Heart Rate, how do you reconcile setting it to a value, and yet "auto detect" still shows?

You need to turn auto detect off to maintain the value which you have set.

If you have set the Max HR value to 170 bpm, the the algorithm has not detected a higher value.

As an example my data says.

Maximum

164bpm: Auto Detect Off 

In my case I set this in connect and not on the EDGE, doing it this way propagates the same values to all of my devices. If you only have one device then its fine to set it on the device.

Great thanks much, i'll turn it off!

Also beware that as there is not much difference to a 530 and works very much the same, you can find that the Edge will change the values that you have set and you will not know until you ride.

Why it does it, no one seems to know, it has been reported before and it is very annoying when it happens. Sometimes it will happen after an update, but doubt the Edge 530 and 830 will ever get updated again as they seem. Also I have found, just opening the heart rate zones page for just a look at to see if everything is OK and closing the page down will do it and you have not even done anything to it.

But, it happened to me again last week, I have 195 BPM as my maximum, both "Auto detects" are turned off, I ride downhill from setting off, short turn to the left and go up a gentle hill and I'm in the "red zone" in less than a minute with no effort. When I stop and look, my maximum has been changed to 152bpm and then I have to change the value back to 195 BPM.

It is very annoying. So basically, keep an eye on it.