Soak 1 cup hickory chips in water for 15 minutes.
Using a paring knife, trim membrane off bone-side of racks. Place on a baking sheet.
In a bowl, thoroughly combine rub ingredients. Remove 2 tablespoons and set aside for sauce making. Pat ribs dry and sprinkle remaining spice rub over both sides of both racks.
Set barbecue grill for indirect heat. Place hickory chips in a disposable aluminum pie plate directly over heat source. Place a second, large aluminum roasting pan to one side of the heat source, and add 2 cups water. Arrange cooking grates over pans. If using gas, turn on burner under wood chips to high, and other burners to medium. Close lid and preheat 15 minutes.
Reduce main burner to medium and turn other burners off. Place ribs over pan of water, bone side up. Cook 90 minutes, turning once halfway through.
Place a rack over a baking sheet. Pour enough water in bottom to just cover. Transfer ribs to rack and wrap tightly in foil. Place pan in preheated 250°F oven for another 1½-2 hours. Transfer to cutting board, tent with foil and rest 10 minutes.
Combine ketchup, molasses, vinegar, water, liquid smoke, and reserved spice rub. Whisk thoroughly. Mop ribs thoroughly with sauce, using about 1 cup of sauce. Serve remaining sauce on the side.