I run 205/40/16's and my speedo is not off at all. I drive by one of those road side radars everyday and it's always on par with the speed I'm doing. I say get 45's though because I have ruined one set of rims and gone through three tires hitting no so big pot holes. Anyone have any experience with Hankook tires? My uncle owns a tire shop and says he can get me 205/40/16 ventus for $45.00 a tire his price (he owes me for some computer work).