In our race car, the shocks and the springs resist compression or bump at any one corner of the car. When that same corner tries to return to its normal height, the spring promotes that motion and the shock resists. The control of these two motions, compression (bump) and rebound (droop), is the primary function of the shocks.

Compression and Rebound

The compression control side of a shock resists: 1. the bump movement of a corner of the car when a driver hits bumps (rises in the track); 2. the movement due to the transfer of weight to the front end during braking/deceleration; 3. the movement due to the transfer of weight to the rear upon acceleration; and 4. the tendency of the body to roll when the lateral forces are applied as we deviate from a straight line and turn left.

The rebound control side of the shock dynamics resists the following: 1. rear chassis rebound vertical movement caused by deceleration on entry; 2. front chassis rebound movement on acceleration; and 3. left-side rebound vertical movement caused by weight transfer and lateral loading as we negotiate the turns.

The amount of resistance that each movement, compression and rebound, generates does increase with the speed at which the shock is forced to move. Low speeds create low resistance and high-speed movement creates higher resistance. So we have two areas related to resistance: low speed and high speed.

Low-Speed Control

Low-speed shock movement is defined as shaft speeds that are between 1 to 10 inches of movement per second. These lower speeds are mostly associated with suspension movement caused by chassis roll and possibly chassis dive at turn entry where the sudden loss of speed is moderate. The low-speed control dictates much of the handling side of the shock design and racetrack performance gains related solely to chassis balance and weight redistribution.

Each shock has a piston mounted on the end of the shaft, and one or more small holes in the piston allow fluid inside of the shock to flow from one side of the piston to the other. The size of the "bleed" holes regulate how quickly the fluid will flow back and forth, and that is how the different levels of resistance are created for low-speed control. All low-speed adjustments on shocks built with that adjustment capability work by changing the size of the bleed opening to control the amount of flow.

High-speed Control

As we experience the greater velocities of shaft movement, we go into what is called high-speed control with shaft velocities from 10 to 25 inches of movement per second. The types of suspension movement that cause the higher shaft speeds in our shocks are: 1. bumps or holes in the racing surface (creating very high shaft speeds); 2. the driver stabbing the brakes on entry and hard on the throttle on exit; or 3. a sudden change in banking angle such as transitioning from banking onto the apron of the racetrack.