baustin wrote:The size of the tires on the vehicle can affect this. I have not checked my Leaf to see if it is correct, but I see this on my truck. I installed tires that are one size larger than the truck was shipped with. When the speedometer shows 65mph, the GPS display shows I am going 68mph.
If the Leafs are all calibrated for the largest size tire option available for the car, but it ships with a smaller size, I believe that would result in the discrepancy being reported.
The tire size between the OEM 16" and OEM17" is good for 2.x/3.x% depending on which way you do the math (815/837 vs 837/815). The rest is based on that stupid law that says that the car has to be sold with a speedometer that reads 0% to +10% on speed. There is a fine for the manufacturer if the speed is under reported but not if over reported less than 10%. So they make sure it will over report on even the largest tire that will fit.
Then you the consumer can remove the OEM tires and put on tires that correct that error and you as a consumer are allowed to adjust any calibration setting the speedometer might have.