The sway bar mounting will have an adjustment to allow more or less preload on the bar. By preloading the sway bar, static weight can be changed. This will affect crossweight. This is just one of the ways that the sway bar can be used as a tuning tool.
Sometimes the sway bar is set to be loose when the car is rolling straight. In this case, the car can bounce up and down under the control of its spring rates but with the bar having no effect. However, when the car enters a turn and the chassis begins to roll to the right, the sway bar will begin to exert its force.
There are several sizes and types of sway bars. Most OE and many racing sway bars are one piece. They are bent to fit within the confines of the chassis. On some aftermarket chassis, like those used with Modifieds and Late Models, a multipiece sway bar is used. In these, the bar is straight with splines on each end. Arms with matching splines are attached to each end. This three-piece setup simplifies changing the bar.
All sway bars have a spring rate. Since this is a tuning tool, it is often changed for different track conditions. The working length of the bar is the distance between its mounting points on the chassis. While this is not absolutely true, it can generally be used as the comparison rate between bars.
A difference of only a few thousandths of an inch in the diameter can make a significant difference in its spring rate. Remember, the sway bar is a torsion bar, which is a spring. As such, it will have a spring rate. The working length of the bar and the diameter are the factors that determine its spring rate.
A bar with a small diameter and a high preload may look the same on wheel scales as a stiffer spring with no preload on the bar, but it won't necessarily act the same on the track. It might be preferable to use a stiffer sway bar with no preload. A spring change would then be necessary to bring the crossweight back. Another situation that can arise in the Street Stock classes (where only OE springs or same-height springs are allowed) is the stock sway bar may be used to adjust crossweight. If the link connecting the left end of the sway bar to the left-side suspension is tightened down (shortened), then more crossweight will be added. An adjustable link here can make this adjustment easy.
The next question: How much force do we want? The simple answer is . . . the right amount! Unfortunately, this answer is not found in a book in exact numbers. There are a number of ways to look for the answer. Driver feedback, observation of the car during cornering, the careful use of a tire temp gauge, and learning to use wheel scales are some of the ways. Through all this you must remember that a fast race car is the best combination of all the factors in the car. The sway bar is just one of these tools.
This might be considered a...
This might be considered a normal position for an OE sway bar. The car is level and at rest. The tube in the middle covers where the bar is cut in half. This model allows the twist of the bar to be shown.
OE sway bar shapes may be...
OE sway bar shapes may be something like this. They must be bent to clear the OE chassis and its stock parts. More bends lessen the spring rate.
Aftermarket style sway ba...
Aftermarket style sway bar.