Different distances/speeds on devices

[awesme]

Hi guys

 

For a while now my Garmin have given different trip distances compared to my fiancé's Topeak 130, always though/blamed the Topeak. But today we got her to load GPSLogger2 and record the ride, again her distance is 10.5km where the Garmin recorded 9.6

 

Anyone have an idea where the problem might be coming from.

 

I've set the Garmin to auto tune, other words I did not specify a wheel size (there was no size that matched the 26 inch wheels) so told it to learn by using rotations from wheel in combination of the GPS sensor.

 

G

[Minion]

I've set the Garmin to auto tune, other words I did not specify a wheel size (there was no size that matched the 26 inch wheels) so told it to learn by using rotations from wheel in combination of the GPS sensor.

In my experience, auto-tune sometimes gives some funny results. It also sometimes takes a while to decide on a wheel size (and takes some pretty weird guesses while doing so).

 

It's generally better to choose the wheel size based on a weight run-out test (get on the bike and measure how far it goes for one wheel revolution).

 

 

You can also use a program like Sports Tracks that gives both the GPS distance and the wheel sensor difference. It's pretty simple to adjust the wheel circumference until they're the same.

[awesme]

Think I found problem, did a wheel measure quickly from valve to valve with me on bike 2003mm, Garmin had 2096 set, so changed now, will see how it all works out now.

 

thanks.

 

G