Discipline-oriented designs of Bike

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) : Cross country 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 70–71°. 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.

Trail Bike: TrailBikes are a development of XC bikes that are generally used by recreational mountain bikers either at purpose built "Trail centers" or on natural off-road trails. They usually have around 5" (120–140 mm) of travel, weigh 11 to 15 kilograms (24 to 33 lb), and have geometries slightly slacker than XC bikes, though not as slack as AM bikes. Examples include the Giant Trance, the Trek Fuel EX series, the Specialized Stumpjumper FSR, and others. With less of an emphasis on weight, Trail Bikes are typically built to handle rougher terrain than dedicated XC bikes while having slacker head angles (69-68°) which provides greater stability while descending.

Enduro/all-mountain (AM) bikes: Enduro/all-mountain bikes bridge the gap between cross-country and freeride bikes, such as the Trek Remedy series, Specialized enduro, typically weighing between 13 to 16 kilograms (29 to 35 lb). These bikes tend to feature greater suspension travel, frequently as much as 6 inches (150 mm) or 7" of front and rear travel, often adjustable on newer mid- and high-end bikes. They are designed to be able to climb and descend well, these bikes are intended to be ridden on all-day rides involving steep climbs and steep descents, hence the term 'all-mountain'.

Downhill (DH) bikes: Downhill bikes typically have eight or more inches (200 mm) of suspension travel. They are built with frames that are strong, yet light, which often requires the use of more expensive alloys and very recently, carbon fiber. In the past few years, lighter downhill bikes have been getting below the 40 lbs 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 63 degrees. Several types of bicycle speed records have been registered downhill. 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 reduce weight. Some manufacturers have experimented with designs featuring internal gearboxes built directly into the frame construction. This modification eliminates the need for the rear dérailleur mechanism but has not been embraced due to durability issues with the gearbox during the stresses of a DH race.

Freeride (FR) mountain bikes: Freeride mountain bikes are similar to downhill bikes, but with less emphasis on weight and more on strength. Freeride bikes tend to have ample suspension and typically have at least 7 inches (180 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 14 to 20 kilograms (31 to 44 lb). 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.

Trials bike: 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 7 to 11 kilograms (15 to 24 lb). This makes maneuvering the bike much easier.

Dirt jumping, urban and street mountain bike: 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 to 6 inches (100 to 150 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. Most dirt jumpers have an extended rear brake cable installed and have no front brake, which allows the rider to spin the handle bars without tangling the brake cables.

Single-speed (SS) mountain bike: 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 "Four-cross" (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 to 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 Four-cross, but instead of four competing cyclists during a race, there are only 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 than Four-cross courses. Dual Slalom races originally took place on grass slopes with gates and minimal jumps, but are now held on man-made courses. Dual slalom riders will usually use the same bikes that Four-cross riders use.

Indycross (IX) is essentially a Mountain Cross event featuring a wide variety of features run by one competitor per time.

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.

It should be noted that in the early days of mountain biking, all mountain bikes were somewhat custom, home-built machines, and were used for any number of stunts, tricks, racing or other activities. The general design of the bikes were similar. As the sport grew, more specialized designs and equipment were introduced. The further market segmentation beyond simple front suspension XC began to occur in the mid-1990s, as large bicycle and equipment manufacturers were able to cater specifically to changing demands.