Pull off the thin membrane from the underside of the rack of ribs. Blot each rack of ribs with a paper towel to dry. Massage the spice rub into the ribs on all sides. Allow ribs to stand at room temperature for up to 1 hour before grilling.
Prepare grill for indirect heat. Layer soaked wood chips and charcoal. When the coals are ashed over, spread them out in one area of the grill so the ribs can cook over indirect heat (not directly over the coals). Cover the grill and bring it to between 225°F and 235°F.
Cook ribs bone side down, with the grill lid closed, 3 1/2 to 4 1/2 hours, or until the meat just starts to shrink back from the ends of the bones. To ensure even cooking, place an oven thermometer next to the ribs.
To finish, baste ribs on both sides with Stubb's Bar-B-Q Sauce, and place them back on the grill for 5 to 10 minutes. Once completed, set the rib racks on a baking sheet and cover with foil; let rest 10 to 20 minutes; then slice and serve.