Place ribs on a rack in a shallow roasting pan. Scatter 4 cloves of sliced garlic over ribs. Cover, and bake at 300°F for 3.5 hours. Cool slightly.
In a small bowl, mix together white sugar, paprika, salt, black pepper, chili powder, and ground cumin. Rub spices over cooled ribs. Cover and refrigerate overnight.
Next day, in a small saucepan, mix together brown sugar, cider vinegar, molasses, ketchup and chili sauce, Worcestershire sauce, lemon juice, onion, dry mustard and 1 clove of crushed garlic. Simmer over medium low heat, uncovered for 1 hour. Reserve a small amount for basting and use the remainder for a dipping sauce.
Preheat grill for medium heat.
Place ribs on grill. Grill, covered for about 12 minutes, basting with the reserved sauce until nicely browned and glazed. Serve with remaining sauce for dipping.