Inline editing: browser POSTs not full content

Here is browser script to save "edit_body" field:

<script>
$(document).ready(function(){
 $("#save_editable").click(function(){
  var edit_body = $("#edit_body").html();
  setTimeout(function(){
   $.ajax({
    url:'http://my-url.com/my_editor.php?id_to_update=123',
    type:'POST',
    data:{edit_body:edit_body},
    success:function(data){
     if(data=='1'){
      alert('Saved');
     }
    }
   });
  },5000);
 });
});
</script>

The server do next:

if(@$_POST["edit_body"]){
 $id_to_update=intval($_GET['id_to_update']);
 $edit_body=iconv('UTF-8', 'windows-1251', html_entity_decode($_POST["edit_body"], ENT_QUOTES, "utf-8"));
 if(mysql_query(sprintf('update my_table set body="%s" where id="%s";',$edit_body,$id_to_update)){
  print '1';
 }
}

The problem is:
When "edit_body" contain a lot of text it successfully saves but not full content.
The weaker the browser is, the less text is saved (when more than 20 tabs opened).
In this case I've made setTimeout function with 5 sec delay. But it don't help some times..

How could I tell browser to wait for processing variable "edit_body" before Ajax post..?