Garmin speed/cadence sensor issues
 

I did my club's monthly TT on saturday, and I found quite an interesting problem with my sensor. First, I will note that I did not end up going with GPS (buyers remorse now) and that i am using the speed cadence sensor with one of garmin's running watches as my main bike computer. So the circuit is 18.7 miles, what do i get? 19.3 miles...

Why? Well, when i was descending down one of the long straight hills, i noticed my cadence go up above 105-110, and suddenly the speed said that I was going 60 mph, not kph. then when i stopped pedaling, it flipped back to around 37 mph. I am guessing this means the watch thinks my pedaling is just my wheel spinning when i am at high cadences.

Does anyone else have this problem? Is there any way to fix it? Is there a problem with my sensor?

Thanks.

Which garmin unit are you using?

if you get the crank magnet near the unit and don't pedal it will whack the readings. It'll kill the battery that way too if the bike is parked.

FR60
I am really talking about pedaling at cadence of 100+ not stopped, when stopped it always shows 0 cadence, and a reasonable speed.

I have found Garmin customer service to be second to none. Give them a call and I am sure they will answer your questions.
Good luck and happy ridding.

CCrew - Nice insight! I've occasionally seen cadence readings of 140+ from my Garmin 500 with speed / cadence sensor when I upload my rides to Garmin Connect. After reading your post, I realize that I might be "parking" the crank magnet next to the chainstay mounted speed / cadence sensor on long, fast descents. Hmm, I'll watch for it and report back. Anyone else care to jump in?!