Polar S720i and Speed Sensor Issues

Triathlon Forum
1

Here’s my situation. I have the S720i and use it as my cycling computer. Worked perfectly last year until I swapped out my aerobars (Syntace C2 → VisionTech Carbon Pro) at which point I had issues with my speed dropping out. I have “The Nob” (http://www.starbike.com/php/product_info.php?lang=en&table=tblLenker&id=128) that I use to mount my Polar to my aerobars and after pulling out my hair for a while, I remounted my nob such that the screw was on the underside of the mount. Basically I just flipped it upside down, which shouldn’t have made a difference, but it did for whatever reason. I figured the plastic screw was somehow interfering with the signal… whatever.

I start riding outside again this year and my first couple of rides goes ok. Then a few weeks later… same issue. My speed starts dropping out, but I didn’t change anything this time. I thought it might be the battery, but it works with the watch even farther away from the sensor but not if it’s on the mount itself. So I flip my Nob mount BACK TO THE WAY IT WAY ORIGINALLY and it magically works again. I’m stumped.

I doubt it’s the speed sensor itself. The battery was just changed last fall and if I remove the watch from the mount, but keep it in range the speed picks up. Also, if I tilt the computer so it’s angled forward, it’ll eventually pick up too. So I’m assuming it’s something screwed up with the mount itself. At this point I’m wondering if the antenna in the speed sensor or the watch is getting jarred around and causing weird issues. I have no idea?

Any other S720i users ever have this problem or anything like it? What do you all use for your aerobar mount? I was thinking about swapping out my aerobar mount entirely, but don’t want to replace it with something else that isn’t going to work either. Thoughts?

2

I’m having the same problem right now. I don’t have “The Nob”, but I have something similar. When the watch is perfectly level it is erratic in picking up speed, but when I angle the watch downwards about 10 degrees it works fine. When I just had it mounted sideways on the aerobars I never had a problem. For some reason I think those solid “nobs” somehow interfere with the transmission from the speed sensor. Seems to work fine when worn on the wrist for racing though.

3

Have you increased the speed sensor strength? There is a way to change the signal strength by changing the settings in the sensor. Do a google search and you should find the details.

4

Yup. I get the same thing. If I tilt it forward, it works but is hard to see. When it is level, I got no love. I don’t know what mounting thing you have, but if you can, you might try flipping it upside down and see if that helps?

5

Haven’t done that yet. I don’t think it’s a power issue since I can take the watch off the mount and it still registers speed even farther away from the sensor? But maybe switching the jumper around would increase the signal just enough to get through the plastic on the nob thing. It’s worth a shot, I guess.