Drum brake pad to drum distance?

Adjustment is not causing them to lock up, unless they are way WAY too tight to start with. One "popular" cause is hydraulic......the master cylinder rod or something else is keeping the master from returning the piston, and keeps the ports in the bore covered. To find out quickly, with the brakes in the "locked" problem area, crack a tube fitting and see if there is pressure, then see if the wheels turn