The optimum magnet placement is on a non-drive-side spoke, with the silver side of the magnet pointing towards the tip of the sensor.
You can verify the spoke magnet is placed properly by checking the pattern of the red light blinking.
Point the tip of the speed sensor towards the magnet. You can verify the spoke magnet is placed properly if the red light blinks once per wheel revolution. Note that this is different than the powermeter behaviour.
Normal Halcyon light behaviour.
If you are still having problems after moving the magnet up/down, see below for problems and solutions:
I'm sure I've got it in the right spot, but it still doesn't get picked up every time.
Because the speed sensor works by detecting magnetic fields, and the STAC Zero works by passing your wheel through a very strong magnetic field, occasionally the spoke magnet may not be strong enough to flip your speed sensor. Changing the magnet's polarity can often resolves this problem. See below for how to flip the magnet.
- Carefully take your spoke magnet and allow it to get pulled onto the main magnet arrays of the STAC Zero. Pull the spoke magnet body straight backwards
- this should pull the plastic body of the spoke magnet away from the main magnets, while leaving the smaller magnetic disc behind on the magnet arrays.
- Remove the spoke magnet disc from the main magnet arrays, and place it back in the spoke magnet with the opposite side now facing outwards
The red light doesn't turn on no matter how close the spoke magnet is
See troubleshooting based on light patterns
The Spoke Magnet taps my chain-stays
Some bikes have very skinny chain-stays, and the spoke magnet will tap them as it goes around.
Move the spoke magnet to a spoke on the drive (right) side of the bike, keeping its magnetic side pointed to the non-drive (left) side of the bike. See pictures below. Note that you will want to re-check that your speed sensor can still pick up the magnet after you move it.