Wheel Collider Rotation

Hello, I am working on a car game, and have just recently gotten my car to run. However, I'm having issues with the tires rotating. My script is down below. In the last function, Update, I have attempted to make the Front Right tire rotate as the car is moving. It does, but it seemingly rotates to the Z axis as well as the X, so its like a wobbly tire.

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 public class CarControllerV2 : MonoBehaviour {
     
     public WheelCollider FR;
     public WheelCollider FL;
     public WheelCollider BL;
     public WheelCollider BR;
     public Transform frontR;
     public Transform frontL;
     public Transform backR;
     public Transform backL;
 
     private Rigidbody rigid;
     public float maxTorque = 15000f;
 
 
     // Use this for initialization
     void Start () {
         rigid = this.GetComponent<Rigidbody>();
         rigid.centerOfMass = new Vector3(0f,-0.9f,0f);
     }
     
     // Update is called once per frame
     void FixedUpdate () {
         BR.motorTorque = maxTorque * Input.GetAxis ("Vertical");
         BL.motorTorque = maxTorque * Input.GetAxis ("Vertical");
         FL.steerAngle = 200 * Input.GetAxis ("Horizontal");
         FR.steerAngle = 200 * Input.GetAxis ("Horizontal");
     }
 
     void Update(){
         frontR.Rotate (FR.rpm / 60 * 360 * Time.deltaTime, 0, 0);
     }
 }