Even a good selection of 18's are hard to find these days. Everyone wants 19 or 20.
I would sell the tires if they are nearly new and use the funds toward an 18".
I think the ~20lb Forgestar F14 in 18" are a good value.
This guy scored them for under $1,500 which has to be lowest amount paid for light weight wheel at that size.
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Gloss/Matte Black or Gunmetal Forgestar F14'S? - 6speedonline.com Forums