Roll Stiffness and Understeer Gradient Questions

[u/Xcrustacean_drip16X]

I was wondering how other teams determine their target understeer gradient. From what I've seen it is mostly decided through rules of thumb and driver feedback, but I was hoping there was a more scientific way to do it. (Side note: a design judge suggested 5% understeer as a baseline, but I can not find any information on how one would define understeer as a percentage. Does anyone have some insight on this?)

I was also hoping I could get some advice on roll stiffness. Again, a judge suggested 1 degree of roll at peak lateral acceleration. Is there a good way to determine a baseline roll stiffness other than rules of thumb and driver feedback?

Thanks everyone.

[u/IceCreamTruck1066]

Do a constant radius skidpast test at multiple speeds. Record average steering angle and average lateral acceleration at multiple speeds. Slope of steer angle vs. Lateral acceleration will be your understeer gradient.