If you wish to remove the default wp menu in the admin bar of WordPress 3.3+, include the following snippet in the file: function.php

function cj_admin_bar() {
 global $wp_admin_bar;
add_action( 'wp_before_admin_bar_render', 'cj_admin_bar' );


To remove the admin bar completely from the backend and optimize performance, install this wordpress plugin:

CJ Remove WP Toolbar