Last issue we took a look at adjustable shock absorbers in general and Strange Engineering’s billet bolt-in shocks in particular. To recap some of that article, 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. As pointed out in the last section of this chapter, with today’s shocks, you are given the opportunity to control the wheel motion. In turn, you 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? A shock is a hydraulic device that resists chassis movement by passing 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.
Front Strange Engineering single adjustable shocks are set here at the adjuster. Turn the adjuster fully counterclockwise. That’s the beginning of adjustment or full soft. From this point, you can establish the baseline for your car. See the text for initial settings based upon application (street or strip).
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. Forces push the racecar up and forward -- and 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 create traction to start this movement. Too much body separation can lead to some undesirable side effects: 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 is similar to wheel hop and can be addressed similarly. For the most part, a "bald" starting line will mandate a softer rebound setting to apply the tires with more force. A good starting line can use a stiffer setting. A stiffer 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 housings moving up or into the chassis. The bump adjustment is critical 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, try using a slightly stiffer compression setting.
So Far So Good…
Where do you 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.
Many adjustable drag race shocks are similar when it comes to adjustment. The shock absorber doesn't have to be removed for adjustment. Once it's installed in the car, all changes are handled externally by way of the adjustment knob. After installation, the knob is accessible through the side of the spring (typical front applications).
Using our Strange Engineering shocks as the example, setup works like this: Turn the knob fully counterclockwise. The "end" of the adjustment (where it will not turn and click any further) is the softest setting, and it position “1”. By turning the knob clockwise, each click will increase the shock resistance. The full stop counterclockwise (front shock baseline) has valving that's similar to a 90/10. As you can see, this offers a very large range of adjustment. On the single adjustable models, once you go past 6 clicks clockwise, the adjuster works primarily on extension (rebound). Moving all the way to the right (clockwise) will make the shock stiff.
According to Strange, the starting point for adjustment on a single adjustable front shock is as follows:
* Turn to position 2 or 3 (position “1” is full counterclockwise)
* To increase weight transfer (front end travel) rotate counterclockwise)
* Turn to position 4 or 5 (position “1” is full counterclockwise)
* For firmer ride, rotate clockwise