Forerunner 255 Series - Recent Threads

Forerunner 255 stops showing heart rate and discharges very quickly (from 100 to 10 within hours) after the update

1299652 — Mon, 20 Jul 2026 09:45:57 GMT

Yesterday i updated my Forerunner 255 to the last version (28.05). After that it started discharging very quickly and then the green lights of heart rate monitor stopped. And the heart rate isn't displayed on the watches. I did reset - this didn't work. Connected to my PC with Garmin Express software - also no result. The Garmin PC shows that all the updates are installed successfully but the heart rate monitoring function doesn't work

Garmin Coach: Final recovery interval skipped before Cool Down

Arno — Sat, 18 Jul 2026 18:05:44 GMT

During Garmin Coach interval workouts, the software systematically skips the final recovery step after the last fast interval. The watch immediately switches to Cool Down. This is physically frustrating, as a recovery phase is highly needed right after the final hard effort before entering the actual cool-down pace. Please fix this logic in the workout loop so that the last recovery step is executed properly.

Thank you in advance,

Arno

RE: Garmin Coach: Final recovery interval skipped before Cool Down

Arno — Sun, 19 Jul 2026 08:01:34 GMT

Hey, I can confirm that this happened in every interval workout I did with the Garmin Coach (more than 20 times).

RE: Garmin Coach: Final recovery interval skipped before Cool Down

Garmin - CF — Sat, 18 Jul 2026 22:15:42 GMT

Arno Hi, there! Can you confirm if this has just happened once or does this consistently happen with the Coach plan?

BUG: Activity Clock Data Screens UI Issue

2856561 — Thu, 16 Jul 2026 00:55:19 GMT

Hello,

I got my hands on a Garmin Forerunner 255 Music 46mm.

I started an indoor walk activity (should be similar to any other activity) and navigated to the clock data screen.

When I have too many "icons" active (battery, phone connected, alarm active, headphone paired), they seem to be cut off at the edges (see below). If one of the icons is removed, it looks fine.

Heart rate error - Forerunner 255 Series - Software Version 27.09

5639340 — Wed, 03 Jun 2026 13:11:17 GMT

Hi
Yesterday, twice during a 1 hour and 23 minute bike ride, my heart rate fluctuated twice. Normally it doesn't go above 180 bpm (I have an alert to notify me when it reaches 180 bpm).

And yesterday it reached 214 bpm, then I stopped the bike and suddenly the heart rate dropped to 135 bpm. This happened twice at different times... See the attached photo.

Forerunner 255 Series - Software Version 27.09

drive.google.com/.../view

RE: Heart rate error - Forerunner 255 Series - Software Version 27.09

ovekvam — Wed, 15 Jul 2026 17:39:51 GMT

Mine is still working well like before on steady runs. As always, fast intervals starting from a "low" heart rate is too confusing for the wrist sensor. With a chest strap, it is always spot on.

RE: Heart rate error - Forerunner 255 Series - Software Version 27.09

7157803 — Wed, 15 Jul 2026 15:37:53 GMT

Just to add to this thread I have a two years old FR 255, been great up to now. Wrist HR monitor may be less accurate than a strap but at least it has been consistent with itself and allowed me to judge effort especially in longer runs. Eg in Edinburgh marathon in May it was hot, noticed HR was about 10bpm higher than normal and adjusted pace to maintain effort. Since June (?after last update) HR has gone mad. Typically races up (200bpm) at the start of even a gentle run then drops off a cliff to normal levels at around 1.5-2 miles. Playing havoc with my recovery stats, V02 etc. is it time for a new watch or do we need another update from Garmin?

RE: Inaccurate display of navigation curve

Luděk — Wed, 15 Jul 2026 12:28:24 GMT

Garmin, can you please respond to the 4 points of my response, or at least the last one?

