The 15" rim and tires I have are 2% taller than stock. The winter tires have a taller sidewall, 205/70R15. So it does affect the speedo, but just a bit.I assume this impacts your speedometer and odometer calibration. With smaller rims, you're likely to be really going slower than your reported speed, and really putting on fewer miles/kms than your reported distance. That's standard with any car when you change the tire size. But with the Niro being so heavily computerized (and so heavily goal oriented toward fuel economy), I wonder if it might have any impact on any of the computer's decision making logic? I imagine that there's a way to recalibrate the speed/distance logic so that it reads correctly with the smaller rims, but I'm not aware of what that entails.