Car not rotating when grounded

Hello my car is not rotating while its touching the ground only when its off please help. Heres my code:

using UnityEngine; using System.Collections;

public class BasicCar : MonoBehaviour {

 public string Name = "Car";
 
 public void FixedUpdate(){
     if(Input.GetButton("CarForward")){
         rigidbody.AddForce(Vector3.forward * 20);
     }
     if(Input.GetButton("CarReverse")){
         rigidbody.AddForce(Vector3.back * 20);
     }
     if(Input.GetButton("CarRight")){
          rigidbody.AddRelativeTorque (0, 10, 0);
     }
     if(Input.GetButton("CarLeft")){
          rigidbody.AddRelativeTorque (0, -10, 0);
     }
 }
 

}