In Reply to: Mark & Chris - suspension question posted by Mike Zamarocy on August 01, 2000 at 03:32:53:
Too stiff a bar can cause the inside wheel to lift. The energy that would be holding the body in its rolled position against the suspension now goes to the outside tire contact patch. If the tire's got more stick left, it may be no big deal. But usually the tire's unhappy anyway by this point - more force on the contact interface between the rubber and the road will just cause slip. Voila! Understeer!
Also, if the body rolls over, there's more static weight on the outside tires. But if you go stiffer on the bar, the body stays closer to center, so static weight loads the inside tire a bit more. If the roll center is low enough, the positive effect of this might outweigh (sorry!) the negative effect of weight transfer to the outer tire patch - producing LESS understeer. I don't know how to confirm this mathematically, but it makes sense - and might explain the reportedly paradoxical effect of stiffening or loosening the bar from its intermediate setting.