Mountain bike

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A full suspension mountain bike.

A mountain bike (MTB^[1]) or mountain bicycle is a bicycle designed for off-road cycling. Mountain bikes share some similarities with other bicycles, but incorporate features designed to enhance durability and performance in rough terrain, which makes them heavy. These typically include a suspension fork, large knobby tires, more durable wheels, more powerful brakes, straight, extra wide handlebars to improve balance and comfort over rough terrain, lower gear-ratios for climbing steep grades and sometimes rear suspension to really smooth out the trail as well as dropper-posts to quickly adjust the seat height.^[2]

Mountain bikes are generally specialized for use on mountain trails, single track, fire roads, and other unpaved surfaces. Mountain biking terrain commonly has rocks, roots, loose dirt, and steep grades. Many trails have additional technical trail features (TTF) such as log piles, log rides, rock gardens, skinnies, gap jumps, and wall-rides. Mountain bikes are built to handle these types of terrain and features. The heavy-duty construction combined with stronger rims and wider tires has also made this style of bicycle popular with urban riders and couriers who must navigate through potholes and over curbs.^[3]

Since the development of the sport of mountain biking in the 1970s, many new subtypes of mountain biking have developed, such as cross-country (XC), enduro, all mountain, freeride, downhill, and a variety of track and slalom types. Each of these place different demands on the bike, requiring different designs for optimal performance. MTB development has led to an increase in suspension travel, now often up to 8 inches (200 mm), and gearing up to 36 speeds, to facilitate both climbing and rapid descents. Advances in gearing have also led to a "1x" (pronounced "one-by") trend, simplifying the gearing to one chainring in the front and a cassette at the rear, typically with 9 to 12 sprockets.

The expressions "all terrain bicycle", "all terrain bike", and the acronym "ATB" are used as synonyms for "mountain bike",^{[4][5][6][7][8]} but some authors consider them passé.^[9]

History[]

Origins[]

A cross country mountain bike race.

The original mountain bikes were modified heavy cruiser bicycles used for freewheeling down mountain trails. The sport became popular in the 1970s in Northern California, USA, with riders using older, single-speed balloon tire bicycles to ride down rugged hillsides.^[10] These modified bikes were called "ballooners"^[11] in California, "klunkers"^[12] in Colorado, and "dirt bombers"^[13] in Oregon. Joe Breeze, a bicycle frame builder, used this idea and developed what is considered the first mountain bike.^[14]

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 aluminum. The first production mountain bike available was the 1979 Lawwill Pro Cruiser.^[15] The frame design was based on a frame that Don Koski fabricated from electrical conduit and a Schwinn Varsity frame. Mert Lawwill had Terry Knight of Oakland build the frames. The bikes sold for about $500 new and were made from 1979 though 1980 (approximate run of 600 bikes).

The first mass production mountain bike was the Specialized Stumpjumper, first produced in 1981.^[16] With the rising popularity of mountain bikes, Randolph (Randy) Ross, executive vice president of Ross Bicycles Inc., was quoted in the New York Times saying I'd say these bikes are one of the biggest things that ever happened to the biking industry. Its basic look constitutes "a total shift in image" for the industry.^[17]

Throughout the 1990s and 2000s, mountain biking moved from a little-known sport to a mainstream activity complete with an international racing circuit and a world championship, in addition to various free ride competitions, such as the FMB World Tour and the Red Bull Rampage.

Technical evolution[]

The evolution of mountain bike design can be seen from the successive mid-range product lines of the major manufacturers.

Designs[]

Mountain bikes can usually be divided into four broad categories based on suspension configuration:

• Rigid: A mountain bike with large, knobby tires and straight handlebars, but with neither front nor rear suspension.
• Hard Tail: A mountain bike equipped with a suspension fork for the front wheel, but otherwise a rigid frame.
• Soft Tail: A recent addition, a mountain bike with pivots in the frame but no rear shock. the flex of the frame absorbs some vibrations. These bikes are usually cross country bikes.
• Full suspension (or dual suspension): A mountain bike equipped with both front and rear suspension. The front suspension is usually a telescopic fork similar to that of a motorcycle, and the rear is suspended by a mechanical linkage with components for absorbing shock.

