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Suspension is obviously an important part of a motorcycle. It's an even more important part on an offroad machine. Proper setup can greatly increase your ability to control your machine. There are several basic concepts that should be understood before digging deeper into the mysteries of your suspension.

To start with, suspension is what allows your vehicle to "soak" up bumps. It generally allows the wheels to move independantly of the main mass of the vehicle in a more or less vertical plane. This allows, under ideal conditions, the vehicles main mass to deflect very little while the wheels move over the varied terrain.

The most basic component of your suspension is the spring. The spring supports the weight of the vehicle and rider. The more weight you place on a spring the further down in the travel the vehicle will sit. Stiffer springs require more weight to move through the same amount of travel as softer springs. Springs can be made of metals, rubber or even air bladders. The only qualifier is that they must give somewhat. Air springs and specially wound springs can give a rising rate effect.

The problem with springs is that they don't resist motion very well. A spring that is devoid of friction would bounce up and down forever if it was rapdily compressed and the compressing weight were to remain in place. To keep this perpetual bouncing in check, some form of damping should be employed. The most common form of damping is in the form of fluid being forced through small holes within the suspension components. This provides a resistance to motion. If you have ever tried to pour all the liquid out of a bottle by turning it upside down, then you have seen this in action. It takes time for the fluid to run out of the container. Without going into complicated engineering formulas, it's the same way fluid dampens the movement of suspension. Any form of friction can be used to dampen suspension. Some forms of friction are not good however. Stiction is caused when the amount of force needed to overcome the initial movement of the suspension is greater than the actual damping capabilities of the suspension. It generates a harsh initial response to suspension input. fluid on it's own has no discernable stiction, however, the seals and bushings and lateral binding forces acting on suspension components may cause stiction.

The amount of damping does not have to be a constant. It can be varied by any number of things. The fluid viscosity, damping passageway size, temperature and leverage all may effect the rate of damping. Increased or "more" damping means the motion of the suspension is slower. Quicker or "less" damping means the suspension motion speed is increased.

Spring rates may be altered by either replacing the springs, cutting the springs or adding air in conjunction with springs, or increasing the air pressure in a pure air system. Spring rate for a coil spring is measured in weight X distance travelled. For example 22kg per inch.. or 22lbs per inch. If you take a spring that has given rate you will increase that rate if you remove coils from the spring. This is because you have less coils compressing, so the remaing coils must compress more to take up a given amount of travel. Since we know that increasing the weight applied to a spring will cause it to compress more, we know that we will have a static amount of travel that the vehicle weight causes the suspension to travel through before coming to a rest. The difference between fully extended suspension and this resting sag is known as the static sag. Add a rider and the difference between fully extension and the sag point is sometimes called race sag, or working sag.

Those are the basic components of suspension. This may seem a bit basic to some, but without this basic understanding it will be impossible to follow the proceeding articles. There are several ways to go about setting up your suspension. You could approach it from a purely scientific engineering angle and come up with formulas to compute the prefect spring rates, damping rates and sag. However, you would quickly find that there is no one perfect setting that will work for every condition.

Stay tuned next time when we will get into the meat of things and cover setting and adjusting spring rates and sag.