Originally Posted by
Seattle Forrest
Most Garmin computers will use a speed sensor if you have one and gps if not. I have a wheel rotation speed sensor, it's useful with a power meter to do aerodynamic testing. Otherwise it isn't worth having.
until you ride into a underground parking lot then its ok if you go less then 6mph. otherwise when you pause and save the rife the GPS starts right back up again. this drove me nuts till I realized what was happening. worth a cheap speed sensor to do away with that.