A mountain bike or mountain bicycle (abbreviated MTB or ATB (all terrain bicycle)) is a bicycle designed for off-road cycling, including jumps, and traversing of rocks and washouts, and steep declines, either on dirt trails, logging roads, or other unpaved environments. Bicyles used for mountain biking are different from road bikes and racing bikes, because mountain bikes need to be able to withstand the impacts of off-road use and the frame geometry needs to allows for the surmounting of obstacles such as logs and rocks. Most mountain bikes use 26 inch (559 mm) bicycle wheels with wide, knobby tires for extra traction and shock absorption. Since the 2000s, front wheel suspension has become the norm and 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 sport's development 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 subtypes places different demands on the bike and the cyclist, and so high-end mountain bike companies make different designs to suit these different sports. MTBs produced in the 2000s often have a wide range of gears, giving 21 to 27 speeds, to facilitate steep hill climbing and rapid descents. Most higher-end mountain bikes produced since the mid-2000s use disc brakes instead of cantilever or V-brakes, because disc brakes offer better stopping power under extreme conditions.
The risk of injury is inherent in the sport of mountain biking, especially in the more extreme disciplines such as downhill biking, which can include drops and jumps over rocky terrain. To reduce the risk of injuries such as concussions, abrasions, and cuts, mountain bikers often wear protective equipment such as helmets, gloves, and padding. The amount of protective gear depends on the type of mountain biking and the difficulty of the course. While a cross-country rider on a flat dirt trail might only wear a road biking helmet and gloves, a downhill biker or dirt jumper will typically wear a full-face BMX-style helmet and plastic "armor" pads on the knees, elbows, chest, and back.
Riding bicycles off-road goes back to the beginning of cycling, when road racing cyclists used off-road cyclo-cross as a means of keeping fit during the winter. Cyclo-cross eventually becoming a sport in its own right in the 1940s, with the first world championship in 1950. The French Velo Cross Club Parisien (VCCP) comprised about twenty-one young cyclists from the outskirts of Paris, who between 1951 and 1956 developed a sport that was remarkably akin to present-day mountain biking.
The Roughstuff Fellowship was established in 1955 by off-road cyclists in the UK. In the early 1970's, one member of the Rough Stuff Fellowship, Geoff Apps, began developing an off-road bicycle. It eventually became a machine uniquely suited to the wet and muddy off-road conditions found in the south-east of England and was sold under the Cleland brand until 1984.
In the US, the mountain bike has its origins in the modified heavy cruiser bicycles used for freewheeling down mountain trails in Marin County, California in the mid-to-late 1970s. At the time, there were no mountain bikes. The earliest ancestors of modern mountain bikes were based around frames from cruiser bicycles such as those made by Schwinn. The Schwinn Excelsior was the frame of choice due to its geometry. Riders used balloon-tired cruisers and modified them with gears and motocross or BMX-style handlebars, creating "klunkers". The term was also be used as a verb since the term "mountain biking" was not yet in use. Riders would race down mountain fireroads, causing the hub brake 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 interest of the public. The sport originated in California on Marin county's Mount Tamalpais.
It was not until the late 1970s and early 1980s that road bicycle companies started to manufacture mountain bicycles using high-tech lightweight materials. Joe Breeze is normally credited with introducing the first purpose-built mountain bike in 1978. Tom Ritchey then went on to make frames for a company called MountainBikes which was a partnership between Gary Fisher, Charlie Kelley and Tom Ritchey. Tom Ritchey, with his skills in frame building, also built the original bikes. The company's three partners ran into rough times and finally fell apart at the 1983 trade show. The designs were basically road bicycle frames (with heavier tubing and different geometry) with a wider frame and fork to allow for a wider tire. The handlebars were also different in that they were a straight, transverse-mounted handlebar, rather than the dropped, 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 in 1983 and were copies of Tom Ritchey's frames, but they were not fillet-brazed, and were made in Japan. They were configured with 15 gears using derailleurs.
Following the growing trend in 29-inch bikes (29ers as stated above), there have been other trends in the mountain biking community involving tire size. One of the more prevalent is the new, somewhat esoteric and exotic 650B (27.5 inch) wheelsize, based on the obscure wheel size for touring road bikes. Another interesting trend in mountain bikes is outfitting dirt jump or urban bikes with rigid forks. These bikes normally use 4-5" travel suspension forks. The resulting product is used for the same purposes as the original bike. A commonly cited reason for making the change to a rigid fork is the enhancement of the rider's ability to transmit force to the ground, which is important for performing tricks. In the mid-2000s, an increasing number of mountain bike-oriented resorts opened. Often, they are similar to or in the same complex as a ski resort or they retrofit the concrete steps and platforms of an abandoned factory as an obstacle course, as with Ray's MTB Indoor Park. Mountain bike parks which are operated as summer season activites at ski hills usually include chairlifts which are adapted to bikes, a number of trails of varying difficulty, and bicycle rental facilities.
