I am ready to put on new tires (06 prius). I Want Goodyear TT's. What is the difference between the tires mentioned above? Why do most posts recommend the 60's over the 65's? The 65's are taller........but wouldn't they actually give me less rotations per mile thereby cheating my odometer just a smidge? With the 60's I believe I would be cheated in the odometer just a bit, if i understand the sizes correctly.
There is a change in the aspect ratio, so there would be an effect on MPG. However, this change may be in the same error range as the MPG calculations of the Prius. Note that the rolling resistance may be different and this may have a bigger effect on the MPG then expected, so get a good MPG baseline before the change. The tire you are selecting is a very long lasting tire if I understand right (Assurance TripleTred-Wear 740?). I think this is a good decision. Let us know how it turns out.
185/65R15 = 24.5" Outside Diameter Integrity OEM tire = 76.969" circumference = 823.188 rev/mile 195/65R15 = 25.0" Outside Diameter Assurance Triple Tread = 78.540" C = 806.725 rev/mile 195/60R15 = 24.2" Outside Diameter Assurance Triple Tread = 76.027" C = 833.393 rev/mile (OD figures from Goodyear web site, C and rev/mile calculated, actual rev/mile different) So the 195/65 will make your speedo and nav 2% fast (823.188/806.725) and the 195/60 will be 2% slow (823.188/833.393).
