A mountain bike or mountain bicycle (abbreviated MTB or ATB (all-terrain bicycle) 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 environments—activities 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. Most mountain bikes use wheels with rims which are 559mm in ISO sizing, colloquially referred to as “26-inch”, although the term is inaccurate as it covers too many rim and tire sizes to be meaningful. 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. Other developments include disc instead of rim brakes.
The history of the mountain bike includes contributions from 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 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 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, although in recent years, titanium 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. Throughout the 1990s and 2000s, mountain biking moved from a little-known sport to a mainstream activity.
Mountain bikes can be classified into four categories based on suspension:
Fully rigid: A frame with a rigid fork and fixed rear, no suspension.
Hardtail: A frame with a front suspension fork and no rear suspension.
Soft tail: A frame with small amount of rear suspension, activated by flex of the frame instead of pivots.
Dual or full suspension: A front suspension fork and rear suspension with a rear shock and linkage that allow the rear wheel to move on pivots.