Sounds to me like the rotor is not running true to the pads and the pads are set too far from the rotor so they don't scrape. Therefore you have to pull in more cable to get complete contact. Or your cable is tired out ?
I have Avid BB 7's and you leave the caliper loose to the frame mounts, then adjust each pad hard to the rotor before tightening the caliper to the frame. When the rotor has almost no runout relitive to the pads, they can be kept very close to the rotor surface. Read your manual and go through the adjustment procedure.
Hope thats not too long.
:-)