About one hour before smoking, make the dry rub. Combine all ingredients in small bowl; mix well.
Brush thin layer of mustard on both sides of ribs; sprinkle an even coat of dry rub both sides of ribs. Set aside at room temperature for 1 hour.
Heat charcoal or gas grill for indirect cooking at 250 to 300 degrees F. Add drained wood chips, if using.
Place the ribs, meaty side down, over a drip pan and cook for 1 1/2 to 2 hours. Add about 12 coals to a charcoal grill every 45 minutes or so to maintain the heat.
Meanwhile, make the sauce. Combine all ingredients in medium saucepan; bring to a simmer until flavors are blended, stirring frequently. Set aside to cool.
Remove ribs from grill. Double-wrap each rack in heavy-duty aluminum foil. Return wrapped ribs to the grill and cook for 1 1/2 to 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 sauce. Cook for about 5 minutes until the sauce is set. Turn ribs and repeat with more sauce.