Combine the brown sugar, salt, pepper, allspice and thyme leaves in a small bowl. Rub both sides of pork chops with herb mixture. Let stand 15 to 30 minutes. Discard any remaining herb mixture.
Prepare a medium-hot fire in grill. Pat pork chops dry while being careful not to remove the rub. Grill chops, over direct heat, turning once, to medium rare doneness about 4-5 minutes per side or until the internal temperature reaches 145 degrees Fahrenheit, followed by a 3-minute rest time.
