lip the way back machine switch. In what seems like the not-so-distant past, it wasn't uncommon for drag racers to swap the front shocks for something that was either worn out or had the fluid drained. Out back something stiff from a big, heavy car was often used. Today, shock absorbers are available in countless configurations. They range from simple, inexpensive single adjustable models all the way up to three way or electric adjustable shocks. With today's shocks, one is given the opportunity to control the wheel motion. In turn, one can pretty much control the dynamics of the racecar.

Let's Start At The Beginning...

What really is a shock and what does it do? AFCO explains, "A shock is a hydraulic device that dampens or resists chassis movement by passing fluid (oil) through a set of orifices and valved passages. In an adjustable shock, manipulating the fluid movement through the valving of the shock changes the dampening characteristics - basically softness and stiffness. The range of softness to stiffness is an important consideration when evaluating the quality of a shock absorber. A shock with a broad adjustment range will give more for the buck, because a broad adjustment range will give more opportunity to find the optimum setting for the chassis."

"Rebound is the shock's resistance to being pulled apart. It can be used to control chassis separation, the point at which the axle housing is pushed away from the chassis and the tires are applied to the track. During separation, many things occur. Vector forces push up and forward -- and the axle housing sees the opposite force (remember that the tire sidewalls also wrap up). As the car moves forward, torque is created as the tires create traction to start this movement. Excessive separation can lead to some undesirable side effects. For example, wheel hop can occur as the tire tries to return to its original form (the tire unwraps). Stiffening the rebound can control wheel hop. Tire shake

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is similar to wheel hop and can be addressed similarly. As a rule of thumb, a bad or 'bald' starting line will require a softer rebound setting to apply the tires with more force. A good starting line can use a stiffer setting, as inherent traction exists and a stiffer rebound setting provides quicker vehicle reaction times; excessive separation only wastes time and energy."

"Compression (bump) is the shock's resistance to the chassis moving down or the axle housings moving up or into the chassis. The compression adjustment is an important setting, as it determines how long the tires are held down on the track after chassis separation. When a soft rebound is selected, a rule of thumb seems to be to use a slightly stiffer compression setting, so as to control the rebound of the tire. Track testing can determine the correct setting."

So Far So Good...

Where does one begin? It all depends upon how sophisticated the car is and how deep your pockets are. At the very least, a racecar should be equipped with a shock that allows basic valving changes. A good example of this is something like the three-way adjustable Competition Engineering shock absorber.