Inaccurate display of navigation curve

Luděk — Tue, 07 Jul 2026 22:49:51 GMT

I was unpleasantly surprised by the way the watch displayed a navigation curve of about 44 km in length, with 1671 points (19 of which were duplicates) on the route, i.e. <trkpt> elements in the GPX source file - unfortunately, it cannot be attached here. There was a significant deviation in direction at the start and in several other places the turns were "cut off".
The Czech support recommended that I divide the route into maximum eight-kilometer sections of about 300 points, which seems very impractical and unusable for estimating the arrival time at the destination (ETA). The support did not want to tell me under what conditions this distortion occurs. I noticed that in this case the watch probably reduced the sequence of points by selecting every three and a half points (they took this half as the middle between two neighboring points).
I honestly don't understand why this reduction is performed when the watch is able to correctly display (with a black line) a significantly more detailed, actually traversed route of this activity with 5553 points (exported via the Garmin Connect website). I understand that for some navigation calculations (e.g. checking for deviations from the route or estimating ETA) the watch is suitable for a simplified route, but for displaying the navigation curve they can perhaps leave the points unreduced.
Moreover, the Garmin Connect web application, into which I import the GPX file to create a route and then upload it to the watch, does not warn about the reduction in any way, or does not perform any more sophisticated reduction (e.g. Douglas-Peucker) itself, if it were really necessary. Without precise knowledge of the watch's limits for unreduced display, I cannot externally edit the source GPX myself.
Garmin, would you please comment on this? And do other users have any experience with this?
Thank you.

Pace zone Table/Chart- Request

7174720 — Tue, 14 Jul 2026 02:02:25 GMT

I wish to see garmin add at least "Pace Zone" chart/table like Cor*s watches. I think don't need to say that they have very bad app design and every time I've been losing myself in it. Not; I'm not eldery, 30 y.old IT tech guy.

Charging Port Question

Jacquers — Tue, 07 Jul 2026 13:22:27 GMT

The charging cable my watch shipped with was very tight, but has already loosened a bit. I've seen posts about ports coming out on other older models and I'm concerned that it might have pulled too much on the port. I noticed what seem to be gaps and a small (metal?) part between. Can anyone else please check if theirs look similar? Thanks [emoticon:c4563cd7d5574777a71c318021cbbcc8]

RE: Charging Port Question

Jacquers — Fri, 10 Jul 2026 05:53:44 GMT

Thanks for checking and posting photos 🙂

Looks similar, so I think mine is ok. The metal part I was referring to is right at the bottom, below the tab that clips into the cable.

RE: Inaccurate display of navigation curve

Luděk — Thu, 09 Jul 2026 23:42:09 GMT

This would also correspond to my observations - I don't see any problems with navigation with the watch on shorter routes (either the route doesn't deform at all or only slightly). But on the mentioned route it was already clearly visible in several places. It's a shame that the GPX or FIT file in question cannot be attached here - I don't understand this limitation here either.

RE: Noisy GPS day doubled length of Ultratrac activity

6125703 — Thu, 09 Jul 2026 23:03:32 GMT

I'm aware of these basics and "theory".

To be more explicit, I am wondering if anybody knows what in practice leads to such day-to-day qualitative change in the amount of GPS drift or inaccuracy for the individual location fixes.

I walked the same route each day, with the same houses, yards, tree cover, etc. None of the explanations like urban canyons etc can account for the difference between one day and the next.

And, the error seemed consistent through the entire walk, with 1 mile auto laps alerting steadily. Not some individual glitch or local source of interference like a house or vehicle.

Is there some kind of global GPS jamming or spoofing happening these days? Or is there some other more natural explanation? The bad results was recorded yesterday evening 7/8 in local California time.

Noisy GPS day doubled length of Ultratrac activity

6125703 — Thu, 09 Jul 2026 18:28:58 GMT

Had another one of those absurd days where my FR255 had really poor quality GPS fixes and over estimated distance.

I walked the same course three days in a row using Ultratrac. It is very close to 3 miles and the first two days did well enough, measuring roughly 2.9 miles with little visible deviation in the map trace.

The third day, I got 1 mile auto-lap alerts way too soon and it ended up measuring over 6 miles. The trace even on the watch screen shows crazy deviations. Like a drawing of the map from someone suffering severe tremors/seizures. Lots of back-and-forth and lateral scribbles.

These were in suburban SF Bay Area in California, so nowhere near any contested zone where you expect GPS denial etc. I wonder what is the most likely explanation for such huge day to day difference in quality...

FWIW, I was doing these to assure myself all was well with the watch after updating the firmware over the weekend. Since it worked normally the first two times, I doubt it has anything to do with the firmware update.

RE: Inaccurate display of navigation curve

Luděk — Thu, 09 Jul 2026 22:09:52 GMT

Thank you for your response Garmin, Czech support also told me something similar. But I don't understand:
1. Why can't the watch correctly draw the navigation route when it can correctly draw the actual route (black line), which in my case was a little longer than planned and with more points (5553 compared to 1671)?
2. Why is Garmin Connect unable to announce when preparing the route whether it will be reduced by the watch (and possibly show how) so that the user knows whether he can rely on the navigation, which can be a matter of life or death?
3. Why doesn't Garmin Connect adjust the route in some more intelligent way (e.g. Douglas-Peucker algorithm) than the watch probably does with the sampling mentioned above? Garmin Connect, whether web-based or as a mobile application, generally has more power than the watch for this.
4. And if you can't or don't want to fix any of the previous points, why don't you at least publish the exact criteria for when the watch will reduce the route so that the user can take this into account and possibly adjust the route themselves?

