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Constantly incorrect altitude gain

Hi all,

It seems that my Edge 520 constantly shows the incorrect altitude gain, the gain is considerably less than it should. I've compared my logged alt gain with two other EDGE 520 computers on the same ride, and it's 20%-30% lower. I've compared the data directly in the units, in Garmin Connect and in Strava and it's all the same, meaning that the altitude gain data is not altered by Strava/GConnect. For example, on a recent ride (60km), I showed 580m alt gain while my GF showed 690m. According to the Strava elevation data, my GF is more correct.

In the last ride, I checked the present altitude in the start, and in the pauses, and it was almost identical all the time. At another time I manually corrected my unit, to make it match exactly with the comparable units I had, in the start.

I started with the pre-set "Smart" measuring, and changed it to a forced 1-sec interval recording, without success. I can also mention that we use the same firmware.

Does anyone have any idea what else I can do/check before I send it to Garmin?

Thanks in advance!

0 Former Member over 8 years ago

Pressure change due to changing speed affects the total gain value, especially on rides with a lot of short up and downs. Where you all riding pretty much at the same speed? Is there any difference in where and how the 520s are mounted? If there is any difference in the mounting try swapping 520s with your GF to see is the problem stays with the 520 or the mount.

0 Mklmtb over 8 years ago

Thanks for the reply!

Regarding the speed, when I go on rides with my GF I tend to ride fast and wait up, but the same difference also occurs when I go on rides with friends. Yesterday I did a 2h MTB ride with a friend and the difference was 210m vs 290m altitude gain (he uses an Edge 810).

I'm seeing the same difference both on my MTB and my Road bike unfortunately, so I don't think it matters. I've even moved my road bike mount to another position, just to make sure.

I uploaded two FIT files to velohero, just to make a review of the altitudes, and it is pretty clear that the top graph is much more "smoothed" out than the bottom one. This one is for a ride I did with my GF, zoomed in to only cover the first 4 minutes when we biked next to each other at the same speed. See the link below.

0 Former Member over 8 years ago

Check the pressure port hole for anything blocking it. It's the small hole on the back side just ahead of the mount. If that is not the cause contact support about a replacement.

0 Mklmtb over 8 years ago

There is nothing obvious that is stuck in the hole located just above the serial number sticker, I don't really know how I possible can clean it though, I've tried to blow some air into it. There are also 4 small holes in the middle of the circle, used for the mount, and I've tried to clean those too as much as I possibly can.

I have contacted support, they recommended a total reset, which I just did. I'll go for a new ride the coming days and I'll try to check it then, if there isn't any improvement I'll ask for a replacement.

Thanks again for your assistance!

0 Mklmtb over 8 years ago

It seems that the issue was resolved by doing a total firmware reset, plus 20 minutes in the garden to really sync up the satellite data afterwards (it took almost 15min for it to get the correct altitude).

Unexpected, but good that it worked:-)

0 Former Member over 5 years ago

I've been having the same problem. I've tried hard resetting it, twice, and it hasn't worked. Also, the hole above the serial number has been cleaned out by compressed air.

I'd really hate to have to send it back to Garmin.

Any suggestions?

0 Former Member over 4 years ago in reply to Mklmtb

Hi There - I'm having the same issue. With +10% difference compared with fellow riders on a consistent basis. Per your post above, how did you perform a total firmware reset? What did you do? Thanks

0 Former Member over 4 years ago

Having exact same issue, and it gets much worse over long distance Today road side-by-side with a friend on a 61 mile ride. He had 10,000+ of climb, which what was expected looking at strava segments, But I only had 8,500. He's using a Wahoo Element Bolt. Considering switching brands to get more accurate date.

0 HughFeeley over 4 years ago

I also have the same issue with my 520. I did a 1800m gain spin with a group of lads last week. Most using 520s but a few Wahoos. All have elevation gains ranging from 1600m to 1900m while I had 700m. Again today we did 1100m. My 520 recorded only 520m gain. Both spins had <50% of elevation gain recorded which is much worse than usual. It's always underestimated but not by this much. I've cleaned the port and reset but nothing works. Very frustrating.