# Garmin 800 and GSC10 Question?



## nevermiss (Feb 12, 2011)

I have a Garmin 800 that I move between my road bike and mountain bike. I have the cadence sensor on my road bike and I've added one to my mountain bike.

My Question: When you add the GSC10 to the Garmin 800, do you get any additional data other than cadence? The speed and distance are still calculated by the GPS I would presume.

I did input my tire circumference, but I imagine the wheel sensor would only be applicable to sensors that receive input from the GSC10 that do not have GPS capability and this input would be used for speed/distance calculation.

Interestingly, I have an old computer with wheel sensor(no cadence sensor) on my mtn bike and the speed indicated on the Garmin 800 seemed to be lower compared to my old computer with wheel sensor-especially at slower speeds.


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## drmayer (Apr 19, 2007)

the GSC10 senses both speed and cadence. If paired with a Garmin head unit, the Garmin will use the speed data from the sensor instead of GPS. The wheel speed sensor signal is less likely to be lost in dense trees/urban areas where a GPS signal might be lost. If you set the wheel size to "auto", the unit will calibrate itself my comparing GPS speed to wheel speed for a few mins at the start of the ride.


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## nevermiss (Feb 12, 2011)

drmayer said:


> the GSC10 senses both speed and cadence. If paired with a Garmin head unit, the Garmin will use the speed data from the sensor instead of GPS. The wheel speed sensor signal is less likely to be lost in dense trees/urban areas where a GPS signal might be lost. If you set the wheel size to "auto", the unit will calibrate itself my comparing GPS speed to wheel speed for a few mins at the start of the ride.


Thanks for the info! I was hoping that it would get the speed data from the sensor since it seems to be more accurate. Now I also know how the "auto" calculation is done. I just did a roleout of my circumference and converted to mm and input it manually.

I tried to search the garmin site as well the garmin forums find my answer without any luck so I thought I would post here since there seems to be some good people with a wealth of garmin knowledge!

Thanks again!


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## gmngueko (Mar 14, 2004)

*speed of GSC10 only if GPS off*

I strongly think "drmayer" is wrong :nono:, all the Garmin gps will always use the speed(distance) coming from the GPS excpet if the GPS is turned off or no GPS reception possible.
So for speed and distance the GSC10 is a fallback from GPS !
obviously the cadence is alway coming from the GSC10


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## Harold (Dec 23, 2003)

gmngueko said:


> I strongly think "drmayer" is wrong :nono:, all the Garmin gps will always use the speed(distance) coming from the GPS excpet if the GPS is turned off or no GPS reception possible.
> So for speed and distance the GSC10 is a fallback from GPS !
> obviously the cadence is alway coming from the GSC10


You are incorrect. Details about the use of the GSC10 data are model-specific.

For the older models, you may be correct. However, for the 500 at minimum, and probably the 800 also, you are incorrect. These newer models handle the GSC10 differently.


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## gmngueko (Mar 14, 2004)

*my bad I was partially wrong*

indeed "Natehawk" is rigth for older Garmin unit 305 at least, the GSC10 was a fall back for the GPS when gps was off or no reception (under a tunnel).

Now I re-read the manual for the edge 500 and edge 800 and it is indeed the other way around. GPS is used for speed and distance only if there is no GSC10 (speed and cadence sensor).
This is actually a very good news for me :thumbsup: , I always thought it should have been that way since for me the sensor is more accurate for instant speed and for the distance (if calibrated properly), especially instantaneous speed which is always wrong via GPS.

So I have less reason not to upgrade to a edge 800 or 500, 
perfect thanks "Natehawk".


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## slocaus (Jul 21, 2005)

nevermiss said:


> Thanks for the info! I was hoping that it would get the speed data from the sensor since it seems to be more accurate. Now I also know how the "auto" calculation is done. I just did a roleout of my circumference and converted to mm and input it manually.


