I got the wireless wheel speed sensor with my Garmin, for more accurate distance and speed measurements. The transmitter also measures cadence. I used to occasionally time my cadence by counting for 15 or 20 seconds, and thought that was all I needed.

But, I actually look at the cadence numbers all the time. It's surprising to me how far off my guess of cadence can be. I want to be in the low 90s, but I'll look down and see low 80s instead. Or if I'm trying to put out a big effort, I try to keep it up near 100.

So I really find it useful to have an accurate cadence display all the time.


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I think all wireless transmitters go into a very low power mode when the wheel is stopped, and only send the radio signal when they see the wheel is turning. My Garmin rear wheel transmitter is still on it's original CR2032 coin battery, after more than a year.

Auto On usually refers to the timer stopping when you aren't moving. There's two reasons for this: 1. You don't have to remember to hit the start button (Garmins don't have an auto start, and I do forget to start it sometimes.) 2. Your average speed isn't reduced by the elapsed time you aren't moving.