A mountain bike or mountain bicycle (abbreviated MTB) is a bicycle created for off-road cycling. This activity includes traversing of rocks and washouts, and steep declines, on dirt trails, logging roads, and other unpaved environmentsactivities usually called mountain biking. These bicycles need to be able to withstand the stresses of off-road use with obstacles such as logs and rocks. Wheels used on mountain bikes usually use wide, knobby tires for good traction on uneven terrain and shock absorption. Since the mid-1990s, front wheel suspension has become the norm and since the late 1990s, full front and rear suspension has become increasingly common. Some mountain bikes are also fitted with bar ends on the handlebars to give extra leverage for hill-climbing. 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 gearing, up to 30 speeds, to facilitate both climbing and rapid descents. However, recently the "1 by 10" trend has emerged, simplifying the gearing to one sprocket in the front and 10 in the rear of the drive train. This allows for lighter component weights while still maintaining a large spread of gearing options. Single speed mountain bikes are also becoming more and more popular. Other developments include disc instead of rim brakes and 29" tires instead of the traditional 26" tires. The history of the mountain bike includes contributions from cyclo-cross in Europe and the Roughstuff Fellowship[1] in the UK. The name "mountain bike" first appeared in print in 1966 as "mountain bicycle". The mountain bike was a modified heavy cruiser bicycle used for freewheeling down mountain trails. The sport became popular in the 1970s in Marin county, California, USA. The 2007 documentary fi m, 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, although in recent years, titanium, hydroformed aluminium, and carbon fiber frames have become more common but can be very expensive. The first mass production mountain bike was the Specialized Stumpjumper, first produced in 1981.[2] 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. There are several different styles of mountain biking, usually defined by the terrain, and therefore bikes employed. Styles of mountain bike riding and mountain bikes have evolved rapidly in recent years leading to terms such as Freeride and "Trail bike" being used to categorise mountain bikes. Definitions for the most widely used terms are listed below. Cross country (XC) mountain bikes are designed primarily around the discipline of cross country racing. Cross country racing with its emphasis on climbing as well as speed and endurance demands bikes that are both lightweight and efficient. In the 1980s and early 1990s XC mountain bikes typically consisted of a lightweight steel hardtail frame with rigid forks. Throughout the 1990s XC bikes evolved to incorporate lightweight aluminium frames and short travel (65 to 110 mm) front suspension forks. Recently full suspension designs have become more prevalent, and the use of advanced carbon fiber composites has allowed bike designers to produce full suspension designs under 10 kg. The geometry of Cross Country bikes favours climbing ability and fast responses over descending and stability and as a result typical head angles are 7071. Although intended for off-road use, Cross Country mountain bikes with their emphasis on lightweight construction are not designed for use on the most steep or severe terrain.