Consensus on the Garmin forums is that introduces error. Let the GPS autocalulate wheel size and it does it at the start of each ride and gives more accurate results. It also accounts for tire wear and inflation pressure.


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## c0nsumer (Mar 17, 2008)

You all may be interested in this research that I did this past weekend regarding the Edge 500 with and without a GSC 10. In short, I feel the GSC 10 is required for accurately logging a trail ride. I was able to induce under recording of 1/3 in a worst-case test while using only GPS. For GPS+Sensor it was spot-on.


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## Harold (Dec 23, 2003)

c0nsumer said:


> You all may be interested in this research that I did this past weekend regarding the Edge 500 with and without a GSC 10. In short, I feel the GSC 10 is required for accurately logging a trail ride. I was able to induce under recording of 1/3 in a worst-case test while using only GPS. For GPS+Sensor it was spot-on.


Albeit an exceptionally detailed and well-documented example, this has been known for awhile. I wouldn't exactly call it research, either, since it only accounts for a single receiver (there is no documentation of variation between receivers, which I am absolutely certain exists) or variation by any other sources.

Still, it does help explain the benefits of frequent sampling and some issues with the Edge 500.


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## c0nsumer (Mar 17, 2008)

NateHawk said:


> Albeit an exceptionally detailed and well-documented example, this has been known for awhile. I wouldn't exactly call it research, either, since it only accounts for a single receiver (there is no documentation of variation between receivers, which I am absolutely certain exists) or variation by any other sources.
> 
> Still, it does help explain the benefits of frequent sampling and some issues with the Edge 500.


Would you happen to know of any other writeups (or posts or whatnot) that you could point me to that come to the same conclusion? While I suspected (and was told by numerous people) that using the GSC 10 "helps" or "makes things more accurate" I didn't really have much to go on besides hearsay.


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## Harold (Dec 23, 2003)

c0nsumer said:


> Would you happen to know of any other writeups (or posts or whatnot) that you could point me to that come to the same conclusion? While I suspected (and was told by numerous people) that using the GSC 10 "helps" or "makes things more accurate" I didn't really have much to go on besides hearsay.


I don't specifically follow the Edge 500 threads in here, but I do read them for informative purposes, but it's been mentioned many times that folks get better results with the speed/cadence sensor. I am not sure if you'd call those accounts hearsay or not, but I read enough of them that I've been holding it as truth for some time now. And FWIW, the Edge 800 also handles the speed/cad sensor the same as the Edge 500 as I hear it, which seems to be a better way than the Edge 305 and the 705.


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## c0nsumer (Mar 17, 2008)

NateHawk said:


> I don't specifically follow the Edge 500 threads in here, but I do read them for informative purposes, but it's been mentioned many times that folks get better results with the speed/cadence sensor. I am not sure if you'd call those accounts hearsay or not, but I read enough of them that I've been holding it as truth for some time now. And FWIW, the Edge 800 also handles the speed/cad sensor the same as the Edge 500 as I hear it, which seems to be a better way than the Edge 305 and the 705.


Yeah, I'd pretty well accepted the "better" idea, but it really had me wondering just how much better. What I found was that it's so much better that I'd personally consider the Edge 500 unusable for trail riding without the wheel sensor.

I like to see such things quantified. 

(Sounds like the Edge 800 is a winner as well... It's just overkill for my needs so I'll stick with the 500.)


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## slocaus (Jul 21, 2005)

c0nsumer said:


> What I found was that it's so much better that I'd personally consider the Edge 500 unusable for trail riding without the wheel sensor.


I've posted the press releases and all the information I can find from Garmin.. 
http://forums.mtbr.com/7658826-post7.html
http://forums.mtbr.com/7857353-post16.html

They are all about the design, riders, and introduction event were all road races or racers. No where do they explicitly mention mountain bikes, though as one person pointed out, they do not exclude mountain bikes either.

If you do a browser search on the page, you will find:

The Garmin Edge 500 page DOES NOT mention mountain biking.
The Garmin Edge 800 page DOES mention mountain biking.

