[Racecomp Engineering]

Second, a quote from a discussion I had with Bryan at JRZ USA a while ago:

Originally Posted by Bryan at JRZUSA

Old theories and descriptions of the roll center show that the RC should never pass through the ground. Thats incorrect. Using force based roll centers or what I call, Newtonian physics, the RC passing through the ground doesn't have the "over center" effects of the RC going very far out sideways. It't not necessarily a bad thing, I'd focus more on the mechanical balance of the car and the cambers than exactly where the RC is relative to the ground.

One reason someone would put the RC close to the CG is to reduce the roll moment carried by the springs. The roll moment not carried by the springs is then carried by the suspension links as manifested by the "jacking force." Note that there is no significant reduction in "weight transfer" by raising the RC. You are only balancing between which part the load transfers over. The only major determining factors for load transfer are the CG height and track width. Since the suspension arms are much stiffer than the spring/damper, the response of the car is altered as well. This can manifest in a quicker roll response at the chassis, or degraded dynamic grip since the vertical load might build up faster than the cornering load can. High RCs can also mean more track change with suspension movement and more tire scrub. Again, the scrub affects the response of the tire. There is a limit to effective roll center height.

Note that changing the RC height changes the camber curve as does the caster. All of these effects are interdependent which is what makes K&C machines popular. In my opinion, its more valuable than time at a shaker rig given that you don't have the kinematic data from the car.

- Andy