Cross country (XC) mountain bikes usually have only a small amount of front and/or rear suspension (usually 65-110 mm) and are relatively light, which is achieved via the use of lightweight materials and construction in both frame and components. As a consequence, XC bikes are often less durable than other types of mountain bikes when used outside of their intended purpose. On full-suspension XC bikes, both front and rear, is typically provided by pneumatic (air) shocks or smaller coil/oil shocks and forks. Some full-suspension XC bikes may weigh as little as 21 pounds (9.5 kg), although they still are not as popular as hardtail XC bikes. The most XC bikes have only front suspension, and are normally referred to as hardtails. This is the most used type in XC competitions. A few XC bike models have no suspension and use a rigid front fork, saving weight but relying more on rider skill to negotiate rough terrain. XC or general riding is the most popular form of mountain biking, focused on climbing and quick turning abilities rather than on the aggressive descent capabilities of freeride or single-purpose downhill mountain bikes. XC bikes reflect this in their lighter weights and steeper geometries. However, due to their lighter frames and suspension, most XC bikes are poor choices for heavy-impact activities such as jumps and high-speed traverse of large obstacles such as rocks and deep washouts.
Enduro/all-mountain (AM) bikes are generally considerably heavier than XC bikes, typically weighing between 30 and 35 pounds (14 to 16 kg). These bikes tend to feature greater suspension travel, frequently as much as 6 inches (150 mm) of front and rear travel, often adjustable on newer mid- and high-end bikes. They are designed to be able to ascend mild-to-moderate inclines and descend steep declines, though their relatively heavy overall weight limits their utility in all-day rides involving steep climbs.
Freeride (FR) mountain bikes are similar to downhill bikes, but with less emphasis on weight and more on strength. Freeride bikes tend to have up ample suspension, typically have at least 6 inches (150 mm) of travel. The components are built from stronger, consequently heavier, materials. They can be ridden uphill, but are inefficient and their moderately slack head tube angles make them difficult to maneuver while angled up a hill or traveling at a low speed. They are effective on technical downhill trails. Frame angles are typically steeper than those found in downhill bikes. This enhances maneuverability over and around small objects. Freeride bikes typically range in weight from 30 to 45 pounds (14 to 20 kg). Freeride trails are built using natural terrain features to create stunts such as dropoffs, also known as "hucks", narrow ladder bridges called "North Shores", as well as large ramps built to launch the rider into the air. The most durable freeride bikes are often too heavy and have too much suspension to be ridden uphill as comfortably as other less-sturdy models, although newer, more expensive bikes come with suspension specifically designed to make them easier to ride uphill. It is, however, quite common for freeriders to frequent lift accessed riding terrain, offered at ski resorts during the off season, or simply walk their bikes uphill, rather than riding them.
Downhill (DH) races are time trials events where riders ride courses separately, racing the clock. They can have technical sections like rockgardens as well as jumps and drops. Downhill bikes typically have seven or more inches (178 mm) of suspension travel. They are built with frames that are strong, yet light, which often requires the use of more expensive alloys. In the past few years, lighter downhill bikes have been getting below the 40lbs mark (18 kg). Due to their typically large or high gears, long, plush travel and slack geometry angles, Downhill bikes are ideal only for riding down dedicated downhill trails and race courses. Downhill bikes have the most sag of Mountain Bikes to get ample traction to go fast over bumpy trails. Head Angles are often as slack as 64 degrees.
At ski resorts that have mountain biking in the off-season, riders can get lots of runs in because of chair lifts. Shuttling up to the top of trails is very common as most trails, away from ski resorts do not have lift access. When there is no car or truck access to shuttle, riders usually push and/or ride bikes to the top of the trails. Due to the high speed nature of downhill riding most bikes only have one chain ring in the front, a large bash guard and a chain guide, though many racers are now using chain guides without bash guards to drop weight.
