@EdMercer: The center of mass is always centered. You can change the inertia matrix by choosing a different object type in ph_setmass, but that is only relevant in low-g situations. As fogman suggested, the easiest way to lower the center of gravity is changing the weight ratio of body and wheels. With wheels weighing 4 times as much as the body you can get good results. The other option is a passable&invisible weight entity added to the car via a (fixed) slider.