Light a grill or heat oven to 300° F.
In a small bowl, combine the sugar, chili powder, salt, mustard powder, and thyme. Rub the mixture on the ribs, coating each side.
If grilling, cook the ribs bone-side down over medium-low heat or when the coals are well covered with ash. Adjust the flame or add coals as necessary. Cook for 1 1/2 hours. If oven roasting, place the meat in roasting pans bone-side down and cook for 1 1/2 hours. The ribs are done when you can insert a fork between two ribs and separate them.