I noticed something interesting with my trip ODO reading. My daily commute, when I don't deviate one little bit from my standard route read 10.9 km, with the stock Potenzas (195/55R15) inflated to 33 psi, 11.0 if there is a fair bit of wheelspin.

With my snows - Kumho KW-11's (185/65R14), inflated to 31 psi, I get a reading of 11.1 km. In theory, I should be getting a lower reading with the Kumhos, given their theoretically bigger diameter (and supposedly identical diameter according to both Bridgestone's and Kumho's websites).

Am I missing something, or could the actual tire sizes be that much off in manufacturing? Not that it really matters for such a small difference.