I finally found out why when I am going 65 according to my speedometer, which is the speed limit, everyone is flying by me... I have undersized tires!
This is really pissing me off. I took my GPS around town this evening and when my speedo reports 40 MPH I am really going 36 MPH. I did not have a chance to get up to 65 but I bet that speed is really fast compared to what I am traveling.
I am supposed to be running 235/75 R17s and I have 245/65 R17s. According to the conversion done on some other web page, the stock size is 30.9 inches, and the size I am running is 29.8. A full inch smaller.
Will undersized tires cause any adverse effects on my Truck? They don't have much tread left on them so by next spring I'll be getting new ones anyway, for now I need to figure out at what speeds I am going on the dash to what they really are on the street.