Center of Gravity (CG) is defined as that point about which, if the body were suspended from it, all parts of the body would have equilibrium ..i.e.. without tendency to rotate. it is the 3D balance point of the race car. all acceleration forces acting on a body can be considered to act through the CG of that body..we have the cg to be as low as we can get it.
Mass Centroid- is related to Cg ..sort of...ifin we slice the car into a series of sections, like a loaf of bread, each slice would have its own CG...if, in a side view, we draw a line connecting each sliced CG..we have the Mass Centroid Axis..not really a straight line but close to it.
it gives an indication of the distribution of the vehicles mass in the vertical plane.
Roll Center of the suspension is that point , in the traverse plane of the axles, about which sprung mass of that tend of the vehicle will roll under influence of centrifugal force. It is determined by drawing a line from the tire contact patch to a point in space that is the intersection of the upper and lower suspension arm linkage angles.
The CG and RC are located at different points. Usully the CG is many inches above the RC. CG can be change by moving " weight " around on the chassis.. The RC is changed by modifying how the upper and lower control arms mount to the chassis. Correct changes will improve the weight transfer to the rear tires thus improving traction.
lot of other stuff goin on here.. race car math of some is on my post in General Physics post " Race Car Physics" 31 Dec 2008