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A mountain bike or mountain bicycle (abbreviated MTB; or ATB, for all-terrain bicycle) is a bicycle created for off-road cycling. Mountain bikes are typically ridden on mountain trails, fire roads, logging roads, single tracks and other unpaved environments. These types of terrain commonly include rocks, washouts, ruts, loose sand, loose gravel, roots, and steep grades (both inclines and declines). Mountain bikes are built to handle this terrain and the obstacles that are found in it like logs, vertical drop offs, and smaller boulders. Mountain bike construction differs from a typical bicycle in many ways. The most noticeable differences are the inclusion of suspension on the frame and fork, larger knobby tires, more durable heavy duty wheels, more powerful brakes, and lower gear ratios needed for steep grades with poor traction. Since the development of the sport in the 1970s many new subtypes of mountain biking have developed, such as cross-country (XC) biking, all-day endurance biking, Freeride-biking, downhill mountain biking, and a variety of track and slalom competitions. Each of these place different demands on the bike requiring different designs for optimal performance. MTB development has included an increase in suspension, typically up to 8" or 203mm, and gearing, up to 30 speeds, to facilitate both climbing and rapid descents. However, advancements in sprocket design has recently led to the "1x (pronounced one by)" trend, simplifying the gearing to one Chainring/Sprocket in the front and multiple sprockets on the rear of the drive train, more commonly, 9, 10 or 11 speed. ==History== (詳細はcyclo-cross in Europe and the Roughstuff Fellowship in the UK. The name "mountain bike" first appeared in print in 1966 as "mountain bicycle". The original mountain bikes were modified heavy cruiser bicycles used for freewheeling down mountain trails. The sport became popular in the 1970s in Northern California, USA with riders using older single speed balloon tire bicycles to ride down rugged hillsides. Joe Breeze, a bicycle frame builder, used this idea and developed what is considered the first mountain bike. The 2007 documentary film, ''Klunkerz: A Film About Mountain Bikes'', looks at this period of off-road cycling in detail. However, it was not until the late 1970s and early 1980s that road bicycle companies started to manufacture mountain bicycles using high-tech lightweight materials, such as M4 aluminium. The first mass production mountain bike was the Specialized Stumpjumper, first produced in 1981. Throughout the 1990s and 2000s, mountain biking moved from a little-known sport to a mainstream activity complete with an international racing circuit and a world championship. 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「mountain bike」の詳細全文を読む スポンサード リンク
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