They adjust how much weight transfers to the rear skid when on the throttle and how soon the suspension couples over bumps. The larger the gap, the more weight you transfer, the longer it takes to couple(the height of your top shim also has something to do with it all)... the more weight you transfer, the lighter the steering gets (ski's come off ground higher). Usually you want a bigger gap in powder and a tighter gap for trail riding and drag racing. The more weight you transfer, the more energy you waste in a drag race. Its a bunch of physics crap.