A roll bar should be used as a tuning device rather than an initial design item. This means that it should be used to obtain the optimal handling given certain circumstances, only after the rest of the suspension (in this instance especially the spring rates) were optimised. Typically, sway bars are used as tuning devices when one use a single suspension set up (same dampers and spring rates) for all tracks, and then use the roll bars to tune the suspension. However, I believe one should first adjust the dampers before you adjust the sway bar.
Typical Situation where above applies, would be when you will race on a bumpy track. First soften the damping, and then fine tune with sway bars. The sway bars will mainly assist with balancing of the car front to rear but on a bumpy track will often be contra productive, as it will unload a wheel where you do not want it to. But generally it should provide more good than bad, as you should simply reduce sway bar leverage on a bumpy track. In saying this, it probably is clear that I believe adding a non adjustable sway bar, is no good at all. It should be adjustable for height (used when doing corner weights) and should be adjustable to provide more or less leverage to increase or decrease load.
Now having said that, it may appear that I am saying one must add sway bars all round, which is not always true. I have seen GT cars without sway bars front or rear, and although I do not understand it, reckon those guys must know what they are doing. I pressume it is because the setup is already perfect and they are able to adjust damping and spring rates to the optimum. The Ultima also has no sway bars, and upon discussing it with them, Ultima reckons it is not required due to the stiffness of the suspension. It makes sense to a certain degree. A sway bar is used to assist with weight transfer management (especially roll of the vehicle) and if the spring rates are very hard, there should be minimal roll already.
If you use the car for gymkhana or autocross, I presume you may want a softer suspension if compared to track racing. You especially want the rear to provide best traction, which could mean that you need the front sway, but the rear is less important (general rule is stiffer front sway provides better traction on the rear, and vice versa). The front sway can then be used to provide more (increase the sway leverage) or less (decrease leverage) traction at the back and could in that way assist with overall balance.
Be it as it may, a sway bar is sometimes used as crutch to correct other issues with the suspension, and one should not fall into this trap. It could be that a car with no sway bar works better than one with two, as the rest of the setup is already very good. You will however then loose this as tuning device given different circumstances.
Another reason why you may find a car to handle better without sway bar, is that the sway bar is installed incorrectly. When doing wheel corner balancing, the sway bar must be disconnected at one side, and then be connected without causing load on either side at standard ride height. A sway bar may be connected causing load to one side, which will make handling unpredictable and the car may feel that it handles better without, but for the wrong reason.
In my view, adding a sway bar correctly, should assist under most conditions. I would propose that a sway bar is added at least at the non-drive end (with the spyder will be front end with drive at the back). But the sway bar should be the last adjustment being made to tune the suspension. A lot of guys reckon that adding a stiffer sway bar always makes the car handle better - I disagree. It depends on the rest of the suspension set up.
Apologies for the long post!
