Garmin hub speed sensor aerodynamics

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athletic91
Posts: 299
Joined: Sun Sep 27, 2009 10:03 am

by 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
Posts: 323
Joined: Sun Jan 05, 2014 11:04 pm
Location: Denmark

by Attermann

Just use the gps function

by Weenie


AJS914
Posts: 3129
Joined: Tue Jan 28, 2014 6:52 pm

by 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
Shop Owner
Posts: 908
Joined: Sun Jan 03, 2010 4:58 am

by 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
Posts: 1572
Joined: Tue May 23, 2006 9:39 pm

by 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.
- Parlee Altum + DA9150 + Enve SES 4.5 Ene carbon hubs
- Parlee ESX + DA9150 + THM SRM PM + Enve SES 7.8 carbon hubs
- Moots Vamoots Disc RSL Titanium + DA9170 + Enve 4.5AR CK CL hubs
- Argonaut Spacebike 2.0 + DA9170 + Enve SES 5.6 DT Swiss 240 CL hubs

Swannie
Posts: 278
Joined: Thu Jan 11, 2007 3:48 pm
Location: Belgium
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by 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.

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Calnago
Posts: 7959
Joined: Sun Nov 07, 2010 9:14 pm

by Calnago

Butcher wrote: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.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

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marcelflash
Posts: 117
Joined: Mon Sep 01, 2008 5:07 pm
Location: Zwaag Nederland

by 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.

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573
Posts: 326
Joined: Wed Sep 05, 2012 2:38 pm
Location: West Sussex, UK.

by 573

marcelflash wrote: ↑
Fri Mar 22, 2019 6:31 pm
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
Posts: 864
Joined: Thu Jul 23, 2009 3:35 am
Location: Melbourne, Australia

by robertbb

573 wrote: ↑
Fri Mar 22, 2019 8:00 pm
marcelflash wrote: ↑
Fri Mar 22, 2019 6:31 pm
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
Posts: 327
Joined: Wed Jan 21, 2009 6:58 am
Location: Finland

by kervelo

Attermann wrote: ↑
Fri Mar 22, 2019 4:46 pm
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
Shop Owner
Posts: 908
Joined: Sun Jan 03, 2010 4:58 am

by Butcher

Calnago wrote: ↑
Fri Mar 22, 2019 6:02 pm
Butcher wrote: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.

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Calnago
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Joined: Sun Nov 07, 2010 9:14 pm

by Calnago

kervelo wrote: ↑
Sat Mar 23, 2019 8:50 am
Attermann wrote: ↑
Fri Mar 22, 2019 4:46 pm
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?
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

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Lelandjt
Posts: 509
Joined: Tue Jan 19, 2016 7:10 am

by Lelandjt

kervelo wrote: ↑
Sat Mar 23, 2019 8:50 am
Attermann wrote: ↑
Fri Mar 22, 2019 4:46 pm
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.

by Weenie


kervelo
Posts: 327
Joined: Wed Jan 21, 2009 6:58 am
Location: Finland

by kervelo

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

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