Join Date: Jun 2014
Location: central KY
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Tirerack lists the diameters of all the tires they sell under the spec column in their listings. There won't be a lot of difference in overall diameter in all 3 rim sizes because the aspect ratio (sidewall height) decreases as the rim diameter increases. So, the speedometer won't be affected. What does change, is sidewall width (sidewall to sidewall).
The height of the sidewall will affect handling in curves. The shorter the sidewall, the less the car will lean when you turn, but the taller the sidewall, the more the tire will deflect when you hit a bump. I've driven Impalas with all 3 sizes, and owned an '08 LT with the 17's. I wouldn't recommend the 18's, but the 17's were a good mix of handling & comfort.
Last edited by 1954 Chevy; 07-22-2019 at 06:47 AM.