I was setting up two basses at the same time , one needed a tweak one way & one the other , Then I got distracted on the phone , I came back & picked up the wrong bass & turned the truss rode the wrong way I can tighten the rod as much as I like & there is no where as much resistance as there was both ways & the neck doesn't move at all , in fact I can unwind the nut out at least 1cm (access head stock end) . The neck does have carbon rods in it & since changing string to Elixir the action is spot on for me . But I'm aware that I can't change it if needed .