I want to fit new cables to the rear brakes of my 93 Tid (2006 model). I can see how to do it all except that I need to slacken-off the cable adjuster under the centre arm-rest. There's a 13 mm hex screw that does the job. The question is how do I know how far I can unscrew it? If I go too far I'm afraid the screw will come out of whatever is underneath and I'll have to dismantle loads of stuff to get it all back together again. Any suggestions?