FR 945 accuracy of race time predictions

Thank you!

I’ve had the 945 for 4 days now. And did 4 runs varying distance. today I ran 12 miles and finished at 1:49. To my surprise Garmin 945 says my half marathon predicted finish is 1:45. Seems way off to me. Does the 945 need more runs to get a better predicted finish?

Yes, 4 runs are nothing .. imagine someone trying to evaluate your potential as a runner based on only four runs. The longer you have it, the more refined (and hopefully accurate) the results will be. Give it a few weeks.

Same applies to your VO2 Max estimate (an updated algorithm for that as well)

Thanks.  

So I just ran a 34:44 10k today, watch read 10.00km  It was an official race.  However my race predictor says 35:22?  The watch really knows nothing. 

The 5k says 16:46 which is probably close, the half is 1:18:13, which is too slow and the marathon of 2:47, which is the slowest.

My 935 was too optimistic sure but this doesn't help.   There's also no correlation to the ever changing VO2 max as the race estimators sometimes are faster when VO2 max goes down.  

The tiny watch you have on your wrist predicts your race time for a 10K within less than a minute accuracy and "The watch really knows nothing"?? As any experienced athlete knows any number of things impact how a race  goes, how you slept, what you ate, your general mood, your state of rest, the weather, the course, the crowd of other racers, where you start, etc etc etc

To somehow expect your watch to know and factor all this in is just wishful thinking and you might as well stop looking at any race predictions.

Your post shows a fundamental lack of understanding how computers and algorithms work. This is not supposed to be magic. To expect it, is unreasonable at any price.

I don't expect it to be accurate as a predictor but I do literally expect it to be at least as good as what I actually ran with the watch, which it knows as a recorded time for the distance. 

>10K within less than a minute accuracy

If you don't think "within a minute of accuracy" is a big deal on a 10k time then I question your experienced athlete status.  This has nothing to do with needing this to predict my paces. 

Again I'm not looking for predictions I'm looking for accuracy.   I like the watch for music and mapping,  Everything else ++ that comes with is just a toy.

I can understand your disappointment. There is a disconnect between the three things: VO2max based predictions, determined lactate threshold and personal records. Though I am not really sure how they could be factored into better predictions. Sure, if you were running your 10k PR slightly above your lactate threshold and the course was flat and weather was perfect, this could be used as a base for further estimates. But what about a hilly course on a hot day where you only ran for training purposes? And on a distance where you had no PR known to the watch before? Would need something to mark the run as „do not use for predictions“ then.

I can recommend Runalyze warmly for that stuff, excellent and free. Prediction for my last marathon within one minute. 15k race was within 30s.

GarminMarathoner said:

Again I'm not looking for predictions I'm looking for accuracy.

We do understand the frustration of not having your prediction line up with your race time exactly, but this feature is a Race Predictor. We have made many changes on the 945 to improve this by taking in multiple metrics such as VO2 Max and your overall mileage, but this feature is still a prediction. 

Your actual pace was 5:35 min/mi and our prediction was at 5:41 min/mi. Continued use of the 945 will only help these numbers align, but we cannot guarantee that they will every align perfectly.