Car Wheels sink through the ground

Hello,

I have imported the cataluna car from the car tutorial into my game. The problem is the tires fall through the ground and the car rests on the underbelly. I tried adding mesh colliders to the wheel which works, but when i get in it to drive my modified settings to the car cause the car to bounce in tiny but uncontrollable ways and the car is useless. I was looking for a way to simply disable the colliders through script when the player is in the car. Any Suggestions? This is the code i have for getting in and out of the vehicle.

var car : Transform;

var player : Transform;

var exitPoint : Transform;

var doorTriggerLeft : Transform;

var PlayerCamera : Camera;

var CarCamera : Camera;

var isPlayerVisible : boolean;

function Update(){

if (Input.GetButtonUp("Enter Vehicle")&& isPlayerVisible){

    // make player invisible and still standing

    player.gameObject.SetActiveRecursively(false);

    player.gameObject.active = false;

    // parent player to Exit Point

    player.parent = exitPoint.transform;

    player.transform.localPosition = Vector3(-1.5,0,0);

    // parent PlayerParent to car

    exitPoint.parent = car.transform;

    exitPoint.transform.localPosition = Vector3(-0.01,1,0);

    // Enable Car as controllabe object

    GameObject.Find("Car").GetComponent("Car").enabled=true;

    ChangeCarCamera();

    }

    else

    {

if (Input.GetKeyUp("r")){

    // make character visible again

    player.gameObject.SetActiveRecursively(true);

    player.gameObject.active = true;

    // unparent player from everything

    player.transform.parent = null;

    // parent Exit Point to door Trigger

    exitPoint.parent = doorTriggerLeft.transform;

    // disable car as controllable

    GameObject.Find("Car").GetComponent("Car").enabled=false;

    ChangePlayerCamera();

    }   

}

}

function OnTriggerEnter(Player : Collider) {

isPlayerVisible = true;

}

function OnTriggerExit(Player : Collider) {

isPlayerVisible  = false;

}

function ChangeCarCamera() {

PlayerCamera.enabled = false;

CarCamera.enabled = true;

PlayerCamera.GetComponent("Audio Listener").enabled = false;

CarCamera.GetComponent("Audio Listener").enabled = true;

}

function ChangePlayerCamera() {

PlayerCamera.enabled = true;

CarCamera.enabled = false;

PlayerCamera.GetComponent("Audio Listener").enabled = true;

CarCamera.GetComponent("Audio Listener").enabled = false;

}

Try adding wheel colliders to them