Speed discrepancy between Garmin 800 and Strava?

Hindmost

Hi,

I completed my morning training laps yesterday then uploaded my data onto both Garmin Connect and Strava. For this ride, Garmin gives my max speed as 48.2 kph but on Strava the max is 53.3 kph. That's a significant difference.

Does anyone know why this is?

Do you know which reading is more reliable?

Thanks in advance.

cougie

I'd go with the garmin - mine takes out readings that are clearly bobbins - but strava doesn't.

sigorman85

Strava speed gps? Garmin wheel magnet ? Might be why

madasahattersley

If I were you, I still wouldn't give a toss.

Bozman

I've give up on any comparison between the two after noting the vast discrepancy between two devices on the same ride.
We were having a bit of a comp to see who could climb the most during a month, when we compared data on Strava from one ride there was roughly 30% discrepancy between the various Garmins, joke.

Hindmost

Thanks for the feedback. I'm not so bothered but I am surprised more people haven't made a fuss about this as I'm sure a lot of serious amateur cyclists use both to monitor their progress.

sigorman85 wrote:

Strava speed gps? Garmin wheel magnet ? Might be why

I don't have a wheel magnet or anything else attached to my bike that would interfere with readings, just the Garmin unit.

tangled_metal

I think he was meaning if you use a bike computer that takes ths distance measurement by a sensor measuring the number of times a magnet on your wheel passes it then converting it via your manually entered wheel cicumference into distance travelled. That was the old way of measuring distance before GPS and is actually more accurate when you consider how GPS actually works.

In case you didn;t realise you can be sitting still and you GPS is capable of suddenly putting you several metres away, even straight up!! I believe some units might be able to remove spurious GPS results but generally comparing units is very inaccurate. It is virtually impossible to get two GPS units to place you axactly the same location on a ride so up to you which you believe is right. Truth is neither is going to be exact. If you doubt me look at the tracks on a GPS review on DCRainmaker.com website. He often comments on the inaccuracy of the tracklog of a GPS watch on review by comparing it with a competitors product that followed the route better. GPS is notorious for its wobbles so really don't worry about it. If you wanted accurate speed and distance get an old fashioned bike computer as a backup!!

mfin

Hindmost wrote:

Thanks for the feedback. I'm not so bothered but I am surprised more people haven't made a fuss about this as I'm sure a lot of serious amateur cyclists use both to monitor their progress.

sigorman85 wrote:

Strava speed gps? Garmin wheel magnet ? Might be why

I don't have a wheel magnet or anything else attached to my bike that would interfere with readings, just the Garmin unit.

Just for more info for you, I do have gsc10 sensor, and with my Garmin 500, max speeds on rides always show higher on Strava than Garmin Connect. Max of about 48.5mph on Garmin would show about 51mph on Strava for example (from memory), the discrepancy is always there on every ride I've ever looked at.

Hindmost

Thanks again for the feedback - much appreciated.

sigorman85

I think with the elevation you can manually zero it to sea level when at sea level to give it more of a accurate reading not that it should be out anyway

barrowmatt

My 'theory', could be bobbins though, is that Strava maps to segments following the road map. Therefore if you apex some nice downhill bends you can shorten the actual distance travelled so Strava will think you went further in the same time (tracking based on the centreline of the road).

Just a theory but yes I've seen segment average speeds on Strava faster than the overall ride Max Speed for fast downhills. :?: :?: :?:

wongataa

barrowmatt wrote:

My 'theory', could be bobbins though, is that Strava maps to segments following the road map. Therefore if you apex some nice downhill bends you can shorten the actual distance travelled so Strava will think you went further in the same time (tracking based on the centreline of the road).

Just a theory but yes I've seen segment average speeds on Strava faster than the overall ride Max Speed for fast downhills. :?: :?: :?:

This: http://blog.veloviewer.com/41mph-the-evidence-against-the-sunday-times-article/is the real reason of that strange data in Strava.

Hindmost

wongataa wrote:

barrowmatt wrote:

My 'theory', could be bobbins though, is that Strava maps to segments following the road map. Therefore if you apex some nice downhill bends you can shorten the actual distance travelled so Strava will think you went further in the same time (tracking based on the centreline of the road).

Just a theory but yes I've seen segment average speeds on Strava faster than the overall ride Max Speed for fast downhills. :?: :?: :?:

This: http://blog.veloviewer.com/41mph-the-evidence-against-the-sunday-times-article/is the real reason of that strange data in Strava.

Interesting article and it sheds some light on why I see some segments around Regents Park apparently being completed at well over 120kph by some cyclists. To put this in perspective, the world record cycling speed on flat ground, unpaced, is around 135 kph, if I recall correctly.