Did this just start or was the problem there since the alignment? Could be a bent wheel, broken tire belt, rust or scale stuck between the wheel and brake rotor or between the rotor and hub. Alignment could have been set wrong. Check the tire wear patterns. Do you feel a "feather-edge" or is there more wear on one side of the tread on one or both tires? Is the steering wheel straight when driving straight ahead? Does the car pull to one side when you let go of the steering wheel?