It all comes down to Buyer Beware and Shop Wisely. If you fail that, then blame Garmin for misleading you and ruining your life, like a few continually remind us with posts here.


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## Bicyclelist (Sep 5, 2006)

I was about to ask the same question as the OP, thanks for all the info!


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## crank1979 (Feb 3, 2006)

I have an Edge 705 and just yesterday bought an Edge 800 to go with my new road bike. My plan is to use the 800 on the roadies and the 705 on the mtbs. 

Connecting the 800 on the new bike was no problems. It detected the cadence/speed sensor without any problems. When I tried to use it on the old bike it didn't pick up the older cadence/speed sensor. Any ideas on what I need to do so the 800 will work with both sensors on different bikes?


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## slocaus (Jul 21, 2005)

[email protected] said:


> I have an Edge 705 and just yesterday bought an Edge 800 to go with my new road bike. My plan is to use the 800 on the roadies and the 705 on the mtbs.
> 
> Connecting the 800 on the new bike was no problems. It detected the cadence/speed sensor without any problems. When I tried to use it on the old bike it didn't pick up the older cadence/speed sensor. Any ideas on what I need to do so the 800 will work with both sensors on different bikes?


You need separate profiles for each bike, then pari each sensor to each profile and it should work fine.


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## crank1979 (Feb 3, 2006)

Thanks. Done and each has a different sensor id. I'll double check tonight to make sure it worked.


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## wickedfn4u (Jan 4, 2008)

If it picked up speed from the sensor first, why does this keep auto pausing in the woods and right back to resume when I am moving. I have checked in the garage on my stand and the speed works when I spin the wheel. It picks up the speed and cadence when I test it. Guesses?


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## Eckstream1 (Jul 27, 2011)

I just picked up an 800...
The GSC 10 does not play well with my FS Santa Cruz... I can't align the sensor for both speed and cadence.

I see an older sensor mentioned... What model number is that? Also anyone using the older sensor with a FS with an elevated chainstay?


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## c0nsumer (Mar 17, 2008)

wickedfn4u said:


> If it picked up speed from the sensor first, why does this keep auto pausing in the woods and right back to resume when I am moving. I have checked in the garage on my stand and the speed works when I spin the wheel. It picks up the speed and cadence when I test it. Guesses?


I strongly suspect that auto-pause is done by GPS, even if speed comes from the speed sensor.

I'd love to see Garmin's Edge x00 code.


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## wickedfn4u (Jan 4, 2008)

That is silly, why have a sensor then?


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## Harold (Dec 23, 2003)

Eckstream1 said:


> I just picked up an 800...
> The GSC 10 does not play well with my FS Santa Cruz... I can't align the sensor for both speed and cadence.
> 
> I see an older sensor mentioned... What model number is that? Also anyone using the older sensor with a FS with an elevated chainstay?


You do not need to use Garmin's sensor exclusively. There might be other sensors on the market that will work for you. Just as long as the sensor is ANT+, you're good.


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## slocaus (Jul 21, 2005)

NateHawk said:


> You do not need to use Garmin's sensor exclusively. There might be other sensors on the market that will work for you. Just as long as the sensor is ANT+, you're good.


Ok, here it is for the 101st time! 

Ant+ Compatibility Chart


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## Eckstream1 (Jul 27, 2011)

NateHawk said:


> You do not need to use Garmin's sensor exclusively. There might be other sensors on the market that will work for you. Just as long as the sensor is ANT+, you're good.


Yeah I just ordered the Wahoo Fitness Speed/Cadence Sensor... Considering just running the speed sensor though.



slocaus said:


> Ok, here it is for the 101st time!
> 
> Ant+ Compatibility Chart


Thanks for the link! It's nice to know what works and what doesn't!


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## Harold (Dec 23, 2003)

slocaus said:


> Ok, here it is for the 101st time!
> 
> Ant+ Compatibility Chart


thanks for that. I knew that site existed, but did not have the link available for pasting.


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