Trials bikes are set up very specifically for the purpose of bicycle trials. Two varieties of trials bike exist, those with 26" wheels (referred to as 'stock') and those with 20" wheels (referred to as 'mod' - because historically they were modified BMX bikes). They typically have no suspension at all, though some still make use of some form of it. Competition rules require stock bikes to have multiple gears for competition, but most riders never use their shifters. Competition rules do not require mod bikes to have any gears. Many non-competitive riders run single-speed, choosing a fairly low-speed, high-torque gear. Most modern trials bikes have no seat at all, as the rider spends all of his time out of the saddle. These bikes are significantly lighter than almost all other mountain bikes, ranging from 15 to 25 pounds (7 to 9 kg). This makes manoeuvring the bike much easier.
Dirt jumping, urban and street mountain bikes lie somewhere in between a BMX bike and a freeride bike. They are typically very strong bikes, with 4 inches (100 mm) of front suspension, and rarely any rear suspension (3 to 4 inches, 76 to 100 mm, if any), with as many as nine gears or as few as one. Tires on these bikes are usually fast-rolling, slick or semi-slicks. Dirt Jumpers usually sport a geometry of 24-26" tires, as well as a bashring (a type of bashguard) replacing the largest ring on the crankset. Dirt jumpers usually have low seatposts and oversized handlebars. Some dirt jumpers also have a detangler installed which allows the rider to spin the handle bars without tangling the brake cables.
Single-speed (SS) mountain bikes have one set gear ratio. The gear ratio chosen depends on the terrain being ridden, the strength and skill of the rider, and the size of the bike (a bike with 29" wheels often requires a different gearing than a bike with standard 26" wheels). Often single-speeds are fully rigid, steel-framed bikes. These are typically ridden by very fit individuals on mild to moderate cross country terrain.
Mountain cross or "4-cross racing" (4X) is a relatively new style of riding where four bikers race downhill on a prepared, BMX like, track, simply trying to get down first. These bikes are generally either full suspension with 3 to 4 inches (76-100 mm) of travel, or hardtails, and have, typically, quite strong frames. They run a chainguide on front and gears on the back. They have slack head angles, short chainstays and low bottom brackets to aid in cornering and acceleration.
Dual slalom (DS) is similar to mountain cross, but instead of four bikers competing together, there are just two. Courses usually have a lane for each rider, though some combine to a single lane in places or even for much of the course. The courses are in general more technical with smaller jumps compared to Mountain Cross courses and have gates. Dual Slalom races originally took place on grass slopes with gates and minimal jumps. The same bikes used in Mountain Cross are used.
Short cross or speed cross (SC) is the newest form of mountain biking. The idea is to ride short, narrow forest paths with rocks and roots, but not necessarily any ramps on them. The optimal length of the paths are from a few tens to hundreds of meters. The shortness is to provide extreme speed and thrill to get trough the hindrances as fast as possible without crashing. The altitude of each path does not have to vary much. The ultimate direction of each path from vertical aspect can be either up or down. The transitions between these essential parts are to be taken lightly and stopping at the beginning of every path is to provide maximum amount of thrilling action gained through the speed. The best fitting bicycle for SC is probably lightweight, but long travel full suspension bike.
Indycross (IX) is essentially a Mountain Cross event featuring a wide variety of features run by one competitor per time.
North Shore mountain biking originated in the steep, wet, rocky, rooty terrain of Vancouver, Canada's north shore, thus it was coined "north shore" riding. Because of the almost, if not completely impassable terrain, riders began building bridges over muddy areas, rocks, stumps and deadfall. These bridges evolved into complex, often extremely challenging, man-made stunts. Because stunts are often narrow and may require the rider to move very slowly regardless of width, north shore riding requires immense balance and bike handling skills. North shore bikes are much like freeride bikes in their geometry and downhill bikes in their component makeup. Because north shore stunts have evolved to not only include simple and complex bridges but also large drops and high speed descents through a series of stunts north shore bikes commonly have as much travel as downhill and freeride bikes, however with much more nimble and maneuverable frame designs, and often lighter-weight.
Circle dirt track racing In this class of racing any kind of bikes are used, most commonly a hard tail mountain bike with front suspension. Many different modifications are made to track racing bikes, such as reducing bike weight, increasing brake power, trying different cambers (so that when the bike leans the tire is more level with the track thus creating more grip), and trying different gear ratios.
The critical angles in bicycle geometry are the head angle (the angle of the head tube), and the seat tube angle (the angle of the seat tube). These angles are measured from the horizontal, and drastically affect the rider position and performance characteristics of the bicycle. In general, steeper angles (closer to 90 degrees from the horizontal) are more efficient for pedaling up hills and make for sharper handling. Slacker angles (leaning farther from the vertical) are preferred for high speeds and downhill stability.
