WordPress: have a nav menu full width

I use wordpress 3.9.1 and i would like to have a navigation menu full width.
The theme i use is Maya with a fixed layout and there are these rules regarding the css

#nav {
margin: 30px 0 20px 0;
border-top: 1px solid #CFCFCF;
border-bottom: 1px solid #CFCFCF;
text-align: center;
}

#nav ul {
list-style: none;
margin: 0px;
font-size: 12px;
}

Now, i’ve transformed into:

#nav {
margin: 30px 0 20px 0;
border-top: 1px solid #CFCFCF;
border-bottom: 1px solid #CFCFCF;
text-align: center;
    position:absolute; left:0;right:0;
 }

#nav ul {
list-style: none;
font-size: 12px;
    position:relative;
    margin:0 auto; width:100%; max-width: 2000px;
   }

but it does not work, remains inside its fixed container.

How can I do?

edit:
header.php

<!-- START NAV -->
                <div id="nav" class="group">
                    <?php  
                        $nav_args = array(
                            'theme_location' => 'nav',
                            'container' => 'none',
                            'menu_class' => 'level-1',
                            'depth' => apply_filters( 'yiw_main_menu_depth', 5),   
                            //'fallback_fb' => false,
                            //'walker' => new description_walker()
                        );

                        wp_nav_menu( $nav_args ); 
                    ?>    
                </div>
                <!-- END NAV -->