=The birth of motocross: 1924 through 1939 )〕 During the 1930s, the sport grew in popularity, especially in Britain where teams from the Birmingham Small Arms Company (BSA), Norton, Matchless, Rudge, and AJS competed in the events. Off-road bikes from that era differed little from those used on the street. The intense competition over rugged terrain led to technical improvements in motorcycles. Rigid frames gave way to suspensions by the early 1930s, and swinging fork rear suspension appeared by the early 1950s, several years before it was incorporated on the majority of production street bikes.〔(【引用サイトリンク】title=Motocross goes International 1947 through 1965 )〕 The period after World War II was dominated by BSA which had become the largest motorcycle company in the world.〔 BSA riders dominated international competitions throughout the 1940s.〔 In 1952, the FIM, motorcycling's international governing body, created an individual European Championship using a 500 cc engine displacement formula.〔 In 1957 it was upgraded it to World Championship status.〔 In 1962, a 250 cc world championship was created.〔 It was in the smaller 250 cc category that companies with two-stroke motorcycles came into their own. Companies such as Husqvarna from Sweden, CZ from the former Czechoslovakia and Greeves from England, became popular due to their lightness and agility.〔 Stars of the day included BSA works riders Jeff Smith and Arthur Lampkin, with Dave Bickers, Joe Johnson and Norman Brown on Greeves. By the 1960s, advancements in two-stroke engine technology meant that the heavier, four-stroke machines were relegated to niche competitions.〔 Riders from Belgium and Sweden began to dominate the sport during this period.〔 Motocross was introduced to the United States in 1966 when Swedish champion, Torsten Hallman rode an exhibition event against the top American TT riders at the Corriganville Movie Ranch also known as Hopetown in Simi Valley, California. The following year Hallman was joined by other motocross stars including Roger DeCoster, Joël Robert, and Dave Bickers. They dominated the event placing their lightweight two-strokes into the top six finishing positions.〔(【引用サイトリンク】title=Edison Dye and his Flying Circus )〕〔(【引用サイトリンク】title=Corriganville/Hopetown Motorcycle Races )〕 Motocross began to grow in popularity in the United States during this period, which fueled an explosive growth in the sport.〔(【引用サイトリンク】title=Boom Time: American Motocross in the 1970s )〕 By the late 1960s, Japanese motorcycle companies began challenging the European factories for supremacy in the motocross world. Suzuki claimed the first world championship for a Japanese factory when Joël Robert won the 1970 250 cc crown.〔(【引用サイトリンク】title=Joël Robert at the Motorcycle Hall of Fame )〕 The first stadium motocross event was held in 1972 at the Los Angeles Coliseum.〔(【引用サイトリンク】title=The First Supercross )〕 In 1975, a 125 cc world championship was introduced.〔 European riders continued to dominate motocross throughout the 1970s but, by the 1980s, American riders had caught up and began winning international competitions.〔(【引用サイトリンク】title=The young Americans )〕 During the late 1970s and early 1980s, Japanese motorcycle manufacturers presided over a boom period in motocross technology. The typical two-stroke air-cooled, twin-shock rear suspension machines gave way to machines that were water-cooled and fitted with single-shock absorber rear suspension. By 2003, increasingly stringent environmental laws in California forced some manufacturers to develop environmentally friendly four-stroke technology. By 2004, all the major manufacturers have begun competing with four-stroke machines. European firms also experienced a resurgence with Husqvarna, Husaberg, and KTM winning world championships with four-stroke machinery. The sport evolved with sub-disciplines such as stadium events known as supercross and arenacross held in indoor arenas. Classes were also created for all-terrain vehicles. Freestyle motocross (FMX) events where riders are judged on their jumping and aerial acrobatic skills have gained popularity, as well as supermoto, where motocross machines race on both tarmac and off road. Vintage motocross (VMX) events are held for motorcycles usually predating the 1975 model year.〔(【引用サイトリンク】url=http://dev.ahrma.org/?page_id=45 )〕 Many VMX races also include a "Post Vintage" portion, which usually includes bikes dating until 1983. == Major competitions == 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「motocross」の詳細全文を読む スポンサード リンク
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