page_title: Bicycle fork
section_title: Suspension
hierarchical_section_title: Bicycle fork / Suspension
caption_attribution_description: English: Cannondale Headshok suspension bicycle fork
context_page_description: A bicycle fork is the part of a bicycle that holds the front wheel.
  A fork typically consists of two blades which are joined at the top by a fork crown. The crown is often at the front. Most suspension forks have an arch connecting the two side of the lowers It is often in front of the stanchions but not always. Above the crown, a steerer tube attaches the fork to the bicycle and the handlebars allowing the rider to steer the bicycle. The steerer tube of the fork interfaces with the frame via bearings called a headset mounted in the head tube.
  At the bottom of the fork, fork ends hold the wheel. Usually, either the axle is bolted to the fork, or a quick release skewer passes through a hollow axle, clamping the axle to the fork.
  The term fork is sometimes also used to describe the part of a bicycle that holds the rear wheel, which on 19th century ordinary or penny-farthing bicycles was also a bladed fork. On most modern bicycle designs the rear wheel is now attached to a rear triangle comprising the seat tube, a pair of seat stays, and a pair of chain stays, rather than an actual fork, but the rear fork usage persists.
context_section_description: On most mountain bicycles, the fork contains a set of shock absorbers, in which case the blades typically consist of upper and lower telescoping tubes and are called "legs." The suspension travel and handling characteristics vary depending on the type of mountain biking the fork is designed for. For instance, manufacturers produce different forks for cross-country (XC), downhill, and freeride riding. Forks designed for XC racing are typically lighter, less robust and have less suspension travel than those designed for rougher terrain and more extreme conditions.
  Popular makers of suspension forks include Cannondale, Fox, SR Suntour, Manitou, Marzocchi, and RockShox.
  Suspension fork design has advanced in recent years with suspension forks becoming increasingly sophisticated and diverse in design.  The amount of suspension travel available has increased over time. When suspension forks were introduced, 80–100 mm of travel was deemed sufficient for a downhill mountain bike.  Typically this amount of travel is now used in XC disciplines, with downhill forks now offering 150 to 200 mm of travel for handling extreme terrain. This is not the limit of suspension fork travel; for example, the Marzocchi Super Monster T offers 300 mm (12 inches) of travel.
  Other advances in design include adjustable travel allowing riders to adapt the fork's travel to the specific terrain profile. Typically, less suspension travel is needed for uphill or flat terrain than for downhill terrain.  Advanced designs also often feature the ability to lock out the fork to eliminate or drastically reduce the fork's travel for more efficient riding over smooth sections of terrain. This lockout can sometimes be activated remotely by a cable and lever on the handlebars.
  The shock absorber usually consists of two parts: a spring and a damper or dashpot. The spring may be implemented with a steel or titanium coil, an elastomer, or even compressed air. The choice of spring material has a fundamental effect on the characteristics of the fork as a whole.  Coil spring forks are often heavier than designs which use compressed air springs, but they are more easily designed to exhibit a linear, Hookean response throughout their travel. Replacing steel coils with titanium coils in a design can decrease the weight of the design but leads to an increase in expense.  Air springs utilize the thermodynamic property of gases that their pressures increase as they are compressed adiabatically. As the "spring" is provided by air rather than a coil of metal, forks with air springs are often lighter. This makes their use more common in XC designs. Another advantage of this type of fork design is that the spring constant can be adjusted by adjusting the air pressure. This allows a fork to be tuned to a rider's weight. One disadvantage of this design is the difficulty in achieving a linear response, as pressure varies approximately inversely (not linearly) with volume in a gas. As the fork compresses, the effective spring constant of the fork increases.  Increasing the volume of the air inside the spring can reduce this effect, but the volume of the spring is ultimately limited, as it needs to be contained within the dimension of the fork blade.
  The damper usually forces oil to pass through one or more small openings or shim stacks in the suspension fork.  On some models, the spring, the damper, or both may be adjusted for rider weight, riding style, terrain, or any combination of these or other factors. The two components may be separated with the spring mechanism in one blade and the damper in the other.
caption: Cannondale Head Shok suspension fork
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