This is weird. I have computers on both front and rear wheels. Front was there first, added rear for stationary trainer use. Took bike on road for twenty miles. Computers are off by .4 miles. Rear one measures MORE distance. Rear one is cheap Schwinn, but wheel circumference input is measured in mm, so input was accurate to 1 mm. Cateye on front has input only for 700cx28. Even though cateye was way more expensive, could it be possible it is less accurate than the cheapy Schwinn?