Mountain bike


A mountain bike 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 often makes them heavier, more complex and less efficient on smooth surfaces. These typically include a suspension fork, large knobby tires, more durable wheels, more powerful brakes, straight, wide handlebars to improve balance and comfort over rough terrain, and wide-ratio gearing optimized for topography, application and a frame with a suspension mechanism for the rear wheel. Rear suspension is ubiquitous in heavier-duty bikes and now common even in lighter bikes. Dropper seat posts can be installed to allow the rider to quickly adjust the seat height.
Mountain bikes are generally specialized for use on mountain trails, single track, fire roads, and other unpaved surfaces. In addition to being used to travel and recreate on those surfaces, many people use mountain bikes primarily on paved surfaces; some may prefer the upright position, plush ride, and stability that mountain bikes often have. Mountain biking terrain commonly has rocks, roots, loose dirt, and steep grades. Many trails have additional technical trail features 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.
Since the start of the sport in the 1970s, many new subtypes of mountain biking have been developed, such as cross-country, trail, all-mountain, enduro, 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, and gearing up to 13 speed, to facilitate both climbing and rapid descents. Advances in gearing have also led to the ubiquity of "1x" drivetrains, simplifying the gearing to one chainring in the front and a wide range cassette at the rear, typically with 9 to 12 sprockets. 1x gearing reduces overall bike weight, increases ground clearance, and greatly simplifies the process of gear selection, but 2- or 3-ring drivetrains are still common on entry-level bikes.
The expressions "all terrain bicycle", "all terrain bike", and the acronym "ATB" are used as synonyms for "mountain bike", but some authors consider them passé.

History

Origins

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, US, with riders using older, single-speed balloon tire bicycles to ride down rugged hillsides. These modified bikes were called "ballooners" in California, "klunkers" in Colorado, and "dirt bombers" in Oregon. Joe Breeze, a bicycle frame builder, used this idea and developed what is considered the first mountain bike.
Road bicycle companies did not manufacture mountain bicycles using high-tech lightweight materials like M4 aluminum until the late 1970s and early 1980s. The first production mountain bike available was the 1979 Lawwill Pro Cruiser. 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.
The first mass production mountain bike was the Specialized Stumpjumper, first produced in 1981. With the rising popularity of mountain bikes, Randolph 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.
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.

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.
  • Hardtail: 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 : 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.

    Modern designs

Gears

Since the 1980s, mountain bikes have had anywhere from 7 to 36 speeds, with 1 to 4 chain-rings on the crankset and 5 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 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. In July 2012, SRAM announced a 1×11 drivetrain called XX1 that does not make use of a front derailleur for lighter weight and simplicity. In the 2014 Commonwealth Games at Glasgow all leading riders used 1×11 drivetrains. SRAM's new 1×12 gearing was introduced in 2016 as SRAM Eagle. This gives a single chain ring bike better ability to climb.

Geometry

The critical angles in bicycle geometry are the head angle, and the seat tube angle. 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 to 73 degrees. The intended application of the bike affects its geometry very heavily. In general, steeper angles are more efficient for pedaling up hills and make for sharper handling. Slacker angles are preferred for high speeds and downhill stability.

Suspension

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 1 to 2 inches 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 of travel or more
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

Most modern mountain bikes use disc brakes. They offer considerably improved stopping power over rim brakes under all conditions especially adverse conditions, because they are located at the center of the wheel. 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 main types of mountain bike disc brakes: mechanical disc brakes and hydraulic disc brakes.
Mechanical disc brakes use a brake cable housed in a brake housing, which connects the brake lever to the brake caliper. When the lever is pulled, it tightens the cable, which in turn actuates the caliper and presses the brake pads against the rotor.
Hydraulic disc brakes, on the other hand, use a sealed hydraulic system instead of a cable. When the brake lever is pulled, it pressurizes the in-compressible brake fluid, which forces the brake pistons to move the pads against the rotor. Hydraulic systems generally provide stronger and more consistent braking performance compared to mechanical brakes.