WheelControls.cs

using UnityEngine;
using System.Collections;

public class WheelControls : MonoBehaviour {

    public float maxSpeed;
    public float acceleration;
    public float rotationAcceleration;

    private float horizontalVelocity;
    private Rigidbody2D thisRigidBody;
    private float direction;
    private GameObject rengas;

    void Start () {
        thisRigidBody = this.GetComponent<Rigidbody2D> ();
    }

    void Update () {
        direction = Input.GetAxis ("Horizontal");
        horizontalVelocity = System.Math.Abs (thisRigidBody.velocity.x);

        //kaksi tapaa kiihdyttää: AddForce ja AddTorque
        if (horizontalVelocity < maxSpeed) {
                // thisRigidBody.AddForce (new Vector2(direction, 0) * acceleration);
                thisRigidBody.AddTorque (-direction * rotationAcceleration);
            }

    }
}