Wheel Magnet on Hub

I found a good way to get the wheel magnet mounted so that it is out of the air stream and has reduced rotational mass.

The speed sensor (for Ergomo) was just long enough that I could tuck it inside of the chain stay keeping it out of the main air flow. Then simply glue the magnet on to the hub body

This works well on a disc wheel as well.

Magnets are available at reasonable cost (30-50 for $8.95, depending on what size you want, plus shipping):

www.rare-earth-magnets.com