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Seen other threads on this, but none with my specific questions.

My '13 R/T Classic came with 245/45R20 on 8" ENVY Wheels.

I'm considering a wheel size change to 18 (maybe going with steel police wheels, or some other retro look I can get in 18s but not in 20s.)

Stock 18's on the '13 R/T were 235/55. My handy-dandy tire size calculator says that this swap would create 1.8% speedo error and would lower my car by 6.4mm. I'm not liking this. If anything, I'd like more ground clearance.

However, if I were to go with 245/55R18, the speedo error is only 0.25% and car is only 0.9mm lower. This would seem to be so close to the 245/45R20 that no speedo calibration would be needed. However, I didn't gain any ground clearance (something I could use on the crappy roads around where I live).

So I plugged in 255/55R18 and get a 1.25% speedo error (less than stock 235/55R18's) and increased ground clearance by 4.6mm. This would give me wider tire than my stock 20's and more ground clearance and they'd certainly still fit in the wheel-wells.

So, given that the stock 235/55R18's for this car are the greatest deviation from the stock 20's, does anybody see any issues with going with either 245/55R18 or 255/55R18 on this car?

And other than the speedo calibration (how is that accomplished anyway?) would the <2% deviation in tire diameter throw off any of the other calculations the CPU might use for God-knows-what?
 

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Currently running 295/45R18 and 255/45R18 Nitto 555G2’s . You might not be able to go that wide on police wheels (not sure what width they are) but my OD is close to stock where my speedo hasn’t really been affected.

I highly recommend going to 18’s if you can get it done right.
 
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