Rear drum brake has clunk noise and vibration

I'm not sure if the tire I replaced would have caused my problem, but it's ironic that after 2 days of driving with a mismatched tire on the rear passenger side of my car the second day I suddenly felt this vibration in my steering wheel and then heard a clunk clunk, clunk, clunk, noise that is in sync if you will (revolutions?) By the speed of my tire moving while accelerating! I can literally move my drum with my fingers but it's not affecting my emergency brake when I do a hill stop. What made it come loose and how do I fix that? Will it go away if I put the right size tire back on it?