ANDRA FASTLANE ANDRA FASTLANE ED23 | Page 22

22 fastlane fast FIGURING OUT DRAG RACE AND STREET-STRIP SHOCK ABSORBERS The shock absorber is a key ingredient in making a car “work” on the street or on the strip. The reason for this is simple: if you can control the wheel motion, then you can control the dynamics of the car. In the world of acceleration, this boils down to “hook.” It also means your tuning capabilities are greatly expanded. Shock Basics Let’s start at the beginning. A shock is a hydraulic device that resists chassis movement by passing oil through a set of orifi ces and valved passages. A shock extends and compresses as the car moves – in the shock world, these movements are termed rebound and bump. Rebound (extension) 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. As the car is pushed up and forward, the axle housing sees the opposite force (don’t forget the tire sidewalls are also wrapping up). As the car moves forward, torque is created as the tires get traction. Too much body separation can lead to some undesirable side eff ects: • Wheel hop can occur as the tire tries to return to its original form (the tire unwraps). Stiff ening the shock’s rebound can control wheel hop. • Tire shake is similar to wheel hop and can be addressed similarly. For the most part, a “bald” starting line or unprepared surface will mandate a softer rebound setting to apply the tires with more force. A stiff er rebound setting on a well-prepped track can provide quicker vehicle reaction times. Essentially, too much separation is an ET and energy waster. Bump (compression) is the shock’s resistance to the chassis moving down or the axle housing moving up or into the chassis. The bump adjustment is important since it determines how long the tires are held down on the track after chassis separation. When you use a soft rebound setting on a double adjustable shock, try using a slightly stiff er compression setting. To get a grasp of what this is all about, pretend that you drive your car over a good old-fashioned speed bump. The speed bump “bumps” the shock and compresses it. After you drive over the speed bump, the shock rebounds and extends. That’s where you get the terms “bump” and “rebound”. There are all sorts of shock absorbers built for street-strip and drag race applications. This is a complete set from Strange Engineering. The fronts are single-adjustable while the rears are double-adjustable.