Discipline-oriented designs[]

There are several different styles of mountain biking, usually defined by the terrain, and therefore the type of bicycles employed. Styles have evolved rapidly. In the earliest days, all were somewhat custom, home-built machines, and were used for any number of stunts, tricks, racing or other activities. The general design was similar. As the sport grew, more specialized designs and equipment were introduced. The further market segmentation beyond simple front suspension XC bicycles began to occur in the mid-1990s, as large bicycle and equipment manufacturers were able to cater specifically to changing demands. Today, there are a large variety of discipline oriented designs. Mountain bikes can be multi-thousand dollar machines that are purpose built for the discipline they were designed for.

Cross-country[]

These bicycles are designed primarily around the discipline of racing. Emphasis is on endurance which demands lightweight and efficient designs. In the 1980s and early 1990s, this typically consisted of a lightweight steel rigid frame and fork. Throughout the 1990s, lightweight aluminum frames and short travel (65 to 110 mm) suspension forks gained influence. Full suspension designs have since become more popular among racers and enthusiasts. The use of advanced carbon fiber composites allows designers to produce full-suspension designs under 10 kilograms (22 lb). However, hard tails and soft tails are seen quite often in this discipline as well. 700c wheels have largely replaced the original standard of 26" and now 29" wheels are taking over this discipline. Typical head angles are 67-70°, a geometry which favors climbing ability and fast responses over descending and stability. Although intended for off-road use, they are not designed for use on steep or particularly rough terrain.

Trail[]

These bicycles are a development from cross country and are generally used by recreational cyclists. They typically have 120–140 mm (5") of travel, weigh 11 to 15 kilograms (24 to 33 lb), with geometry situated somewhere between cross country and all-mountain designs. Having a slacker head angle (65-67°) provides greater stability while descending. With less of an emphasis on weight, typically they are designed to handle rougher terrain. Trail bikes are usually seen as hard tails, and full suspension frames. The frame material is usually seen using aluminum or carbon fiber but is sometimes seen using steel. They usually have either 27.5" or 29" wheels. Trail bikes also are seen as the do it all mountain bike. This is due to the fact that they climb very well and descend decently good. Because they have less suspension travel they can be used on a flat pedal trails one day and on the next they can be used to climb and descend mountains with ease.

Examples include the Giant Trance, the Trek Fuel EX, and the Specialized Stumpjumper, Giant Talon 4, Cannondale Habit.

Enduro/all-mountain[]

These bicycles bridge the gap between trail bikes and downhill bikes. Typically weight is 13 to 16 kilograms (29 to 35 lb). The frame materials are usually aluminum or carbon fiber. Features include longer full suspension designs, frequently as much as 6 or 7 inches (150 or 180 mm). The damping of the suspension is often adjustable to help with climbing and descending. Head angles are even more relaxed, ranging from 65° to as slack as 63.5°. They are designed to be able to climb decently and descend very well. These bikes are usually taken on all-day rides, hence the term 'all-mountain'. There has been a split between enduro and all-mountain designs, with the enduro placing more emphasis on descent due to the increased emphasis on timed downhill runs in racing when compared to more typical all-mountain riding, this category of mountain bikes is becoming one of the more popular disciplines (2020).

Examples include the Trek Slash and Specialized Enduro.

Downhill[]

An upgraded Downhill/Freeride bike: Specialized Bighit 2006 with 203 millimetres (8.0 in) of travel in the front and 190 millimetres (7.5 in) of travel in the back.

Typically having 8 inches (200 mm) or more of suspension travel, and extremely low, slack geometry (head angles of 62-63°). These designs set the rider in a comfortable position when descending steep trails at high speed. Due to their often high gear ratios, and soft suspension these are ideal only for riding down dedicated trails or race courses, almost universally requiring carrying uphill rather than riding. Frames are often intended for racing, and as such are required to be both extremely durable and lightweight. Designers often make use of similar materials in the construction of downhill and cross country frames and components despite their vastly different purposes, as the ultimate goal of a high strength to weight ratio is the same. More advanced frame and component designs have produced high-end designs with similar weights to average trail and all-mountain models, with an increasing expectation that complete bicycles remain below 40 lbs (18 kg) even in budget models. This advancement, along with increased speeds and forces in racing, and the use of specific frames for freeride applications, has necessitated or otherwise inspired many unique design features and advancements, many of which later find use on less aggressive designs. These aggressive designs are seen in the form of bash guards, clutch derailleurs, wide handlebars, advanced air suspension, bimetallic brake rotors, slack and long geometry. Several types of bicycle speed records have been registered using downhill bicycles.

