HRM 600 Avg GCT Balance off?

Hi all, the HRM 600 (61 grams) does weigh more than the HRM Pro Plus (52 grams) so it may bounce more therefore affecting data if the HRM is not fitted tightly enough. If you are experiencing this please tighten the strap enough before your next run and re-test. 

I think you are right. After tightening it more it has comparable data (except a bit higher vertical oscillation) to the Pros. The only downside is now it is more uncomfortable than the others bands  

Mine is already quite tight. Maybe even tighter than it should be. But I'll give it a try.

I was too fast to speak. Yesterday’s easy run was fine. Today’s tempo was ‘dear Lord’ bad. Look at this abomination!

Ok, tested with tightening the strap even more (I highly doubt the average user would default to wearing it this tight), and the balance % was even worse on today's run. I was averaging 3-4% off balance throughout the run, when I'd almost never go over 1% imbalance avg with the HRM Pro, HRM Pro Plus, and Stryd pod.

Yes it’s pretty terrible :( Hopefully it will be resolved soon.

I did two short comparative tests today, wearing simultaneously HRM 600 and HRM Pro Plus, each of them connected to a different watch. When then comparing both activities, most of the graphs match each other pretty closely, with the exception of the GCT Balance %, where there are differences up to ~5% most of the time. The red curve comes from HRM-600, and the blue one is from HRM Pro Plus. I've adjusted the strap of the HRM 600 rather tight in order to compensate for the heavier device - some 5 cm shorter than at HRM Pro.

The test above was a short jog on a flat road with a steady tempo (except of some short sprints at the very end). In the second case, it was a trail run on a accidental terrain, and with varying tempo. It was also longer (5 km vs 1.6 km at the previous one). Surprisingly, the curves from both HRMs seem to be matching each other much better (colors are inverted in this case: red - HRM Pro, blue - HRM 600):

It is obvious that there is a problem with the device.

I've never had more than a 1% difference between right and left.

HRM 600



HRM Pro Plus

Your graphs look like from two different runs. Each run can be completely different, so it is no good evidence. My graphs come from the same runs, where I've been wearing both HRM straps in the same time, and recording separately.

tolis77's runs might be different, but it is consistent with what others (including myself) are experiencing. I don't own the HRM Pro anymore, but it's clear something's off if I (and others) go from being within 1% every run to 3,4,5%+ imbalanced simply by switching to the new model. It's awesome that you were able to test to that extent and provide the data, so thank you for that.