Garmin hub speed sensor aerodynamics

[athletic91]

tried google but nothing much came out

imagine spending thousands of dollars on the most aero wheelset only to have the garmin speed sensor wrap around the wheel hub costing a few precious watts...

or am i thinking too much

[Attermann]

Just use the gps function

[AJS914]

You mean the speed sensor that wraps around the hub? I doubt that would make any difference. It's not like you are increasing your frontal area at all.

[Butcher]

I'm no engineer but I suspect it would be close to nothing. The air going thru the spokes would have so much turbulance that it would not cause much drag.

I hate anything hanging on a bike and if I could get rid of any component, I would. That is why I use GPS also.

[kode54]

I use GPS even though its not as accurate. I haven't found a speed sensor that is well designed...most are ugly afterthoughts.

[Swannie]

I read once that it causes drag if its on front hub, therefore best put it on rear hub.
Whith or without is a huge difference in AVG, especially on mtb.

[Calnago]

I'm no engineer but I suspect it would be close to nothing.

What?!! “Close to nothing”, isn’t nothing, and in aero speak that means it counts. Manufacturers are claiming their hubs are more aero etc so strapping a brick onto the center has got to negate whatever aeroness they’ve designed in by oh, about 100%. I kid of course, but you know there’s someone out there saying exactly that.
But it’s ugly af. I much prefer magnet based sensors.

[marcelflash]

I removed the rubber housing and strap. Drilled a hole in the hook of the sensor and used a zip tie. As clean as it gets.

[573]

I removed the rubber housing and strap. Drilled a hole in the hook of the sensor and used a zip tie. As clean as it gets.

Sounds interesting. Any pics?

[robertbb]

I removed the rubber housing and strap. Drilled a hole in the hook of the sensor and used a zip tie. As clean as it gets.

Sounds interesting. Any pics?

+11

[kervelo]

Just use the gps function

I use the hub speed sensor too, because for some reason the Edge 520 GPS is not very accurate. If I compare the distance calculated by the GPS to the distance calculated with hub sensor (having correct wheel size), the difference may be in kms for each training ride.

[Butcher]

I'm no engineer but I suspect it would be close to nothing.

What?!! “Close to nothing”, isn’t nothing, and in aero speak that means it counts. Manufacturers are claiming their hubs are more aero etc so strapping a brick onto the center has got to negate whatever aeroness they’ve designed in by oh, about 100%. I kid of course, but you know there’s someone out there saying exactly that.
But it’s ugly af. I much prefer magnet based sensors.

Which is why you should never take any advice from someone named butcher on the internet.

[Calnago]

Just use the gps function

I use the hub speed sensor too, because for some reason the Edge 520 GPS is not very accurate. If I compare the distance calculated by the GPS to the distance calculated with hub sensor (having correct wheel size), the difference may be in kms for each training ride.

@kervelo: Is your Edge set to "Smart Recording" by chance. If so, try setting it to 1 second recording and see if that improves the accuracy of your distance recorded using GPS only. Still, nothing beat a sensor calibrated to your exact wheel size, unaffected by environmental conditions such as tunnels, tree canopy in wooded areas, etc.

And @Butcher, having a dinner party tonight... T-Bone or Ribeye?

[Lelandjt]

Just use the gps function

I use the hub speed sensor too, because for some reason the Edge 520 GPS is not very accurate. If I compare the distance calculated by the GPS to the distance calculated with hub sensor (having correct wheel size), the difference may be in kms for each training ride.

Is that because the wheel size you entered isn't actually equal to the circumference of your tire? I'd expect a greater error in tire size labeling than GPS tracking.

[kervelo]

@calnago: I use the 1 sec recording.
@lelandjt: I use the measured tire circumference.