Combine the contents of 3 tea bags with 1/4 cup brown sugar, 2 teaspoons salt, 1/4 teaspoons pepper and the zest of one orange in a bowl. Rub the tea mixture over both sides of the ribs, which have been pat dry and from which you've removed the tough membrane from the underside. Place the ribs in a roasting pan, meat-side up, and bring to room temperature, about 20 minutes.
Preheat the oven to 275°F Steep the remaining 3 tea bags in 2 cups of boiling water which have been poured into a cup, about 5 minutes. Discard the bags and stir in the remaining 2 tablespoons brown sugar and the juice of half the orange. Pour the mixture around the ribs in the pan. Cover tightly with foil and roast in the center of the oven until tender, about 90 minutes.
Meanwhile, put the potatoes in a pot of salted water; bring to a simmer and cook until tender, about 10 minutes. Do not overcook. Drain and lay out on a cookie sheet to cool slightly. Mix the mayonnaise and parsley in a large bowl. Grate in the zest of half the lemon, and the juice of the lemon half. Fold in the potatoes and add 1 1/2 teaspoons salt, and pepper to taste; refrigerate until ready to serve.
Remove the ribs from the oven and increase the temperature to 450°F Pour the cooking liquid into a saucepan and bring to a simmer over medium-high heat. Baste the ribs with some of the liquid, then return to the oven and cook uncovered, basting a few times, until the ribs are dark and glazed, 20 to 30 minutes.
When the remaining liquid in the saucepan is syrupy, add lemon juice to taste. Brush the ribs with the glaze. Glaze will thicken as it cools. Cut the racks into pieces and serve with the potato salad.