I know I can fit 255/45/R18 and 245/55/R18 on my 06 Charger RT without any undesirable consequences. I assume I could also fit 235/50/r18 on there as well. They are not as wide as either tire and not taller than the 245/55/R18. Is my logic correct?

 

245/55R18 works with no problem. 255/45R18 would fit but is so much shorter in height that it would show much more fender well gap and throw the speedo off.