simple constraints set up for tires to the ground
(to remove, if you want to animate the tire flying away, key the constrains off, it’s the setting in the constrain NOT called offset something)
hierarchy
car_group (this is how you animate the position and rotation of the car)
|–carBody_group (this is where you animate the body to give it weight and bounce)
|–tireRF_group
|–tireRR_group
|–tireLR_group
|–tireLF_group
create cubes
make non-renderable and override the shading display so they are just wire… or hide when you are done with the set up.
flatten duplicate and place under each tire
geometry constrain these cubes to the ground
…if you don’t have ground yet leave it until you do or make a test one and delete and remake the constraints when you do.
create a parent constrain, for the cubes under the tires to the car_group
point constrain each tire to their respective cube (those cubes above you just made under each tire)
offset the point constraint so that the tires sit on the ground and are not going through it.
limit the Y trans if each tire_group to the min and mad dis the tire should be from the body of the car.
play with the car and see how it tries to keep it’s tires on the ground. This isn’t the best but for our needs it should be good enough. It would be even better if it had dampening attributes but again we want quick and dirty get this part done, right? we want to get on to FX!
***I didn’t do shocks but if I would, I would parent them to the tires and set driven key them to scale/slide with the Y trans of that tire… Don’t get caught up in that kind of crap, it won’t pay off in the final shot, (well maybe formula one)
I added an atttr to the car_group called tireSpinSpeed and made an expression on all the tires that says
tire.rotateX = time*car_group.tireSpinSpeed;
then you can just key the one attr. again not the best but easier than trying to get the spin to work on the ground
if I come up with something better after more testing I’ll post that. I may still post my mb files. I’ll write to turboSquid and well see. Hey, the rules haven’t even come out yet, I’ve only been messing around so far 
One more tip I’m going to draw a curve on the ground surface and then raise it up a bit and use it as the animation curve, tweak it a bit. then I’ll just animate the rotation and the car body. The point isn’t for most realistice car animation, its all about the crash, I think this will give me a good look in a short amount if time, again so I can get right to the fx.