Prepare the grill for indirect cooking over low heat (250° to 300°F).
In a small bowl mix the rub ingredients.
Remove the membrane from the back of each rack of ribs. Season the ribs all over with the rub, putting more of it on the meaty sides than the bone sides. Arrange the ribs in a rib rack, all facing the same direction. Allow the ribs to stand at room temperature for about 30 minutes before grilling. Meanwhile, make the glaze.
In a small saucepan over medium heat, mix the glaze ingredients.
Brush the cooking grates clean. Place the ribs over indirect low heat, as far from the heat as possible, with the bone sides facing toward the heat. Close the lid. After 3 hours, check to see if any rack is ready to come off the grill. They are done when the meat has shrunk back from most of the bones by ½ inch or more. When you lift a rack by picking up one end with tongs, the rack should bend in the middle and the meat should tear easily. If the meat does not tear easily, continue cooking for up to 4 hours.
Remove the ribs from the rib rack and transfer to a sheet pan. Lightly brush the ribs on both sides with the glaze. Lay the ribs flat on the cooking grate, with one rack at a time over direct heat. Grill them, with the lid closed as much as possible, until the ribs are a little crispy on the surface, 10 to 15 minutes, brushing them, turning them, and swapping their positions occasionally. Return the ribs to the sheet pan, give them one last coating of glaze, and cover with foil to keep warm for as long as 15 minutes. Cut the racks between the bones and serve right away.