transform.rotation doesn't stop

What i want in this script i made is that my object which is a tire, needs to rotate the to side when pressing "a". When it then hits 16 if(transform.rotation.z > 16)
Then it stops. transform.rotation.z = 16; But somehow it continues to rotate and doesn't stop at 16. If you have any questions, ill answer them.

 #pragma strict
 
 var speed : float;
 var turnSpeed = 0.0;
 var turnMotion = 0;
 function Start () {
 
 }
 
 function Update () {
 speed = gameObject.Find("Rubber").GetComponent(Movement).speed;
 transform.Rotate(Vector3(turnSpeed,0,0) * Time.deltaTime);
 turnSpeed = speed * 20;
 
 if(transform.rotation.z > 16) {
  
          transform.rotation.z = 16; }
          
 
 
 if(Input.GetKey("a"))  {
 transform.Rotate(Vector3(0,0,turnMotion) * Time.deltaTime);
      
          
         
     }
 }