I went for a little cruise on the highway with my Titan and used my GPS to get my speeds. If my GPS is accurate, my speedometer is a fair bit out. For example, when the speedometer says 110 kph, I'm actually doing about 97 kph. 100 kph is actually just under 90 kph. Seems I'm about 10 kph off.
I think what you found there is an industry wide plot to keep people driving at lower speeds. For years now I have noticed that every car I have driven (lots of rentals for business trips) register higher than actual GPS speeds. The cat is now out of the bag!
with the bigger tires on my truck my speedo seems to be right on, well atleast to the speed zone self checker things it dose. (those "speed limit is XX and your speed is XX" with blinky lights)