In the past mountain bikes had a rigid frame and fork. In the early 1990s, the first mountain bikes with suspension forks were introduced. This made riding on rough terrain easier and less physically stressful. The first suspension forks had about 1½ to 2 inches (38 to 50 mm) of suspension travel. Forks are now available with 8 inches (203mm) of travel or more (see above under "Design.") Bikes with front suspension and rigid, non-suspended rear wheels, or hardtails became popular nearly overnight. While the hardtail design has the benefits of lower cost, less maintenance, and better pedaling efficiency, it is slowly losing popularity due to the increases in full suspension designs.
Many new mountain bikes have a "full suspension" design, meaning that both front suspension forks and some form of rear suspension are used, as opposed to front suspension only ("hard tail"). The advantages of dual suspension are increased comfort on rough terrain, and improved handling over obstacles. Disadvantages of rear suspension are increased weight, increased price, and with some designs, decreased pedaling efficiency. At first, early rear suspension designs were overly heavy, and susceptible either to pedaling-induced bobbing or lockout at certain points of the suspension arc or travel. One of the most popular rear suspension designs to solve these issues has been the 'Horst Link' which first appeared with the AMP series of bikes, and was later adopted by Specialized and many other mountain bike manufacturers.
While inexpensive department store-style mountain bikes often come with V-brakes, most higher-end mountain bikes produced since the mid-2000s use disc brakes. These offer improved stopping power over rim brakes under adverse conditions, because they are located at the center of the wheel (on the wheel hub) and therefore remain drier and cleaner than wheel rims, which are more readily soiled or damaged. While the traditional cantilever and V-brake style braking system provided ample braking for fully rigid bikes and the earlier, less sophisticated suspension fork-equipped bicycles, as suspension has evolved bicycle speeds have increased. Disc brakes offer the capacity for sustained heavy braking with fewer problems of brake fade than are encountered with rim brakes, allowing greater safety margins with less rider fatigue, greater modulation and therefore control.
The disadvantage of disc brakes is their increased cost and often greater weight. Hydraulic disc brakes, which work by moving brake fluid through a hose or line to squeeze the pads together, require much more technical maintenance but enjoy much longer service intervals than their mechanical counterparts. Mechanical disc brakes, which are simpler and somewhat less expensive, work in a similar fashion to rim brakes by pulling one pad towards the disc with a cable. The braking power of a disc brake also depends on the size of the rotor. For example, an 8-inch rotor has more stopping power than an 6-inch rotor of the same design (about 33% more). This is because the brake caliper can apply more torque with the same amount of force because the larger disc provides a longer moment arm.
Most mountain bikes use 26 in (559 mm) bicycle wheels, though some models offer 24 or 29 in (520 or 622 mm) wheels. Bicycle wheel sizes are not precise measurements, a 29 inch mountain bike wheel actually has a 622 mm (24.48 inch) bead seat diameter (the term, bead seat diameter (BSD), is used in the ETRTO tire and rim sizing system). 622 mm wheels are standard on road bikes and are commonly known as 700c. In some countries, mainly in Continental Europe, 700c (622 mm) wheels are commonly called 28 inch wheels. 24 inch wheels are used for dirt jumping bikes and sometimes on freeride bikes, rear wheel only, as this makes the bike more maneuverable. 29 inch wheels were once used for only Cross Country purposes, but are now becoming more commonplace in other disciplines of mountain biking. 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 3.00 in (60 and 76 mm) widths popular with freeride and downhill bicycles. The widest wheel widths are sometimes used by icebikers who use their mountain bikes for winter-time riding in snowy conditions.
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. Some tires can be specifically designed for use in certain weather (wet or dry) and terrain (hard, soft, muddy, etc) conditions. Other tire designs attempt to be all-around applicable. Within the same intended application, more expensive tires tend to be lighter and have less rolling resistance. Sticky Rubber tires are now available for use on freeride and downhill bikes. While these tires wear down more quickly, they provide greater traction in all conditions, especially during cornering. Tires and rims are available in either tubed or tubeless designs, with tubeless tires recently (2004) gaining favor for their pinch flat resistance. Tubeless tires can also be run at lower air pressures to improve traction and increasing rolling resistance. Popular tire manufacturers include Wilderness Trail Bikes, Schwalbe, Maxxis, Nokian, Michelin, Continental, Tioga, Kenda, Hutchinson and Panaracer.