race predictor

MikeM said:

I workout with both.

Every time?

No not every time with both, never both at the same time. I mean I use both. Sometimes I run with one, sometimes the other. My vo2 max changes and syncs between the 2 watches. My 7 day and 4 week loads sync, 

These race times don't sync, why not? I would think they'd be the same

Fenix 6 takes several things into account to calculate times including VO2max but also training load, length of long runs etc

Fenix 5 only takes vo2max into account

So which one is more accurate?

I guess you can tell yourself. For me the predicted race times were unrealistic with the fenix 5 and seems far more realistic with the 6X. I'm actually surprised about the accuracy of the predictions...

Thanks everyone. I ran the Detroit marathon in 4:08, in 2018. I haven't done any serious training this year, no long runs at all really. Maybe if i do some long runs with the 6 it would come down. 6 hours is not at all accurate for me.

Check that your max heart rate is correct (see device settings..then user settings). I recently found that mine was wrong. Once I corrected it, the race predictor began reporting values that make sense for me. For example, it is estimating 22 minute 5K...my last one a few weeks ago was 25:38, but I wasn't really pushing. And it's estimating a 4:02 marathon...my last one from a couple years ago was 3:54 when I was in a little better condition.

Thanks for the info. It has a MaxHr just above 220-myage. So it seems about correct. I seem to remember my 5Xplus at some point saying it detected a new max hr after a run, maybe it was after a lactate threshold run, I dunno, but at any rate it seems about right to me.

My race predictor numbers have changed since posting (not signficantly). All I did in the interim was log a walk around the block with the kids, so whatever the F6X is doing, it seems pretty dynamic. IOW it is changing often.

I actually prefer the old values because you knew exactly what you were getting: A very accurate estimate of what your aerobic fitness would allow you to do IF your legs could handle it. Most people are undertrained, so it was optimistic, but at least it was reliably and predictably optimistic. The new system is doing way too much guesswork. I also find the estimates to by implausibly slow. I have female teammates who run in the 2:40s, and they're freaking out about their watches telling them that they're only in 3-hour shape. These are people doing workouts like 10-mile tempos in 61 minutes, with high weekly mileage.