[funcars]

There are books that have formulas for calculating sway bar rates based on diameter and shape. Then you can calculate wheel rate based on the combination of the springs, locations, angles and sway bar rates. You can start with wheel rates that have an equal percentage of rate front to rear of what you had before you started changing things and go from there. Some of the Steve Smith books have lots of explanation and formulas to help. They are older books but so are most of the cars we are messing with.

An interesting approach to get a good starting point for your combined wheel rate (vs throwing a dart) is to look at the moment-moment method as explained by the articles at circle track. It is based on using combined wheel rates and calculating the overturning moments at front and rear and attempting to get them approximately equal to get a neutral handling starting point. It is a slightly different approach than looking at roll couple lines and easier to calculate - take a look if you are interested.