Sonata I45 (YF - 2011+) :: 2013 - Rear Humming Or Roaring Noise

My 2013 Sonata GLS has a noise that is in the rear of the vehicle going down the road. I rotated tires from back to front and noise seemed to move to front. I moved them back to rear so noise would be behind me. This told me the noise must be the tires or wheels. The tires are a long way from being worn out so I keep running them. I have the stock alloy wheels but previous owner put 225/40R18 tires on car. Tires size on door jam label says tire size on this GLS is supposed to be 225/45R18.

Could it be the wheels and not the tires? Another possibility could be factory lug nuts on back wheels. I read in my street rod magazine that lug taper length must be shorter than the taper length on wheel lug holes. Lugs cannot be so long that lugs hit the wheel backplate leaving the wheels slightly loose and not centered leaving a slight tire wobble when driving. The article says the lug taper much be shorter than the taper in the wheels in order to snug the nuts. I did not switch the lugs when rotating tires to front. If this is the problem rather than tires or wheels, Hyundai had a lug supplier problem.