Pour the cola into a large saucepan and let sit until flat. Boil in the saucepan over medium-high heat until it's reduced to 1 1/2 cups (about 45 minutes). Stir in the next 4 ingredients.

Simmer over medium heat until reduced to 2 1/2 cups, stirring occasionally (about 30 minutes). Transfer the glaze to a large bowl (can be made one week ahead; cover and chill. Bring to room temperature before using).

Position racks in top and bottom thirds of oven and preheat to 325 degrees. Sprinkle generously with salt and pepper. Wrap each rack tightly in foil and place on foil-lined baking sheets. Bake for two hours. Cool slightly, snip a small hole in the corner of each packet and pour off the excess fat (can be prepared one day ahead, refrigerated. Let stand at room temperature for one hour before continuing).

Pre-heat the grill. Cut each rib rack into individual sections of three ribs. Remove one cup of glaze and set aside. Add the ribs to the bowl with the glaze and toss to coat. Grill the ribs until brown and glazed, turning continuously, about 5 minutes. Serve, passing the reserved glaze separately.