I had previously used a GPS to mark where 5, 15, 25, ... 75 mph were on the speedometer with little stickers. When I hit top speed with mine, the needle was where I estimated the 85 mph mark would have been. On mine, the speeds indicated on the speedometer are much higher than what I am really going. When I am going 75 mph on a GPS, the speedometer says something a little over 80.
Scott