The magnet is attached to the wheel itself and the sensor to the fork so that the magnet can pass it when the wheel turns and give a reading. We recommend that the magnet goes near the center of a spoke, between the hub and rim. Usually, this is on the front wheel, but there are some rear-wheel devices. However, for all devices, positioning should be checked carefully as the sensor will have a maximum distance it can be from the device, wired or wireless. Check that the bike speedometer is picking up the movement before you fix anything in place more tightly by turning the wheel a few times.