E1Allen
Youngster
Ok, so that is my stupid little graph that didnt turn out very well to attempt to show a difference in the speedo and GPS MPH differences. My GPS does not register in decimals once over 100mph and I obviously can't go the exact speed, but I got pretty close. I don't think this is accurate 100% but there is an obvious difference. I did this all using my deserted stretch of highway.
Speedometer GPS Difference
70 68.3 1.7
100 96.8 3.2
120 116 4.0
140 134 6.0
154 147 7.0 <--- Didn't feel like going any faster today.
160 152 8.0 <--- That's a guess. 163 is the fastest i've gone.
165 154 9.0 <--- My guess is she isn't going much faster than this unless you have a nice big downhill.
Anyways, all I wanted to do was to try and have some kind of reference between GPS and what the Speedometer says. This is with 3700mi on stock tires. I don't know if that will make much of a difference but thats that. .02 from me.