"Zwifters Nearby" lead/lag times are unexpected

See the attached image for details. I was 58 seconds from the end of a workout interval. The end-of-interval circle is displayed in the minimap. That circle is quite accurately positioned. Also displayed in the minimap is the position of the rider ahead of me (R. Jajodia). Note that R. Jajodia has already passed my end-of-interval circle. This means that R. Jajodia is more than 58 seconds ahead of me. Yet, on the “Zwifters Nearby” list, R. Jajodia is reported as being only 19 seconds ahead of me. That’s just not possible. Even though R. Jajodia is stationary, I can only reach them in 19 seconds if I speed up to three times my current velocity.

I’ve circled the relevant parts of the image in yellow.


I have noticed the same problem.

Times are quite often inaccurate. If you are racing, the times will especially shift when both riders are going uphill or downhill. I find that going uphill, the time gap is often double (the screen says two minutes but it is actually four minutes.) and going downhill it is half (the screen shows two minutes but it is actually less than one minute.)
To verify this (not in workout mode) click on the rider ahead, note their exact location, and stop-watch how long it actually takes you to reach that location. The Alp is the best spot to test this out. I think on a flat course, it is accurate.

I noticed the issue in situation similar to Siobhán. Doing a workout around Tick-Tock, the arch appeared on the map a minute up the road, with the nearest rider beyond that point. The Zwifters Nearby gap told me that I was only 15 seconds behind. So it doesn’t appear to be any more accurate on a nearly perfectly flat course.

I’ll grab a screen shot the next time.


I didn’t mean to suggest that this was only a problem with workout mode. It’s just that workout mode gives nice reference points for the screenshot.

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In workout mode, there should be no needed references to other riders unless you are in a group workout. It’s really only in races that you want to know where you are in relationship to other riders.

True: But I think the OP was using workout mode to show that the time behind or in front of another rider is inaccurate.

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Also, an important point illustrated by workout mode is that Zwift knows exactly where I’m going to be at a given point in the future, given my current wattage output.

According to bikecalculator.com, I’d have to increase my wattage to 427 watts to reach my end-of-interval marker in 19 seconds (making a lot of simplifying assumptions).

It’s quite possible that I just don’t understand the lead/lag times reported here. It may have been a conscious design decision not to tie them to a particular rider’s effort, so that they don’t go up and down as your power output changes. For instance, you wouldn’t want the lead times to go to infinity if you stopped. Maybe these times are calculated assuming a constant 6 w/kg? I’d be curious to hear from someone who actually works for Zwift and knows the answer.