Garmin Reading Low

Arbuckle23
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Garmin Reading Low

Postby Arbuckle23 » Wed Aug 09, 2017 7:19 pm

My rides are suddenly getting shorter and my speed slower.
I use a Garmin 520 and use a GC10 for speed cadence.
I thought the battery must be getting low, so fitted a new battery and repaired.
Still reading low.
If I watch the 520, the speed reads low, then jumps up to where it should be.
I have checked the magnet position to make sure in range and aligned properly, all seems good.
Anyone have any clues?

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rodneycc
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Re: Garmin Reading Low

Postby rodneycc » Wed Aug 09, 2017 7:28 pm

Are you sure its just not winter affecting your stats? I find it affects me about 4 or 5km/h when I'm suited up like the Michelin Man.
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march83
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Re: Garmin Reading Low

Postby march83 » Wed Aug 09, 2017 7:37 pm

yeah, I'm noticeably slower in the winter. Commuter shorts, backpack, warm jacket, long sleeves, it all adds up.

Arbuckle23
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Re: Garmin Reading Low

Postby Arbuckle23 » Wed Aug 09, 2017 7:37 pm

Nah. My regular lap is a distance I know well and coming up varying shorter distances at the moment. 22 km instead of 25 km tonight.
And when heading downwind the speed would fluctuate between 22 - 35 km/h and I hadn't changed my speed at all.
Slogging back into the wind I was slow, but not that slow :)

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ValleyForge
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Re: Garmin Reading Low

Postby ValleyForge » Wed Aug 09, 2017 7:57 pm

Having had a wide range of Garmins over the years, and being the family Garmin fixer, I have seen occasional software updates reset the wheel circumference. Might be worth re-checking.

Next might be worth checking your numbers using GPS only (unpairing the GSC would be the easiest way). The speed will wobble all over the place but should average out "correctly".

Or ride with a friend with a Garmin & compare.
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rodneycc
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Re: Garmin Reading Low

Postby rodneycc » Wed Aug 09, 2017 9:57 pm

Just remember to back the Garmin up before doing any updates. The amount of times I have lost settings after an update, its not worth the grief. The backup copy has saved me more than a few times!
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hamishm
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Re: Garmin Reading Low

Postby hamishm » Wed Aug 09, 2017 10:11 pm

Could be a faulty GSC-10. Try riding without it (ie, unpair it) and see how you fare.

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bychosis
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Re: Garmin Reading Low

Postby bychosis » Thu Aug 10, 2017 7:37 am

I unpaired my GAC10 after it started dropping out and showing zero as a speed while I was definitely moving. It would stop and start fluctuating between zero and my current speed. I thought it was the battery, but changing it (admittedly with an old battery that may have also been flat) didn't help. I ditched it and didn't have troubles after that apart from the occasional GPS glitch under heavy tree cover etc. previously if ditched the HRM for similar reasons, I kept flatlining.
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MichaelB
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Re: Garmin Reading Low

Postby MichaelB » Thu Aug 10, 2017 7:58 am

I'm like bychosis - headunit only. Makes life simpler

Arbuckle23
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Re: Garmin Reading Low

Postby Arbuckle23 » Thu Aug 10, 2017 8:09 pm

Well, went out tonight without the GC10 and we are back at the correct distance, with nice stable speed instead of all over the place, using the GPS on the 520. Looks like a dodgy GC10

My only issue with continuing with just the GPS is that I like to monitor my cadence to ensure I don't get lazy and slack off :)
I may have to buy a cadence sensor, Garmin or Wahoo?

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bychosis
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Re: Garmin Reading Low

Postby bychosis » Thu Aug 10, 2017 9:08 pm

Go old school. Every now and then watch the seconds tick by, count how many pedal strokes in 15secs, then quadruple.
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Arbuckle23
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Re: Garmin Reading Low

Postby Arbuckle23 » Thu Aug 10, 2017 9:30 pm

bychosis wrote:Go old school. Every now and then watch the seconds tick by, count how many pedal strokes in 15secs, then quadruple.


You are assuming that mental arithmetic (now that's a term that shows my age) and I get on together :wink:

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bychosis
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Re: Garmin Reading Low

Postby bychosis » Thu Aug 10, 2017 10:11 pm

Arbuckle23 wrote:
bychosis wrote:Go old school. Every now and then watch the seconds tick by, count how many pedal strokes in 15secs, then quadruple.


You are assuming that mental arithmetic (now that's a term that shows my age) and I get on together :wink:

Count for 60 secs then :mrgreen:
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MichaelB
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Re: Garmin Reading Low

Postby MichaelB » Fri Aug 11, 2017 8:59 am

Arbuckle23 wrote: My only issue with continuing with just the GPS is that I like to monitor my cadence to ensure I don't get lazy and slack off :)
I may have to buy a cadence sensor, Garmin or Wahoo?


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ValleyForge
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Re: Garmin Reading Low

Postby ValleyForge » Fri Aug 11, 2017 9:24 am

The first thing to usually go in the GSC10 is the magnetic reed switch in the wheel sensor. The models over the last few years have omitted some foam packing in the tip which I think leaves the reed more vulnerable should it get hit repeatedly by the wheel magnet.

The cadence sensor is much better protected so I have had a few where it still worked. Maybe yours too?
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vosadrian
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Re: Garmin Reading Low

Postby vosadrian » Fri Aug 11, 2017 10:37 am

Just remove the wheel magnet and continue to use the GC10 for cadence. I have had a faulty GC10s in the apst do the same thing and just stopped using them for wheel speed and all good for cadence. The Garmin will use the GPS for speed if it detects no speed signal on the GC10.
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Kev365428
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Re: Garmin Reading Low

Postby Kev365428 » Thu Aug 31, 2017 12:32 pm

Arbuckle23 wrote:Well, went out tonight without the GC10 and we are back at the correct distance, with nice stable speed instead of all over the place, using the GPS on the 520. Looks like a dodgy GC10

My only issue with continuing with just the GPS is that I like to monitor my cadence to ensure I don't get lazy and slack off :)
I may have to buy a cadence sensor, Garmin or Wahoo?


Just take the magnet off the spoke - no more speed sensor, but the cadence sensor will still be ok.

Kev.

mikgit
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Re: Garmin Reading Low

Postby mikgit » Thu Aug 31, 2017 10:57 pm

vosadrian wrote:Just remove the wheel magnet and continue to use the GC10 for cadence. I have had a faulty GC10s in the apst do the same thing and just stopped using them for wheel speed and all good for cadence. The Garmin will use the GPS for speed if it detects no speed signal on the GC10.


This, i have a spare old speed/cadence sensor. Put it on a bike today, jsut for the cadence, but set up the wheel magnet as well. I noticed at 1km it was showing 500m, and at a point about 5km in it was showing 1km, so at the traffic lights, stopped, whipped off the magnet, everything back to normal straight away, cadence still works fine.
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