Well, I think I am going to have to agree with the post I linked earlier. I did a short 60 mile test of the odometer and speedometer verse the GPS. On average the speedometer read 3-5 MPH higher than the GPS speed, however, the odometer only varied from the GPS on the two occations in which I traveled through the tunnels and lost GPS signal. And then it was only by .1 mile each time. Once I cleared the tunnel, the difference remained the same once again and the odometer continued to track exactly with GPS. This leads me to believe the post that the sensor that feeds into the computer is the same, but the processing for speed and miles is different. I know in the past with cable driven speedometers it was a direct correlation between miles and speed, but I think in the computer age things have changed. I plan to test it further this weekend on a longer run.
Well after a 550 mile trip to OH, the odometer was only 1 mile off from GPS while the speedo was almost 5% off the entire way. I guess they aren't linked directly after all.
