icctrombone, You can remove the magnet and see if it sticks to something iron, most likely it will. Most problems are due to the gap between the sensor and the magnet and the relationship of the two pieces as they pass each other (magnet may need to be moved up or down slightly). I just fixed a problem with my wireless' sensor moving because I waxed the forks prior to it's installation. It'd read 2 MPH-34 MPH within just a couple of pedal strokes.

Brad