Bicycle suspension refers to the system or systems used to suspend the rider and all or part of the bicycle in order to protect them from the roughness of the terrain over which they travel. Bicycle suspension are used primarily on mountain bicycles, but are also common on hybrid bicycles, and can even be found on some road bicycles.
Bicycle suspension can be implemented in a variety of ways:
Suspension front fork
Suspension stem (although these have fallen out of favor)
Suspension seatpost
Rear suspension
or any combination of the above. Bicycles with suspension front forks and rear suspensions are referred to as full suspension bikes. Additionally, suspension mechanisms can be incorporated in the seat or saddle, or the hubs.
Besides providing obvious rider comfort, suspensions improve both safety and efficiency by keeping one or both wheels in contact with the ground and allowing the rider's mass to move over the ground in a flatter trajectory.
Front suspension is often implemented with a set of shock absorbers in the front fork. 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 (DH), and freeride riding.
Suspension fork design has advanced in recent years with suspension forks becoming increasingly sophisticated. The amount of travel available has typically increased. When suspension forks were introduced 80-100mm of travel was deemed sufficient for a downhill mountain bike. Typically this amount of travel is now more normal for cross country disciplines. Downhill forks can now offer in the region of 200 to 230mm of travel for handling the most extreme terrain.
Other advances in design include adjustable travel allowing riders to adapt the forks travel to the specific terrain profile. eg less travel for uphill sections more travel for downhill sections. Advanced designs also often feature the ability to lockout the fork to completely eliminate or drastically reduce the fork's travel for more efficient riding over smooth sections of terrain. This lockout can sometime 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, however they are more easily designed to keep a linear spring rate throughout their travel. Substituting titanium coils in favor of steel coils in a design can decrease the weight of the design but leads to an increase in expense. Air springs work by utilising the characteristic of compressed air to resist further compression. As the "spring" is provided by the compressed air rather than a coil of metal they can often be made lighter; this makes their use more common in cross country designs. Another advantage of this type of fork design is that the spring rate can easily be adjusted by adjusting the pressure of the air in the spring. This allows a fork to be effectively tuned to a rider's weight. One disadvantages of this design is the difficulty in achieving a linear spring rate throughout the fork's action. As the fork compresses, the air held inside the air spring also compresses; towards the end of the fork's travel, further compression of the fork requires ever increasing compression of the compressed air with the spring. This results in an increase in spring rate. 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 leg.
The damper is usually implemented by forcing oil to pass through one or more small openings or shim stacks. 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 leg and the damper in the other.
Some manufacturers, especially Cannondale, have tried other variations including a single shock built into the steering tube above the crown and a fork with just a single leg that has a shock built into it. Others have marketed suspension forks that employ linkages to provide the mechanical action instead of relying upon telescoping elements.
Bicycle suspension can be implemented in a variety of ways:
Suspension front fork
Suspension stem (although these have fallen out of favor)
Suspension seatpost
Rear suspension
or any combination of the above. Bicycles with suspension front forks and rear suspensions are referred to as full suspension bikes. Additionally, suspension mechanisms can be incorporated in the seat or saddle, or the hubs.
Besides providing obvious rider comfort, suspensions improve both safety and efficiency by keeping one or both wheels in contact with the ground and allowing the rider's mass to move over the ground in a flatter trajectory.
Front suspension is often implemented with a set of shock absorbers in the front fork. 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 (DH), and freeride riding.
Suspension fork design has advanced in recent years with suspension forks becoming increasingly sophisticated. The amount of travel available has typically increased. When suspension forks were introduced 80-100mm of travel was deemed sufficient for a downhill mountain bike. Typically this amount of travel is now more normal for cross country disciplines. Downhill forks can now offer in the region of 200 to 230mm of travel for handling the most extreme terrain.
Other advances in design include adjustable travel allowing riders to adapt the forks travel to the specific terrain profile. eg less travel for uphill sections more travel for downhill sections. Advanced designs also often feature the ability to lockout the fork to completely eliminate or drastically reduce the fork's travel for more efficient riding over smooth sections of terrain. This lockout can sometime 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, however they are more easily designed to keep a linear spring rate throughout their travel. Substituting titanium coils in favor of steel coils in a design can decrease the weight of the design but leads to an increase in expense. Air springs work by utilising the characteristic of compressed air to resist further compression. As the "spring" is provided by the compressed air rather than a coil of metal they can often be made lighter; this makes their use more common in cross country designs. Another advantage of this type of fork design is that the spring rate can easily be adjusted by adjusting the pressure of the air in the spring. This allows a fork to be effectively tuned to a rider's weight. One disadvantages of this design is the difficulty in achieving a linear spring rate throughout the fork's action. As the fork compresses, the air held inside the air spring also compresses; towards the end of the fork's travel, further compression of the fork requires ever increasing compression of the compressed air with the spring. This results in an increase in spring rate. 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 leg.
The damper is usually implemented by forcing oil to pass through one or more small openings or shim stacks. 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 leg and the damper in the other.
Some manufacturers, especially Cannondale, have tried other variations including a single shock built into the steering tube above the crown and a fork with just a single leg that has a shock built into it. Others have marketed suspension forks that employ linkages to provide the mechanical action instead of relying upon telescoping elements.
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