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You need to provide more dimensions to get a solid answer. The question is the rim, not the tire. To see if a rim will hold a tire, mechanics at the shop are the place I'd go. I run the HD Stinger rims on my 2009 Fatboy, which are 18" rims. Rear looks to be 18x7 running 200mm, and front is 18x4.5 (measuring bead to bead) running 130mm.
So will it work? Doesn't sound like it will. At least not without spacers. Your tires sound awful skinny for those nice wide tires that she came with.
After doing a Google and EBay search, I can give you the definite possibility of a firm maybe. Found some in the sizes you're looking at and the only thing that comes to mind are axle diameters and maybe spacers. A 200mm tire on a 5.5 wide rim is a stretch to my thinking. 4.5 might be a better fit. Hopefully someone with more knowledge will chime in. Good luck!
I've been looking for a solid chrome rim to match the J.J. Doom rim I have on the front of my '07 NT. Several shops, to include Heartland, recommended the 18x5.5" rim. I think you'll be good to go.
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