RE: Noisy GPS day doubled length of Ultratrac activity

Garmin - KS — Thu, 09 Jul 2026 21:32:07 GMT

UltraTrac Mode is designed to extend battery life by reducing the GPS recording rate, and as a result, track detail and distance accuracy can be reduced compared to standard GPS recording. For additional information, visit Setting a Garmin Watch to UltraTrac Mode for Longer Battery Life

GPS drift and other factors can also affect GPS signal quality and impact recorded tracks and distances, as explained here: Top FAQs About GPS Distance, Speed, and Pace Accuracy With Garmin Devices

When GPS positions become unusually noisy, the reduced sampling rate used in UltraTrac Mode can increase the effect on the recorded activity. The map behavior you described is consistent with poor GPS positioning during the recording.

RE: Inaccurate display of navigation curve

Garmin - KS — Thu, 09 Jul 2026 20:58:00 GMT

Luděk The behavior you're seeing may be related to course limitations on the device. Garmin watches have limits related to course points and course calculation, and long or complex courses may require splitting into smaller sections. If you're working with a very detailed course, reducing its complexity or dividing it into smaller segments may help avoid course-related limitations.

RE: Inaccurate display of navigation curve

6125703 — Thu, 09 Jul 2026 19:46:04 GMT

FWIW, I downloaded my longest course (about 27 km) from Connect as a FIT file and used fitdump to look at it. This was one I created on Connect itself. This one worked nicely on my FR255 during the actual hike.

It seems like it has about 839 "record" entries which I think are track points. Then just a handful of "course_point" entries which I think were waypoints I labeled on the course editor like water crossings.

When I download the GPX version, it also has 839 "trkpt" records in it.

RE: Inaccurate display of navigation curve

Luděk — Thu, 09 Jul 2026 19:15:27 GMT

I guess I didn't express myself completely clearly: Displaying only points from the GPX file connected by straight lines would be enough for me, so I don't see the source GPX file as incorrect or insufficient, just like the FIT file generated from it. I don't see any problems with shorter routes or with displaying them on the watch, I just came across the described problem now. Czech Garmin support confirmed this problem to me, but they said they can't give details under what exact conditions it occurs.
That's why I'm trying to draw attention to this problem on this forum, because the watch manual is silent about it and Garmin Connect doesn't warn about route reduction in a specific case when preparing (importing) such a route, which I find annoying and in a sense even dangerous. Moreover, as a programmer, I don't really understand why the reduction has to occur.

RE: Charging Port Question

6125703 — Thu, 09 Jul 2026 19:08:30 GMT

(I deleted my earlier post because I did manage to get some photos to focus here eventually...)

The metal part in the middle looks like part of the retention system for the cable, not related to the interface with the watch plastic.

What I see at the bottom looks like some molded plastic contours beneath or behind the metal port. It's hard to really imagine how it is mounted and what exactly penetrates versus being surface mounted?

RE: Inaccurate display of navigation curve

6125703 — Thu, 09 Jul 2026 18:21:06 GMT

The fact that it can display courses just fine tells me it is a problem with the initial data or the conversion process. Maybe the GPX points don't get translated into the right point type in the FIT file? Not all FIT files are equivalent. The FIT format is capable of storing points of different types, some defining the course line and others defining waypoints or adjacent landmarks.

Also, I think traditional GPX file usage may be sparse and assume additional routing during display. So it is key waypoints along the way but expects the display to fill in the gaps with knowledge of terrain or trail networks.

For a device like FR255, there is no supporting map. So it will only draw straight lines connecting the points. A good course is going to have a high resolution series of points quite close to each other to trace out the full shape of the route.

RE: Inaccurate display of navigation curve

Luděk — Thu, 09 Jul 2026 09:04:21 GMT

I downloaded the FIT file saved in the COURSES folder on the watch and tried to re-import it as a new route in Garmin Connect - it looked undeformed, the same as the original source GPX file.
So I see the problem in the way the watch displays it. Supposedly, more powerful Garmin models are better.

RE: Inaccurate display of navigation curve

ovekvam — Thu, 09 Jul 2026 05:19:10 GMT

I make courses for the FR255 with Strava. Very nice editor.