Bicycle fork
The length of the fork is usually measured parallel to the steerer tube from the bottom of the lower bearing race to the center of the front wheel axle.
[5] The blades must be the proper length to both accommodate the desired wheel and have the correct amount of rake to provide the approximate steering geometry intended by the frame designer.
[6] 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.
Popular makers of suspension forks include Cannondale, Fox, SR Suntour, Manitou, Marzocchi, and RockShox.
When suspension forks were introduced, 80–100 mm of travel was deemed sufficient for a downhill mountain bike.
Air springs utilize the thermodynamic property of gases that their pressures increase as they are compressed adiabatically.
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.
Some have employed linkages to provide the mechanical action instead of relying upon telescoping elements.
Others, notably Cannondale use a single shock built into the steerer tube above the crown.
Another notable recent development in fork technology is the Lauf Spring which utilises composite leaf springs to provide mechanical shock absorption and damping, whilst offering a sizable weight reduction compared to conventional designs [9] Some manufacturers, such as Cannondale and Strida, offer a fork with a single leg.
These forks use linear needle roller bearings on octagonal races to transmit the steering torque to the wheel, while conventional two bladed suspension forks use tubular linear plain bearings.
Track forks traditionally have round-section blades rather than the oval section used on road bikes, partly because a round section is stiffer under the lateral forces imposed by frequent sprinting but mainly because track racing tyres are always narrow and do not require the additional clearance afforded by oval blades.
Track forks may not be drilled for a front brake if the bicycle is intended to be used only on a velodrome.
A new trend in triathlon bikes is similar, called a bayonet or external-steerer fork, but the pivot bearings are at the top and bottom of something that still resembles a head tube.
[10] Forks have been made from steel, aluminum, carbon fiber, titanium, magnesium, and various combinations.
