Is it a 2 wheel option computer??....if yes- make sure you're computer isn't set for the second wheel. I had the same problem and checked the darn thing over Several times and yes the tire size was right and yes the time was right but the miles and speed were waaaaaaaaaaaay off. When I was checking it Again for the 100,00000,000000 time - I saw this 2 flashing at me and couldn't figure out what it was. After reading the instructions - I realized I had set my computer for a "2nd" wheel optiont that was who Knows what. Once I learned how to make sure the computer was registering wheel #1 (the Right wheel)....all my computer issues vanished!