Mountain biking is a sport which consists of riding bicycles off-road, often over rough terrain, using specially adapted mountain bikes. Mountain bikes share similarities with other bikes, but incorporate features designed to enhance durability and performance in rough terrain.
This individual sport requires endurance, core strength and balance, bike handling skills, and self-reliance. XC type mountain biking generally requires a smaller range of skills but a higher level of fitness than other types of mountain biking. Advanced riders pursue steep technical descents and, in the case of freeriding, downhilling, and dirt jumping, aerial maneuvers off of specially constructed jumps and ramps.
Mountain biking can be performed almost anywhere from a back yard to a gravel road, but the majority of mountain bikers ride off-road trails, whether country back roads, fire roads, or singletrack (narrow trails that wind through forests, mountains, deserts, or fields). There are aspects of mountain biking that are more similar to trail running than regular bicycling. Because riders are often far from civilization, there is a strong ethic of self-reliance in the sport. Riders learn to repair their broken bikes or flat tires to avoid being stranded miles from help. Many riders will carry a backpack, including a water bladder, containing all the essential tools and equipment for trailside repairs, and many riders also carry emergency supplies in the case of injury miles from outside help. This reliance on survival skills accounts for the group dynamics of the sport. Club rides and other forms of group rides are common, especially on longer treks. A combination sport named mountain bike orienteering adds the skill of map navigation to mountain biking.
Downhill mountain bikes are heavier and pricier than their counterparts, cross country mountain bikes. Typically weighing 30 to 50 pounds, priced at $1,800 to $5,000, downhill mountain bikes are designed with slacker head angles (read a more upright riding position) meant to tilt the rider's mass rearward, away from the slope of the hill. Handlebars are low and relatively flat, reminiscent of motocross bikes. Dual, long-travel suspension is the norm, as are thick and wide, soft tires, for better rebounding. Also the forward crank is festooned with chain guides rollers to keep the chain on the cranks and sprockets and the rider bombs away downhill at high speeds and over large obstacles.
Modern-day downhill mountain bikes are equipped with disc rather than pad brakes. Hydraulic lines rather than cables are the norm, for better leverage and braking modulation. Given their weight, frame geometry, and lack of clipless pedals, downhill mountain bikes are bikes you're going to have much fun riding uphill.
The style and level of protection worn by individual riders varies greatly and is affected by many factors including terrain, environment, weather, potential obstacles on the trail, experience, technical skill, fitness, perceived risk, desired style and others too numerous to mention. A cross-country helmet and simple long fingered gloves are a good minimum for the majority of riding.
Limb protection becomes important when speeds rise, surfaces become loose and sketchy, terrain technical and crashes more common and more severe. Full-face helmets and armored suits or jackets are more suited to "gravity" and "air"-orientated disciplines which use jumps and drops, where their extra bulk and weight is outweighed by the bigger and more frequent crashes with worse consequences. Still, within XC community, the typical road-racing attire is what most riders use. Whatever protection is used it should fit well, be comfortable (or it won't be worn) on the bike as well as in the shop and suited for the particular type of riding. Gloves can offer increased comfort while riding, by alleviating compression and friction, and protection in the event of strikes to the back or palm of the hand or when putting the hand out in a fall. Gloves also protect the hand, fingers, and knuckles from abrasion on rough surfaces such as concrete.
Cross-Country (XC) is the most popular form of mountain biking, and the standard for most riders. It generally means riding point-to-point or in a loop including climbs and descents on a variety of terrain. A typical XC bike weighs around 9-13 kilos (20-30 lbs), and has 0-125 millimeters (0-5 inches) of suspension travel front and sometimes rear.
Downhill (DH) is, in the most general sense, riding mountain bikes downhill. The rider usually travels to the point of descent by other means than cycling, such as a ski lift or automobile, as the weight of the downhill mountain bike often precludes any serious climbing. While cross country riding inevitably has a downhill component, Downhill (or DH for short) usually refers to racing-oriented downhill riding. Downhill-specific bikes are universally equipped with front and rear suspension, large disc brakes, and use heavier frame tubing than other mountain bikes. Because of their extremely steep terrain (often located in summer at ski resorts), downhill courses are one of the most extreme and dangerous venues for mountain biking. They include large jumps (up to and including 12 meters (40 feet)), drops of 3+ meters (10+ feet), and are generally rough and steep top to bottom. To negotiate these obstacles at race speed, racers must possess a unique combination of total body strength, aerobic and anaerobic fitness, and mental control. Minimum body protection in a true downhill setting is knee pads and a full face helmet with goggles, although riders and racers commonly sport full body suits to protect themselves. Downhill bikes now weigh around 16-20 kilos (35-45 lbs), while professional downhill mountain bikes can weigh as little as 15 kilos (33 lbs), fully equipped with custom carbon fibre parts, air suspension, tubeless tires and more. Downhill frames get anywhere from 170-250 millimeters (7 to 10 inches) of travel and are usually mounted with a 200 millimeter (8 inch) travel dual-crown fork.
Four Cross/Dual Slalom (4X) is a sport in which riders compete either on separate tracks, as in Dual Slalom, or on a short slalom track, as in 4X. Most bikes used are light hard-tails, although the last World Cup was actually won on a full suspension bike. The tracks have dirt jumps, berms, and gaps. Professionals in gravity mountain biking tend to concentrate either on downhill mountain biking or 4X/dual slalom because they are very different. However, some riders, such as Cedric Gracia, still do 4X and DH, although that is becoming more rare as 4X takes on its own identity.
Freeride, as the name suggests is a 'do anything' discipline that encompasses everything from downhill racing without the clock to jumping, riding 'North Shore' style (elevated trails made of interconnecting bridges and logs), and generally riding trails and/or stunts that require more skill and aggressive techniques than XC. Freeride bikes are generally heavier and more amply suspended than their XC counterparts, but usually retain much of their climbing ability. It is up to the rider to build his or her bike to lean more toward a preferred level of aggressiveness. "Slopestyle" type riding is an increasingly popular genre that combines big-air, stunt-ridden freeride with BMX style tricks. Slopestyle courses are usually constructed at already established mountain bike parks and include jumps, large drops, quarter-pipes, and other wooden obstacles. There are always multiple lines through a course and riders compete for judges' points by choosing lines that highlight their particular skills. A "typical" freeride bike is hard to define, but 13-18 kilos (30-40) lbs with 150-250 millimeters (6-10 inches) of suspension front and rear.
Dirt Jumping (DJ) is one of the names given to the practice of riding bikes over shaped mounds of dirt or soil and becoming airborne. The idea is that after riding over the 'take off' the rider will become airborne, and aim to land on the 'landing'. Dirt jumping can be done on almost anything but the bikes are generally smaller and more maneuverable hardtails so that tricks e.g. backflips, are easier to complete. The bikes are simpler so that when a crash occurs there are fewer components to break or cause the rider injury.