Remove the thin white skin from the back of each rack of ribs.
Mix all other ingredients (spices, sugar, salt and pepper) in a bowl and use two-thirds of mixture to coat all ribs on both sides. Place on roasting pan and cover in the fridge for 4 to 8 hours. Save the remaining one-third of spice-mixture for later application.
Get grill up to 325 degrees F then place ribs on grill over indirect heat. Grill for about 1.5 hours (back back ribs) or 2 hours (spare ribs or St. Louis-cut ribs). When finished, ribs should have slight bend when lifted and bones should start protruding from ends. Fifteen minutes before cooking time is complete, season ribs with remaining spice-mixture.