I’m apparently on a quest to find ideal neodymium magnets for triggering the cadence side of ANT+ speed/cadence sensors such as the Garmin GSC-10 and Wahoo Cycling Speed/Cadence Sensor. I’d previously tried wide/thin (10mm wide, various thickness) magnets such as the one seen here on the Salsa El Mariachi Ti which sit on the end of the pedal spindle. This works well on the El Mariachi Ti where the crank boot supports it from the side, but on bare cranks it’s not difficult to knock the magnet off. My friend Jeremy has lost at least one magnet this way.
A few days ago I received some 8mm x 10mm (diameter x height) neodymium magnet cylinders via eBay and these seem like an even better solution. On Crank Brothers pedals with 8mm hex sockets in the end of the spindle, these magnets slide snugly into the 8mm hole, with a bit over 2mm poking out. This works great for triggering the reed switch inside the cadence sensor, and unlike other magnets which simply stuck to the end of the spindle, roughly 75% of the magnet is inside of the pedal so it won’t be possible to knock this one off.
Removing the magnet as needed is pretty easy, too. Because there is no flat surface at the bottom of the hex socket the magnet is relatively easy to remove. It can easily be pulled out with another magnet, by sticking a flat piece of steel to the top, or grasped firmly (say, with pliers or some strong finger tips) and slid out. While getting to this fastener outside of a shop isn’t usually needed, it’s good to have the option.