On the 55S17W I have drilled a second hole on the brake back plate. This allows me to adjust both sides of the 'automatic' adjuster using a screwdriver. I apply the handbrake by 3 clicks and then adjust the 'automatic' adjuster until all the slack is removed, evenly on the front and back of the adjuster. I find that my 'automatic' adjusters undo on rough tracks or when fording deep water! Also check that the 'H' frame in the handbrake mechanism is not seized as this also seriously reduces the handbrake performance.