Science Fair Project Encyclopedia
A mountain bike, mountain bicycle or ATB (All Terrain Bicycle) is a bicycle designed for riding off-road, either on dirt trails or other unpaved environments; in contrast, road bicycles aren't rugged enough for such terrain.
Mountain bikes have fat, knobby tires for extra traction. In recent years front and/or rear suspension is becoming more popular. Some Mountain bikes are also fitted with bar ends on the handlebars, but with a recent trend in riser handlebars (as opposed to a flat straight handlebar) fewer riders use bar end extensions. The bikes tend to have 26" wheels (around 2002, some models introduced 29" wheels). Most newer Mountain bikes have either 24 or 27 speeds.
In French a mountain bike is called a VTT (vélo tout-terrain: "all-terrain bicycle").
The International Mountain Bicycling Association (IMBA) is a global organization that creates, enhances, and preserves mountain bike trails. The goal of the IMBA is to help maintain sustainable mountain bike trails that work well with the environment. The IMBA also travels around the globe and teaches many smaller mountain bike organization such as MORC (Minnesota Of Road Cyclists) and ERTA (Earthriders Trails Association) how to maintain their own regions trails. Good trail maintenance is essential to the reputation and survival of mountain biking.
NORBA (National Off-Road Bicycle Association) is responsible for organizing Mountain Bike races in North America.
SORBA (Southern Off-Road Bicycle Association) is responsible for races in southeast North America.
Mountain bikes can be classified into three categories based on suspension:
- Rigid - no suspension
- Hardtail - front supension fork, no rear suspension
- Dual or Full suspension - front suspension fork and rear suspension integrated into the frame
Designs vary to reflect the challenges of the different disciplines in mountain biking:
- Cross Country (XC) Mountain Bikes tend to have only a small amount of suspension, and weigh very little. This is achieved through the use of lightweight materials and suspension is typically provided by air shocks. Most "XC" bikes weigh under 30 pounds.
- Enduro ( or "All Mountain") Bikes are generally heavier than XC bikes, and have more suspension travel. They are designed to cover long distances in comfort.
- Freeride Mountain Bikes are a step up again from Enduro bikes. They tend to have more suspension travel again, and are built from stronger, heavier materials. They are designed to be an all-rounder, able to cross distances (although not as quickly or efficiently as an XC bike) and able to take on dangerous and technical downhill trails (though not as quickly or effectively as a specialist downhill bike). Many freeride bikes more closely resemble downhill bikes and weigh as much, though they are usually designed to be easier to pedal than a downhill bike. Freeride bikes range in weight from 28 to 40 pounds.
- Downhill Mountain Bikes tend to be very heavy (over 40-50 pounds) and have a lot of suspension travel. They are very strong and (because of typically large gears and long, soft travel) are suitable only for riding down dedicated downhill trails and race courses.
- Trials Mountain Bikes that are set up very specifically for the purpose of bike trials. They typically have no suspension at all and only one gear, making them appear more like an oversized BMX bike than a conventional mountain bike. Some trials bikes have no seat at all, or a vestigial pad, as the rider spends all of their time out of the saddle.
- Dirt Jumping, Urban and Street Mountain Bikes lie somewhere in between a trials bike, a BMX bike and a freeride bike. They are typically very strong bikes, with 3-5" of front suspension, no rear suspension, and often with one just gear.
Mountain biking started to evolve in the late 1960s and early 1970s. At the time, there was no such thing as a mountain bike. The earliest ancestors of modern mountain bikes were based around frames from road cruisers such as those made by Schwinn. Riders used balloon tired beach cruisers and modified them with gears and motocross style handlebars. They would bomb (ride fast) down mountain fireroads causing the hub bearings to burn the grease inside, requiring the riders to repack the bearings. These were called "repack races" and triggered the first innovations in mountain bike technology as well as the initial intrest of the public. The sport originated in California .
It wasn't until the late 1970s and early 1980s that road bicycle companies started to manufacture mountain bicycles using high tech light weight materials. Gary Fisher is normally credited with introducing the first purpose-built mountain bike in 1979. The designs were basically road bicycle frames with a wider frame and fork to allow for a wider tire. The handlebars were also different in that they were a straight handlebar, rather than the low curved handlebars that are typically installed on road racing bicycles. Also, some of the parts on early production mountain bicycles were taken from the BMX bicycle. The first mass produced mountain bikes were produced by Specialized and had 18 gears.
Until recently, mountain bicycles had road bicycle style frames and geometry. With mountain bicycling becoming more mainstream and thus more aggressive in riding styles, newer, stronger, and better designed frames are coming out with a geometry designed for much more aggressive riding such as riding over obstacles like logs, rocks, and man-made wooden bridges and ramps. Also, many riders are now jumping on mountain bicycles and taking on a more BMX style of riding. Newer mountain bikes have either 24 or 27 speeds, with 3 gears in the front and 8 or 9 gears at the rear wheel.
Many newer mountain bikes have a full suspension design. In the past, mountain bikes had a rigid frame and a rigid fork. In the mid 1990s, mountain bikes started to have a front suspension fork. This made riding on rough terrain easier on a rider's arms. The first suspension forks had about 1½ to 2 inches (38 to 50 mm) of suspension travel. Soon after, some frame designers came out with a suspension frame which gave riders a smoother ride all around.
Early suspension frames were heavy and bounced up and down while a rider pedaled. This took a lot of power out of a rider's pedal stoke, especially during climbs up steep hills. Newer suspension frame and fork designs have improved the weight, amount of suspension travel, and feel. Many lock out the rear suspension while the rider is pedaling hard or climbing. Most suspension frames and forks have at least 4 inches (100 mm) of suspension travel. More aggressive suspension frames and forks made for downhill racing and freeriding have as much as 8 or 9 inches (200 or 230 mm) of suspension travel. Many riders still prefer to ride a hardtail frame (bicycle without a rear suspension), but almost all mountain bicycle riders use a suspension fork. Well-known suspension fork manufacturers are, for example, Manitou, Rock Shox, and RST.
Most mountain bikes use 26 in (559 mm) wheels, though some models offer 24 or 29 in (520 or 622 mm) wheels. Inch-sizes for bicycle wheels are not precise measurements - a 29 inch wheel is actually a 700c wheel, which is 622 mm, or 24.48 inches, in diameter. Wheels come in a variety of widths, ranging from standard rims suitable for use with tires in the 26 in x 1.90 in to 2.10 in (559 x 48 to 53 mm) size, to 2.35 and 2.80 in (60 and 71 mm) widths popular with freeride and downhill bicycles. Manufacturers produce a wide variety of tread patterns to suit different needs. Among the styles are slick street tires, street tires with a center ridge and outer tread, fully knobby, front-specific, rear specific, and snow studded. Tires and rims are available in either tubed or tubeless designs, with tubeless tires recently (2004) gaining favor among downhill riders for their flat resistance.
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