Bicycle suspension is the system, or systems, used to suspend the rider and bicycle in order to insulate them from the roughness of the terrain. Bicycle suspension is used primarily on mountain bikes, but is also common on hybrid bicycles.
Bicycle suspension can be implemented in a variety of ways, and any combination thereof: Front suspension Rear suspension Suspension seatpost Suspension saddle Suspension stem (now uncommon) Suspension hub
Bicycles with only front suspension are referred to as hardtail and bicycles with suspension in both the front and rear are referred to as dual or full suspension bikes. When a bicycle has no suspension it is called rigid. Bicycles with only rear suspension are uncommon although the Brompton folding bicycle is equipped with rear only suspension.
Although a stiffer frame is usually preferable, no material is infinitely stiff and therefore any frame will exhibit some flexing. Bicycle designers intentionally make frames in such a way that the frame itself can absorb some vibrations.
Besides providing comfort to the rider, suspension systems improve traction and safety by helping to keep one or both wheels in contact with the ground.
History
As early as 1885, the Whippet brand of safety bicycle was notable for its use of springs to suspend the frame. In 1901 the famous author on bicycles Archibald Sharp patented air suspension for bicycles. He was involved with Air Springs Ltd and they developed an air sprung motorcycle in 1909, but they also loaned an air sprung bicycle to the correspondent to show how good the suspension was.
In 1983 Brian Skinner designed and implemented the first suspension system with a simple rear shock and a single pivot called the MCR Descender. This bike had a rigid front fork as the technology to build a fork with a shock wasn't here yet, at least for a mountain bike. Front suspension first appeared on a bike in 1990 when the founder of Manitou, Doug Bradburry, designed and built the first front suspension fork in his garage. The fork used elastomers and had no dampening effect, just a spring. However, the stiffness was able to be controlled and functioned well except in cold weather.
Front suspension
Telescopic
Front suspension is often implemented using a telescopic (i.e., telescoping) fork. The specifics of the suspension depend on the type of mountain biking the fork is designed for and is generally categorized by the amount of travel. For instance, manufacturers produce different forks for cross-country (XC), downhill (DH), freeride (FR) and enduro (ND) riding which all have different demands for amount of travel, weight, durability, strength, and handling characteristics.
Telescopic suspension forks have become increasingly sophisticated. The amount of travel available has typically increased. When suspension forks were introduced, 80–100 mm of travel was deemed sufficient for a downhill mountain bike. This amount of travel is now common for cross-country disciplines, whereas downhill forks typically offer 200 mm or more of travel for handling the most extreme terrain.
Other advances in design include adjustable travel, allowing riders to adapt the fork's travel to the specific terrain (e.g. less travel for uphill or paved sections, more travel for downhill sections). Many forks feature the ability to lock out the travel. This eliminates or drastically reduces the fork's travel for more efficient riding over smooth sections of terrain. The lockout can sometimes be remotely controlled by a lever on the handlebars via a mechanical cable, or even through electronics.
As with all shock absorbers it usually consists of two parts: a spring, and a damper. The spring may be implemented with a steel or titanium coil, compressed air, or even an elastomer. Different spring materials have different spring rates which have a fundamental effect on the characteristics of the fork as a whole. Coil-sprung forks keep an approximately constant ("linear") spring rate throughout their travel. The spring rate of air-sprung forks however increases with travel, making them progressive. Titanium coils are much lighter but much more expensive. Air-sprung forks are generally lighter still.