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| section2 = | section3 = | website = }} The MotoGP World Championship is the premier class of motorcycle road racing. It is currently divided into three classes: MotoGP, Moto2 and Moto3. All three classes use four-stroke engines. In 2010, 250 cc two-strokes were replaced by the new Moto2 600 cc four-stroke class. In 2012, 125 cc two-strokes were replaced by the Moto3 250 cc four-stroke class with a weight limit of 65 kg with fuel, and the engine capacity for MotoGP increased from 800 cc to 1,000 cc. Grand Prix motorcycles are purpose-built racing machines that are neither available for purchase by the general public nor able to be ridden legally on public roads. This contrasts with the various production-based categories of racing, such as the Superbike World Championship and the Isle of Man TT Races that feature modified versions of road-going motorcycles available to the public. ==Overview== A Road Racing World Championship Grand Prix was first organized by the Fédération Internationale de Motocyclisme (FIM) in 1949. The commercial rights are now owned by Dorna Sports, with the FIM remaining as the sport sanctioning body. Teams are represented by the International Road Racing Teams Association (IRTA) and manufacturers by the Motorcycle Sport Manufacturers Association (MSMA). Rules and changes to regulations are decided between the four entities, with Dorna casting a tie-breaking vote. In cases of technical modifications, the MSMA can unilaterally enact or veto changes by unanimous vote among its members. These four entities compose the Grand Prix Commission. There have traditionally been several races at each event for various classes of motorcycles, based on engine size, and one class for sidecars. Classes for 50 cc, 80 cc, 125 cc, 250 cc, 350 cc, and 500 cc solo machines have existed at some time, and 350 cc and 500 cc sidecars. Up through the 1950s and most of the 1960s, four-stroke engines dominated all classes. In part this was due to rules, which allowed a multiplicity of cylinders (meaning smaller pistons, producing higher revs) and a multiplicity of gears (giving narrower power bands, affording higher states of tune). In the 1960s, two-stroke engines began to take root in the smaller classes. In 1969, the FIM — citing high development costs for non-works teams — brought in new rules restricting all classes to six gears and most to two cylinders (four cylinders in the case of the 350 cc and 500 cc classes). This led to a mass walk-out of the sport by the previously highly successful Honda, Suzuki and Yamaha manufacturer teams, skewing the results tables for the next several years, with MV Agusta effectively the only works team left in the sport until Yamaha (1973) and Suzuki (1974) returned with new two-stroke designs. By this time, two-strokes completely eclipsed the four-strokes in all classes. In 1979, Honda, on its return to GP racing, made an attempt to return the four-stroke to the top class with the NR500, but this project failed, and, in 1983, even Honda was winning with a two-stroke 500. The 50 cc class was replaced by an 80 cc class, then the class was dropped entirely in the 1990s, after being dominated primarily by Spanish and Italian makes. The 350 cc class vanished in the 1980s. Sidecars were dropped from world championship events in the 1990s (see Superside), reducing the field to 125s, 250s, and 500s. MotoGP, the premier class of GP motorcycle racing, has changed dramatically in recent years. From the mid-1970s through to 2001, the top class of GP racing allowed 500 cc displacement with a maximum of four cylinders, regardless of whether the engine was a two-stroke or four-stroke. Consequently, all machines were two-strokes, due to the greater power output for a given engine capacity. Some two- and three-cylinder two-stroke 500s were seen, but though they had a minimum-weight advantage under the rules, typically attained higher corner speed and could qualify well, they lacked the power of the four-cylinder machines. In 2002, rule changes were introduced to facilitate the phasing out of the two-strokes. The rules permitted manufacturers to choose between running two-stroke engines of 500 cc or less or four-strokes of 990 cc or less. Manufacturers were also permitted to employ their choice of engine configuration. Despite the significantly increased costs involved in running the new four-stroke machinery, given their extra 490cc capacity advantage, the four-strokes were soon able to dominate their two-stroke rivals. As a result, by 2003 no two-stroke machines remained in the MotoGP field. The 125 cc and 250 cc classes still consisted exclusively of two-stroke machines. In 2007, the MotoGP class had its maximum engine displacement capacity reduced to 800 cc for a minimum of five years. For the 2012 season the capacity has increased again to 1,000 cc. The 2008 racing calendar consisted of 18 rounds in 15 different countries (Qatar, Spain which hosted three rounds, Portugal, China, France, Italy, Great Britain, the Netherlands, Germany, the US which hosted two rounds, Czech Republic, San Marino, Japan, Australia and Malaysia). Exclusive to the MotoGP class, there was also a US round at Mazda Raceway Laguna Seca in Monterey, California, for the 800 cc class only; this was because the paddock was not large enough to also include the other two classes. In 2008, a MotoGP event was held at the Indianapolis Motor Speedway for the first time on a newly prepared track. All three classes were scheduled to race but severe wind and rain prevented the 250 cc class from racing. MotoGP racing at Indianapolis is counterclockwise, with a "snake pit" complex past the start-finish line before heading down the turn one short-chute and into the infield section. The grid is composed of three columns (four for the 125 cc and 250 cc classes) and contains approximately 20 riders. Grid positions are decided in descending order of qualifying speed, with the fastest on the pole or first position. Races last approximately 45 minutes, each race is a sprint from start to finish without pitting for fuel or tyres. In 2005, a flag-to-flag rule for MotoGP was introduced. Previously, if a race started dry and rain fell, officials could red-flag (stop) the race and either restart or resume on 'wet' tyres. Now, when rain falls, a white flag is shown, indicating that riders can pit to swap the motorcycle on which they started the race for an identical one, as long as the tyres are different (that is, intermediates or slicks instead of wets)(). Besides different tyres, the wet-weather bikes have steel brake rotors and different brake pads instead of the carbon discs and pads used on the 'dry' bikes. This is because the carbon brakes need to be very hot to function properly, and the water cools them too much. The suspension is also 'softened' up somewhat for the wet weather. When a rider crashes, track marshals up the track from the incident wave yellow flags, prohibiting passing in that area; one corner farther up the track, a stationary yellow flag is shown. If a fallen rider cannot be evacuated safely from the track, the race is red-flagged. Motorcycle crashes are usually one of two types: lowside, with the rider initially following his upended bike, and the more dangerous highside, with the rider ejected ahead of the machine. Increased use of traction control has made highsides much less frequent. According to one estimate, leasing a top-level motorcycle for a rider costs about 3 to 3.5 million dollars for a racing season.〔(''THE IDIOT’S GUIDE TO MOTOGP: How to increase costs and decrease speed (Part II)'' ) SpeedTV.com Moto GP News 3 January 2006.〕 As a result of the 2008–2009 financial crisis, MotoGP is undergoing changes in an effort to cut costs. Among them are reducing Friday practice sessions, banning active suspension, launch control and ceramic composite brakes, extending the lifespan of engines, and reducing testing sessions. 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「Grand Prix motorcycle racing」の詳細全文を読む スポンサード リンク
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