It is your lucky day, Tiberius!
Here are the the old calculations I did for the Capri.
IMHO it is important to get the roll angles right (based on photographs)
Then when you know the range of the wheel rates (depends if it road car or race car) or when you know the actual springrates and the suspension geometry, you can calculate te remaining 'springrate' of the rollbar.
In these RACER wasn't able to cope with camber changes so suspension geometry effects in the handling were limited. Besides most of the handling is determined by the inertia, wheel rates and damper rates in my view.
For a live axle, there actual two wheel rates: one in roll and one in bumps (driving in a straight line). So a other method is to use the wheelrates for the straight line situation and use the ARB-rates to get the wheel rate in roll situation.
But I haven't played Racer for more the two years so things might changed:tongue: