Mountain Bikes!
A mountain bike or mountain bicycle (abbreviated MTB or ATB (all terrain bicycle)) is a bicycle created for off-road cycling. This activity includes traversing of rocks and washouts, and steep declines, on dirt trails, logging roads, and other unpaved environments — activities usually called mountain biking. These bicycles need to be able to withstand the stresses of off-road use with obstacles such as logs and rocks. Most mountain bikes use wheels with rims which are 559mm in ISO sizing, colloquially referred to as “26-inch”, although the term is inaccurate as it covers too many rim and tire sizes to be meaningful. Wheels used on mountain bikes usually use wide, knobby tires for good traction on uneven terrain and shock absorption. In the current century 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 development of the sport 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 place different demands on the bike requiring different designs for optimal performance. MTB development has included an increase in gearing, up to 30 speeds, to facilitate both climbing and rapid descents. Other developments include disc instead of cantilever or V-brakes.
Cross country (XC)
Cross Countrymountain 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 1980’s and early 1990’s XC mountain bikes typically consisted of a lightweight steel hardtail frame with rigid forks. Throughout the 90’s XC bike evolved to incorporate lightweight aluminium frames and short travel (65 to 110mm) front suspension forks. Recently full suspension designs have become more prevalent, the use of advanced carbon fibre composites has allowed bike designers to produce full suspension designs in the sub 10kg. Full suspension bikes such as the Merida Ninety Two have been successfully used to win the World Cross Country Championships. 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 degrees. Although intended for off-road use, Cross Country mountain bike with their emphasis on lightweight are not designed for use on the most steep or severe terrain.
Trail Bikes
Trail bikes are a development of XC bikes that are generally used by recreational mountain bikers either at purpose built “Trail centres” or on natural off-road trails. They usually have around 5" (120-140mm) of travel, weigh 25-32 lbs, and have geometries slightly slacker than XC bikes, though not as slack as all-mountain (AM) bikes. 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 degrees) which provides greater stability while descending.
All-Mountain (AM)
Enduro/all-mountain (AM) bikes bridge the gap between cross-country and freeride bikes, typically weighing between 29 and 35 pounds (14 to 16 kg). 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 bike are intended to ridden on all-day rides involving steep climbs and steep descents, hence the term ‘all-mountain’.
Freeride (FR)
Freeride (FR) 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 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). 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.
Downhill (DH)
Downhill (DH) 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. 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 of the most up to date designs feature internal gearboxes built directly into the frame construction, this modification eliminates the need for the rear derailleur mechanism, although this design has not been widely embraced yet.
Trials Bikes (TB)
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 (6.8 to 11 kg). This makes maneuvering the bike much easier.
Dirt Jump Bike (DJB)
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 Mountain Bikes (SSMB)
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
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 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)
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/Speed Cross (SC)
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 through 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.
*Definitions provided by Wikipedia contributors. “Road bicycle.” Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 6 Jan. 2010. Web. 2 Mar. 2010.