Examples include the Trek Session and Specialized Demo.

Freeride[]

Similar to downhill, though with less emphasis on weight and more on strength. These designs feature ample suspension, having at least 7 inches (180 mm) of travel. Emphasis is on trail features with large air time such as jumps and drops. As such, they handle heavy impacts. Frames and parts are rarely made from carbon fiber due to strength and durability concerns and are instead usually made from aluminum, sacrificing marginal weight gain for more predictable material response under heavy usage. Pedaling efficiency and maneuverability are compromised when climbing. Originally, free-ride bikes sat between all-mountain and downhill in geometry, with frame angles steeper than those found in downhill and higher rider positioning, enhancing maneuverability on technical or low-speed features commonly found on "North Shore" style trails. Weights range from 14 to 20 kilograms (31 to 44 lb), with the wide variability resulting from the variety of components applicable for the purpose. Slopestyle and dirt jump bikes are included in this category by some, due to similar purposes, but the distinction in design is significant.

North shore bikes are much like free-ride 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.

Dirt jumping urban and street[]

Somewhere between bicycle motocross (BMX) and free-ride, designs are rigid or hard-tail with 3 to 4.5 inches (76 to 114 mm) of front suspension. Durable frames with low bottom brackets and short chainstays improve maneuverability. Designs often overlap with four-cross, with many frames including removable derailleur hangers and/or integrated chain tensioners to allow for single speed and multi-speed arrangements. Tires are usually 24 or 26" diameter, fast-rolling slicks or semi-slicks, with narrow casings (approx. 1.8-2.2"). Low seatposts and oversized handlebars and used to make room for tricks. Most have an extended rear brake cable installed and have no front brake, which allows the rider to spin the handle bars multiple times without tangling cables.

Slopestyle[]

A blend of dirt jump and free-ride, having the geometry similar to dirt jumpers, but with approximately 4" (100mm) of suspension travel in both the front and rear. These bikes are mostly used by professional slope-style riders, this specific usage being their origin, and as such are designed for the extremely large jumps and high speeds encountered in competition. The frames are either adapted from existing all-mountain or free-ride designs or designed specifically for the purpose, with durable frame designs and sophisticated suspension linkages to make the most of their minimal suspension travel. These bikes usually have relatively slack head angles, relative to their short suspension travel, with a slightly more aggressive overall geometry than the dirt jumpers many are based on. These bikes are often equipped with a mix of dirt jump and all-mountain interface specifications (headset size, bottom bracket style, rear axle width and diameter, rear derailleur hanger) to accommodate both free-ride and dirt Jump components as necessary to handle the high speeds and harsh impacts associated with their use. Slope-style bikes are also used for light downhill or trail riding by many, if not riding jumps on the same scale as professional riders, with their durability and sophisticated suspension designs allowing for extra versatility when compared to dirt jump bikes.

Mountain cross or "four-cross" (4X) is a type of racing in which four bikers race downhill on a prepared, BMX style track. These bikes generally fall under the categories of dirt jump or slope-style designs, with the main distinctions being the use of a derailleur rather than a single speed setup, or slightly slacker head angles than ordinary dirt jump bikes for increased stability at race speeds. Four-dross racing has fallen in popularity recently, with the Union Cycliste Internationale (UCI) removing four-cross from the World Cup due to excessive erosion and inconvenience caused by the purpose-built race tracks. (Four-cross bikes mostly use derailleurs while dirt jumpers usually use single speed setups.

Dual slalom (DS) is similar to four-cross, but instead of four competing cyclists during a race, there are only two, racing in parallel lanes. 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 racers will usually use dirt jump, slope-style, or dirt jump bikes. Indycross (IX) is essentially a mountain cross event featuring a wide variety of features run by one competitor at a time.^[18]

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 her time out of the saddle, and trials riding is not conducive to the use of the saddle as a control interface as in normal mountain biking. 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.

