I think the only thing that effects the "solidness" is the collision box added in the animation browser. If you look at mine and some of the others, you will notice mine comes down to at least halfway into the top of the tires, and some of the other vehicles don't. Other than that, I don't know:/ What makes the Bugger and PosCar so stable; I wish I could figure that one out too Yes!!! Add it to UnWheel