Quote:

I am starting to wonder if Sway bar Diameter has that much of a direct/precise input on handling, since there is so little empirical data advertised anyway.



No, it doesn't. On any kind of race/high-performance car, sway bars are used to dial in oversteer, or understeer. That's why race cars use adjustable sway bars.

Spring rates are far more important to handling than sway bars, and a sway bar that's too big can easily negatively effect handling. A sway bar basically links the two sides of the front suspension together. When one tire moves up, the sway bar pulls the opposite tire up with it. This gives the appearance of a flatter cornering car, but think about what's happening to the inside tire as it gets lifted up. It loses grip because the sway bar is trying to pull the tire up, taking weight off that corner. Sure, a flatter cornering car seems like a good idea, but if a sway bar is used as a bandaid for too-soft springs and the flat cornering comes at a cost to cornering grip, what's the point?

Basically, a sway bar is a small part of the suspension that should be used as a tuning device, not a cure all. A good handling car will have a well matched suspension, and I'd bet most people would be surprised how soft the sway bars are on real race cars.