Quote:

You have to take into account the material's modulus of rigidity.



No, not unless one bar is aluminum and the other is steel.

For stiffness of a spring or sway bar, steel is steel. All steels have the same elastic modulus (which defines stiffness), regardless of alloying, heat treatment, density, time of the month, etc. Strength depends drastically on those details, but not stiffness. And since a sway bar is a device that is created with stiffness, not strength, as the design parameter, steel is steel.

-Kurt 50% of all people are below average.