You know, the odometer sensor is connected at the transmssion after the gears. It is designed to count the rotations of the shaft which drives the wheel and translates to the distance traveled. The reading takes into account the original size of the wheel (circumference). So, if you put a smaller wheel, the odometer indicates more than you really traveled (But you increased the torque at the wheels). Conversely, a bigger wheel results to under-registration.