[Hemipanter]

Hmmm, the torsional stability is a number in Nm per degree of deflection. Just like pound per inch of a spring.

Todays shock absorbers is very sofisticated, and may load the chassies by fare higher force than the springs. If the chassies deflect it will kill the function of the shock absorbers by the same amount as the deflection of the cahassie.
To say anything about the stiffness needed, we must know qoite a bit about the car in question.

From my own experience I can say that 2-3000 fp per degree can not withstand anything more than 1,7 hz of spring stiffness on a 3000 pound car.

Goran Malmberg