About 30 minutes before smoking, make the dry rub. Combine all rub ingredients in a coffee grinder; grind until smooth. Generously coat both sides of ribs with rub. Set aside at room temperature for 30 minutes.
Heat charcoal or gas grill for indirect cooking at 275 degrees F. 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.