No significant impact according to my westcoast DCX tech rep. I'm currently running the Goodyear 'Eagle F1 Supercar' tires; P245/45ZR20 up front & P255/45ZR20 on the rear. :cool2:larrynipon said:If I move from the stock 18" / 60 profile Conti's, to 20" / 45 profiles, any idea if there will be a significant impact on speedo accuracy? Also, how wide can I go? Any suggestions for the best tire/wheel setup on a 20" wheel?