Advices about handling?

Hi guys, I modified the mass of the Infernus to 999999 and the speed same as mass.
Well, it looks like the car upper side touches the wheels and Niko doesn't open the door just does an animation and gets in and if I increase it too much the car just disappears when I want to get in. Anyway, do you know what number should I put to get maximum strength crashing whatever but that it doesn't make the car look like it's touching the ground??