Mix the rub ingredients. Using a blunt knife, slide the tip under the membrane in the middle of the back of each rack of ribs. Lift and pull off each membrane. Season the racks evenly with the rub, putting more of the rub on the meaty side. Allow the racks to stand at room temperature while you get the smoker ready.
Prepare the smoker for indirect cooking with very low heat (130 – 150°C/250 – 300°F), filling the water pan half to three-quarters with water.
Add the wood chunks to the charcoal and close the lid. When smoke appears, place the racks, bone side down, over indirect very low heat. Put the lid on the smoker, and then close the top vent about halfway. Cook the racks for 2 1/2 hours, maintaining the temperature of the smoker between 130 and 150°C (250 and 300°F). Meanwhile, make the glaze and sauce.
In a saucepan, mix the glaze ingredients. Bring to a simmer over a medium heat and cook for 3–5 minutes, stirring occasionally. Remove from the heat.
In another saucepan, combine the peanut butter, 125 ml (4 fl oz) of the apple juice and the vinegar. Heat slowly for about 2 minutes over a medium heat until the sauce is smooth, whisking constantly. Remove from the heat.
After 2 1/2 hours, lightly brush the racks on both sides with the glaze. Continue to cook for 30 minutes more.
After 3 hours total cooking time, the meat will have shrunk back from most of the bones by 5 mm (1/4 inch) or more. If it has not, continue cooking until it does. They are done when you lift a rack at one end with tongs, bone side up, and the rack bends so much in the middle that the meat tears easily. If the meat does not tear easily, continue to cook until it does. Another way to test for doneness is to push two adjacent rib bones in opposite directions. When the racks are fully cooked, the meat between the bones should tear easily (but should not be mushy either).
Return the saucepan with the peanut sauce to a medium heat. Add 60–125 ml (2–4 fl oz) of the remaining apple juice and warm for a few minutes, stirring occasionally. Lightly brush the racks with more glaze, and then cut the racks into individual ribs. Serve warm with the peanut sauce.