Today I went out and braved the cold for about 15 minutes. I wanted to check my speedo so I took the GPS with me. Seems that the speeo is somewhere between 8
and 10 mph off. Any ideas what might be causing this? At 55 my speedo is reading about 63-65. My first thought was that the gears in the wheel hub might be
fucked up, but it doesn't jerk around, seems smoth just reads slow. I am running a stock wheel tire combo.

