Smoothly rotate object based on GetAxis

Hello. I was wondering how I could rotate an object (rigidbodied) smoothly based on joystick axis.

using UnityEngine;
using System.Collections;

public class InAirTest : MonoBehaviour {

    //raycasting variables
    public bool offGround = false;

    //rotation variables
    public float speed = 100;

   // public float tiltAngle = 30f;
   // public float smooth = 100f;
  //  float tiltX = Input.GetAxis("Horizontal");
  //  float tiltY = Input.GetAxis("Vertical");
   // public GameObject bike;

    // Update is called once per frame
    void Update () {
        RaycastHit hit;

        Vector3 down = transform.TransformDirection(Vector3.down) * 2f;
        Debug.DrawRay(transform.position, down,;

        /* if (Physics.Raycast(transform.position,(down), out hit))
             distance = hit.distance;
             Debug.Log("Distance: " + distance +;

        //testing if off ground
        //Quaternion target = Quaternion.Euler(tiltX, 0, tiltY);

        if(Physics.Raycast(transform.position, down, out hit))
            if(hit.collider.tag != "ground")
                offGround = true;
            }else if(hit.collider.tag == "ground")
                offGround = false;
                Debug.Log("...on ground......");

        //tell console if off ground
        if(offGround == true)
            if(Input.GetAxis("Horizontal") > 0)
                transform.Rotate(0.0f, Input.GetAxis("Horizontal") * speed, 0.0f);
            if(Input.GetAxis("Horizontal") < 0)
            Debug.Log("in air :D");

This is the code I have so far. It rotates the way I want it to but it is delayed by 1.5 seconds roughly because of the conditional statements I believe also it seems to jump to the next angle. I also dont like how it doesnt gradually progress in velocity of the turn. Any hekp would be appreciated. Thanks.

For those that come across this in the future, I have found a solution using transform.rotate and a vector3. I used the -Input times the bike speed times delta time for smooth rotation.

transform.Rotate(Vector3.right, -Input.GetAxis("RiderLeanfb") * this.bikeSpeed * Time.deltaTime, Space.Self);