If you change the rolling circumference of your wheels and tires, the speedometer no longer reads correctly, and your odometer will also gradually become inaccurate. Assume for example that you bought a car brand new and changed the wheels and tires on day one from 185/65/14 to 205/50/15, that makes your speedometer over read. Consequently, the registered odometer reading will also differ. So for example, when you get to 10,000km of driving (in the real world), your odometer will actually read more. It won't be a huge difference but it is one of the reasons why most car dealers have a disclaimer on their secondhand vehicles telling you that they won't guarantee the displayed mileage.
It's worth pointing out that without exception, all motorbike speedometers are designed to inflate the ego of the rider by at least 5%. In some cases, they are are much as 10% optimistic. ie. the speedometer on a motorbike will always over-read. 100mph? Not likely - you're actually doing closer to 90mph.
+1
My ego deserves a little inflation
