24.18 and 24.19 Grade % wildly inaccurate

On both of our 840s and my 540, 24.18 and 24.19 grade information is inaccurate and very jumpy. Today's ride was on a Rail-Trail, so I know the grades are long and very consistent. The Edges will show a descent when we are clearly climbing and the values jump all over the place. Worst example was a long 2% climb, which Edge beta prior to 24.18 correctly identified. 24.19 identified the grade as -4%, yes, a 4% descent.

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MartinC700 3 months ago +5

Totally agree, before this update the grade was very laggy but essentially accurate. Now it's all over the place, sometimes it represents the grafe well, other times it jumps around like crazy. For example…
Todd727 3 months ago +2

I forgot to add, Climb Pro has these climbs in the database. Climb-Pro correctly shows what the grade should be, but Edge shows the crazy numbers that don't match.
1311649 3 months ago +2

I had the same problem today, doing a climb I know with my eyes closed and at a point that is 14/15% it showed 5/6% I was soooo mad as this Garmin is two weeks old!!!! GARMIN FIX THIS RIGHT AWAY!! We are…

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0 Martin Borsje 1 month ago in reply to 2888722

Support is apparently not diving into the matter and follow routine.

0 Martin Borsje 1 month ago in reply to F._Lara

Already more than 20 years ago, hardly digital, almost analogue bicycle computers, e.g. Cateye could indicate grade etc. quite accurately. With the more modern (Bosch) sensors with way higher accuracy and response speed this should be a walk in the park (apart from the water in the hole issue, which is a hardware design flaw). I really don't know why the software routines behaves that badly.

0 F._Lara 1 month ago

I guess it's not possible to downgrade to firmware 24.17, right? Just to make sure it's the firmware and not the hardware.

0 Martin Borsje 1 month ago in reply to F._Lara

I am almost absolutely sure it is a firmware problem and not a hardware problem. The hardware problem, I discussed earlier somewhere in this forum, is caused by the water in the hole issue (port to the barometer blocked by foreign matter as water, sweat etc.) but this behaviour is software related as the behaviour changes with every firmware upgrade and I observe it with my brand new 840, which I fanatically keep dry.

As I mentioned somewhere else in this forum (too many topics on the same issue): if at the start of a climb I observe the elevation increasing (fully expected when climbing) and at the same time the calculated grade at -1 % or 0 % I can only conclude there must be something wrong in the algorithm to calculate the grade. The sensor only gives a pressure signal, of which the elevation is calculated. The grade value is as well using the travelled distance of the bike (grade = delta elevation/distance travelled).

To filter out noise in the calculated grade (and total elevation gained) by e.g. small bumbs, vibration, traffic-calming measures a software "low pass" filter is applied for both calculating total elevation gained (not every 20 cm of a traffic-calming hump should count) but as well a low pass filter for the calculated grade (you don't want to see the grade change every 0.2 s). The filters are not the same. Apparently, Garmin is doing something wrong in engineering and implementing these software filters, although the technology is already over 20 years old.

0 F._Lara 25 days ago in reply to Martin Borsje

The latest firmware update (v25.24) fixed my unit and the grade measurements seem reasonable to me.

0 gazzafry 5 days ago

25.25 is no better. A 5.2km climb shows as Starting when already 2km into the climb. Previous software versions would show that the climb has been completed with still 700-900 mtrs to go. If only Garmin would acknowledge that they do have problems rather than implying that it’s my fault, we might be able to make some progress, but it appears you can’t help Garmin to help its Users.