A simple dirt jump bike.

Single-speed[]

The single 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 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.

Gravel cycling[]

Gravel cycling started in the USA where they have a huge amount of space with a lot of long fire roads. Gravel cycling evolved from riders riding these long stretches of gravel and fire roads. The sport bridges the gap between road and mountain biking where riding at the speeds and efficiency of road cycling meets the ability and freedom to ride on rough and loose terrain.

Gravel bikes at first glance look very similar to road bikes with their lack of suspension, thin tyres, and drop bars. Where gravel bikes differ from road bikes is that the bars are usually wider, geometry is adapted to be more comfortable riding offroad for long periods of time and modern gravel bikes will also feature a 1x drivetrain removing the front derailleur. Wheels are also often wider and forks and rear triangle will allow for much wider tyres to cope with the terrain and requirements of riding off-road. ^[19]

Modern designs[]

A 2002 rigid 21 speed Trek 800 Sport

Gears[]

Since the 1980s,^[20][21] mountain bikes have had anywhere from 7 to 36 speeds, with 1 to 3 chain-rings on the crankset and 4 to 12 sprockets in the cogset. 30-speed, 33-speed and 36-speed mountain bikes were originally found to be unworkable, as the mud-shedding capabilities of a 10-speed, 11-speed or 12-speed cassette, and the intricacies of a 10-speed, 11-speed or 12-speed rear derailleur were originally not found to be suitable combined with front shifters, although 10, 11 and 12 speed cassettes are now commonplace in single front chainring bicycles, and are also found on some mountain bikes. However, many pro-level mountain bikers have taken to using a narrower 10-speed road chain with a 9-speed setup in an effort to reduce the weight of their bike. In early 2009, component group SRAM announced their release of their XX groupset, which uses a 2-speed front derailleur, and a 10-speed rear derailleur and cassette, similar to that of a road bike. Mud-shedding capabilities of their 10-speed XX cassette are made suitable for MTB use by extensive computer numerical control (CNC) machining of the cassette. Due to the time and cost involved in such a product, they were only aimed at top-end XC-racers. However, 10-speed has become the norm by 2011 and the market leader Shimano even offers its budget groupset "Alivio" in a 10-speed version.^[22] In July 2012, SRAM announced a 1x11 drivetrain called XX1 that does not make use of a front derailleur for lighter weight and simplicity.^[23] In the 2014 Commonwealth Games at Glasgow all leading riders used 1x11 drivetrains. SRAM's new 1x12 gearing was introduced in 2016 as SRAM Eagle. This gives a single chain ring bike better ability to climb.

Sram Eagle 1x12 Drive Train

Today in 2020, there are many different options for a mountain bikes gear set up. There are multiple companies that have hit the market with a dedicated mountain bike drive train. These companies are Shimano, Sram, Box Components, and many more. The biggest ones in the industry are Shimano and Sram. Most Mountain bikes have now a 1x11 or 1x12 drive train or gear ratios. Sram was first to introduce the 1x12 system in 2016 with their Sram Eagle system. Following behind them, in 2019 Shimano introduced their own 1x12 system called the M9000 series or 1x12 XTR system. These companies have even made specific drive trains for the different disciplines of mountain bikes. The main difference between the disciplines are weight, durability, and cost.

Geometry[]

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. Mountain bike geometry will often feature a seat tube angle around 73 degrees, with a head tube angle of anywhere from 60-73 degrees. The intended application of the bike affects its geometry very heavily. 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.

Suspension[]

A full suspension mountain bike

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 front suspension forks had about 11⁄2 to 2 inches (38 to 50 mm) of suspension travel. Once suspension was introduced, 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 improvements in full suspension designs. Front fork suspensions are now available with 8 inches (200 mm) of travel or more (see above under Designs.)

