In a large mixing bowl, combine the sliced cucumbers, grated carrots, and chopped red onion.
In a separate small bowl, whisk together the vinegar, sugar, salt, pepper, sour cream, and mayonnaise until smooth.
Pour the dressing over the vegetables and mix until everything is evenly coated.
Stir in the chopped dill.
Chill the salad in the refrigerator for at least 30 minutes before serving to allow flavors to meld.
Serve cold as a refreshing side dish.