I just bought a set of 17" Eenkei racing rims with 225/45 ZR Nitto Extreme Performance tires for my '94 Concorde and although i did notice a jump in acceleration (maybe due to the wheels being lighter) i didn't notice a difference in the speedo. Only reason i would recalibrate it is to make sure my govenor isn't cutting in at around 110 instead of 115.