Just in case anyone is doing research on weighted tags....
I was transporting a busted Sentra to the scrap metal yard so I got to drive over the scales going in and out (payment is based on the difference) and discovered that my F250 diesel quad cab + steel deck trailer + Sentra + plus a little household junk came to almost 12K pounds. I figure that would rack up quite the penalty for my 4000 Lb rated tag (that rating was done by the DMV based on the previous owner's declaration). I "suspected" that I was probably risking a fine but hadn't realized just how high that could be.
Sheet 148 of the DMV downloadable PDF file (referenced later) indicates that a vehicle licensed for non-commercial use can have a combined weight (vehicle + trailer + all contents) of 9,000 or less. Above that weight you are basically a commercial vehicle. Pages 138, 148, and 151 are key places to start reading. Page 151 has the rates for various weight limits. There is a big jump from 12,000 to 14,000 Lbs.
NC Title Manual, 14th Edition. Revised August 2011
http://www.ncdot.gov/download/dmv/NCTitleManual.pdfAt only 335 pages this is a great evening read
Charlie G