also,

http://www.coniserver.net/wiki/index.php/Car_Physics_with_many_cars

this will get you more than one car, and this is
for Lite-C, but I think you should do what xbox said,
and use this (his seems a little easier, but doesn't seem to
have tires, there is 3 things wrong that I had to do with
the one I started with)....

to disable the tires/chassis,

in your case:

phent_enable(car, 0);
move car
phent_enable(car, 1);

my case:

phent_enable(PlCar01_wheelFL,0);
phent_enable(PlCar01_wheelFR,0);
phent_enable(PlCar01_wheelRR,0);
phent_enable(PlCar01_wheelRL,0);
phent_enable(PlCar01_chassis,0);
then move the car/wheels, then
phent_enable(PlCar01_wheelFL,1);
phent_enable(PlCar01_wheelFR,1);
phent_enable(PlCar01_wheelRR,1);
phent_enable(PlCar01_wheelRL,1);
phent_enable(PlCar01_chassis,1);



also, look at the gamestudio manual,
to change the friction, you would

phent_setfriction(car, 50);

or

phent_setfriction(car, 20);

you can change them mid-game when you
go over different surfaces...

-Jimc74