Speed Displayed/Recorded at Twice the Actual

Speed Displayed/Recorded at Twice the Actual

Postby GrantYN » Sun May 21, 2017 5:54 pm

I've broken out the road bike finally and added a new Garmin Edge 1000. On my first two rides the Newton is displaying and recording speeds that are twice what the Edge is showing and recording. I factory reset the Newton and repaired the sensors. Still the same result. Obviously, I can't recalibrate the Newton.

Please help.

Grant
Newton
s/N 07-16-15-08-05-02-08-00-02-01-03-02-B8-7E-10-07
FW 5.15
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Re: Speed Displayed/Recorded at Twice the Actual

Postby Velocomp » Sun May 21, 2017 6:37 pm

1) Your speed data is showing dropouts. This is not a good thing...

2) With your bike at rest (not moving down the road), spin the rear wheel of your bike. What speed does the Garmin show? What speed does the Newton show? They should be the same.
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Re: Speed Displayed/Recorded at Twice the Actual

Postby GrantYN » Mon May 22, 2017 10:09 am

Thanks for the quick reply.

I've re-adjusted the magnet and sensor on the bike and did your suggested test on a repair stand. And, I paired my Garmin Forerunner to the sensor, too.

Interestly, both the Newton and Forerunner show twice the speed of the Edge 1000!!! However, I believe the Edge reading is more correct than the others.

I've checked the battery of the sensor. It's okay.

I've checked with a different speed/cadence sensor (the one that came with the Newton, but doesn't fit well on my bike frame) and they are all in agreement. I guess I'll have to try to figure out a way to mount the sensor on the frame.

Grant
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Re: Speed Displayed/Recorded at Twice the Actual

Postby texmurphy » Tue May 23, 2017 7:19 pm

The Edge 1000 is most likely in wheel size auto-calibrate mode. The Newton has you set the wheel diameter and I assume you also did this with the Forerunner. And your wheel size is what it should be.
Do not let the Edge auto-calibrate the wheel circumference, rather you should manually set it.
The Edge will otherwise attempt to set wheel size every time you start a ride and may get it (very) wrong if it has a bad gps lock.
I do not have an Edge 1000 so you should read the manual to figure out how to do this.
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Re: Speed Displayed/Recorded at Twice the Actual

Postby BBQcyclist » Thu May 25, 2017 1:00 pm

Hmm.
I dont think the Edge 1000 will get speed (very) wrong, as it can simultaneously rely on the remote sensors - either magnetless or w magnets.
I hve a 1000, w magnetless sensors.
Speed is bang on previse, compared to another on-board old-fashioned bike computer.
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Re: Speed Displayed/Recorded at Twice the Actual

Postby texmurphy » Thu May 25, 2017 5:13 pm

If satellites are not acquired before moving and the Edge decides to calibrate the wheel size, then you can get very wrong wheel circumference.
Best to manually set the wheel size. A variance of 1 or 2 mm on the circumference will have negligible impact.
Besides, if doing strava stuff, then the speed is computed from the gps trackpoints.

If wheel sensor is present, then the 1000 will use the wheel sensor and not gps for speed.
The wheel size for the Newton is set manually which is why it agrees with the Forerunner. The Edge 1000 setup for wheel sensor should reveal the wheel size it is using. Easy to compare it to the Newton's set wheel size.
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