Calibrate your speedo?
 

when i drive past the local this is how fast your going signs it says 40 and my speedo says 47. that seems like enough to make my odometer tick a lot fast then i should. is there a way to recalibrate it or a place i could take it to and have it fixed? i know tire size will make it change but my 15x50s are about the same as the stock 16x45s.

How accurate is the radar box? It could be off and your car could be fine.

there are 6 in the hood and they all say about the same and i can reset the trip at a mile marker and the next 20 (that's as high as i have counted) don't go past me anywhere near a full mile according to the trip