Mix the brown sugar, paprika, black pepper, salt, garlic salt, cayenne pepper, cumin, onion powder, chili powder, and ground mustard in a large bowl.
Add one tablespoon more of brown sugar for a sweeter rib.
Remove one heaping tablespoon or the spice mix to be used later and set the rest aside.
Trim the membrane from the back of the pork ribs using a sharp knife and a good grip. After a few initial swipes, the membrane should pull off the back with a little tug. Use a paper towel to grip, making it easier to pull.
When the membrane has been removed, cut the racks in half.
Season all sides liberally with the spice mix.
Wrap and refrigerate for 8 to 12 hours before smoking.
When ready to cook, arrange heated coals for indirect heat with a drip pan positioned below where the ribs will be placed.
Allow the grill to preheat to 250 degrees.
Throw a few chunks of lump hardwood over the hot coals to create a delicious smoked flavor and arrange the racks of ribs over the drip pan.
Cover and cook for about 1 hour, keeping an eye on the temperature.
Baste the ribs with a bit of apple cider vinegar.
Cover and cook for another hour to hour and a half.
Continue to keep an eye on the temperature of the grill, adjusting the air vents as needed.
Baste the ribs once or twice more while cooking.
When ribs are close to done, baste the ribs one last time and sprinkle the tablespoon of spice mix you set aside over the meaty side of the ribs to finish the cook.
Pull the ribs off when the meat is fork tender and has pulled back from the bones.