About 1 hour before smoking, make the dry rub. Combine all rub ingredients in small bowl; mix well. Generously coat both sides of ribs with rub. Set aside at room temperature for 1 hour.
Heat charcoal or gas grill for indirect cooking at 275oF. Add drained wood chips, if using.
Place the ribs, meaty side up, over a drip pan and cook for 2 hours. Add about 12 coals to a charcoal grill every 45 minutes or so to maintain the heat.
Remove ribs from grill. Double-wrap each rack in heavy-duty aluminum foil. Return wrapped ribs to the grill and cook for 2 hours more over indirect heat, until very tender. Add more coals as needed to maintain temperature for a charcoal grill.
Remove ribs from grill and unwrap. Place ribs over direct heat on grill and brush with barbecue sauce. Cook for about 5 minutes until the sauce is set. Turn ribs and repeat with more sauce.
Serve ribs with remaining barbecue sauce.