Many new mountain bikes integrate a "full suspension" design known as dual suspension, meaning that both the front and rear wheel are fitted with a shock absorber in some form as the wheel attaches to the bike. This provides a smoother ride as the front and rear wheels can now travel up and down to absorb the force of obstacles striking the tires. Dual suspension bikes of a similar quality are considerably more expensive, but this price increase brings an enormous off-road performance upgrade as dual suspension bikes are much faster on downhill and technical/rough sections, than other forms of the mountain bike. This is because when the wheel strikes an obstacle its tendency is to bounce up. Due to some forward energy being lost in the upward movement some speed is lost. Dual suspension bikes solve this problem by absorbing this upward force and transmit it into the shocks of the front and rear wheels, drastically decreasing the translation of forward momentum into useless upward movement. Disadvantages of rear suspension are increased weight, increased price, and with some designs, decreased pedaling efficiency, which is especially noticeable when cycling on roads and hard trails. At first, early rear suspension designs were overly heavy, and susceptible either to pedaling-induced bobbing or lockout.

Disc brakes[]

A front disc brake, mounted to the fork and hub

Most new mountain bikes use disc brakes. They offer much improved stopping power (less lever pressure is required providing greater braking modulation) over rim brakes under all conditions especially adverse conditions, because they are located at the center of the wheel (on the wheel hub). They therefore remain drier and cleaner than wheel rims, which are more readily soiled or damaged. The disadvantage of disc brakes is their increased cost and often greater weight. Disc brakes do not allow heat to build up in the tires on long descents; instead, heat builds up in the rotor, which can become extremely hot. There are two different kinds of disc brakes: hydraulic, which uses oil in the lines to push the brake pads against the rotors to stop the bike. They cost more but work better. Mechanical, which uses wires in the lines to pull the pads against the rotors.

Wheel and tire design[]

Typical features of a mountain bike are very wide tyres. The original 26 inch wheel diameter with ~2.125" width (ISO 559 mm rim diameter) is increasingly being displaced by 29 inch wheels with ~2.35" width (ISO 622 mm rim diameter), as well as the 27.5 inch wheel diameter with ~2.25 widths (ISO 584 mm rim diameter). Mountain bikes with 24 inch wheels are also available, sometimes for dirt jumping, or as a junior bike.^[24]

Bicycle wheel sizes are not precise measurements: a 29-inch mountain bike wheel with a 622 millimetres (24.5 in) bead seat diameter (the term, bead seat diameter (BSD), is used in the ETRTO tire and rim sizing system), and the average 29" mountain bike tire is (in ISO notation) 59-622 corresponds to an outside diameter of about 29.15 inches (740 mm).^[24]

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] 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. A mountain bike with 29" wheels is often referred to as a 29er, and a bike with 27.5 inch wheels is called a 27.5 mountain bike or as a marketing term ″650B bike″.^[24]

Wheels come in a variety of widths, ranging from standard rims suitable for use with tires in the 1.90 to 2.10 in (48 to 53 mm) size, to 2.35 and 3.00 in (60 and 76 mm) widths popular with freeride and downhill bicycles. Although heavier wheelsets are favored in the freeride and downhill disciplines, advances in wheel technology continually shave weight off strong wheels. This is highly advantageous as rolling weight greatly affects handling and control, which are very important to the technical nature of freeride and downhill riding.

A fat tire bicycle

The widest wheel/tire widths, typically 3.8 in (97 mm) or larger, are sometimes used by icebikers who use their mountain bikes for winter-time riding in snowy conditions.

Manufacturers produce bicycle tires with a wide variety of tread patterns to suit different needs. Among these 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.

Tires also come with tubes, tubeless and tubeless-ready. Tires with tubes are the standard design and the easiest to use and maintain. Tubeless tires are significantly lighter and often have better performance because you can run them at a lower tire pressure which results in better traction and increasing rolling resistance. Tubeless-ready tires are tires that can use tubes or go tubeless. A liquid sealant is used without the tube to secure the seal to the rim.^[25] Popular tire manufacturers include Wilderness Trail Bikes, Schwalbe, Maxxis, Nokian, Michelin, Continental, Tioga, Kenda, Hutchinson, Specialized and Panaracer.

Tandems[]

A tandem, full-suspension mountain bike

Mountain bikes are available in tandem configurations. For example, Cannondale and Santana Cycles offer ones without suspension, while Ellsworth, Nicolai, and Ventana manufacture tandems with full suspension.

See also[]

Media related to Mountain bikes at Wikimedia Commons

References[]