Suunto Race S optical heart rate sensor accuracy
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Hi everyone,
I was wondering if someone can share some further experience regarding the new optical heart rate sensor accuracy on Race S when running. Being aware of all the possible variable influencing it, nevertheless my own experience is pretty bad. Under the same conditions, sometime it is giving correct values for a couple of KM at the same pace and then getting crazly high for the rest of the run, or it starts bad, then stays right for some km and then get again bad in the end.
I’m of course not expecting the precision of a Polar H10 chest heart rate sensor, but coming from a Garmin Instinct Solar 2, the Sunto Race S wrist optical heart rate sensor in comparison is a mess, at least for me.
Any feedback is appreciated.
Thanks
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@dariof I observed optical HR behavior that can be characterized as cadence lock.
On two occasions when trail running, when hiking up a steep grade, HR was stuck at 60-80 bpm for long periods of time, which is very close to step rate. Also, on few occasions when running it was jumping up to 160-180, which again is close to step rate.
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@dariof yep, my experience with the Race S hasn’t been good at all. So it’s permanently paired to either my H10 or my Verity Sense. My old Instinct (original) was actually really good as was my Fr245 Music which was probably the best OHR I’ve ever come across. But the SRS is still a fine watch with many great attributes.
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My experience with the Race S OHR is very good, better than S9 Peak and S5. But I have no Garmin to compare and wear the watch tight above my wrist
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I just bought a Race S and am having problems with the heart rate accuracy, it seems to read double my actual heart rate when resting. I use an external sensor for activities so not sure how it would stand up then, but the resting rates are often way off. Shown here alongside the Pace 2 that I was upgrading from which is reading accurately.
I’ve tried everything I can find, soft reset, hard reset, toggle 24/7 monitoring, tighten, loosen, move watch, downgrade firmware to previous version, nothing seems to solve it. Do I have a faulty watch, is it a software issue that will hopefully be solved at some point, or is it innate to the sensor and will likely always be like this?
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@RdoubleC I don’t think yours is faulty, mine has always been absolutely junk as well. Last night reading 85-90bpm when my actual HR was in the 40/50s.
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Even if some OHR may work better here and there, also in other brands, this is an infinite debate.
On me I’ve never found from now any good OHR for intense activities. For daily use, sleep tracking… it works very fine.
Whenever I want accuracy (trail running, cycling…), I use the HR belt.But regarding Suunto OHRs, they’ve been improving over years (S9b <<< Sv < Srs). On me the SRs works better, but Not a very big difference with my SV.
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@dariof The Apple Watch is supposedly the best OHR out there. For me an AWU works OK on easy, sustained runs. I always have some OHR dropouts and on intervals AWU is not good. Suunto OHR for me is worse. I always wear a belt for exercise. However for 24/7, sleep and not exercise I find Suunto and Apple identical.
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did you resolve this? I have the exact same issue - i can compare to my garmin or just check my own pulse and the Suunto is regularly 2 times actual…
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If Suunto is unable to provide a better WHR accuracy, then Suunto should at least support multiple sensors.
Personally I can’t wear a chest sensor during longer events. I get skin irritation on the chest to the point of bleeding. I guess that is because of salt accumulating in that area and compression straps of hydration vest moving the chest sensor. I started using Coros armband HR sensor, and it is very good, but it doesn’t support ZoneSense. A good solution would be to use an armband HR sensor for longer events and a chest HR sensor for shorter runs and workouts, but that is impossible without constantly having to re-pair the sensor.
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@Brad_Olwin I have the same bad experience with OHR while running on my newly bought Suunto Race S and I just return to the dealer for checking. It give me the inconsistent heart rate data, sometimes it bump up very high and some times no heart rate signal while I still maintaining the steady speed on the flat road. This morning, while seating at the office, My heart rate should be in normal range 45-50 but it is bump up to 90 - 100 ad I cannot measure the SPo2 on my watch, I tried to measure SPO2 several times and it says it is only 70 which is super ridiculous. I feel sad then go to Suunto Vietnam directly after that, now i need to wait for their check.
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@RdoubleC May I know how is the heart rate on your watch now. I got the same issue as you and now I am waiting the answer from Suunto Vietnam after leaving my watch there one week for checking.
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@TuanNT said in Suunto Race S optical heart rate sensor accuracy:
This morning, while seating at the office, My heart rate should be in normal range 45-50 but it is bump up to 90 - 100
While reading this I decided to check what my Race S is currently showing as I am taking a coffee break at work. The watch is showing 120-140 while I am sitting still and my pulse is clearly about 50 - I have manually counted it. This is ridiculous!
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B brechtvb referenced this topic on 3 Apr 2025, 08:56
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@sky-runner My first impression was that the heart rate accuracy was good. After buying the watch, I went on holidays and used the watch mostly for intensive hiking.
When back home, doing circuit training I noticed the heart rate sensor was displaying half of what I expected it to be. I ordered a new watch strap from Hirsch, model vocem, which better keeps the watch correctly positioned. Accuracy has well increased and I rarely notice heart rate drops