Time Gap very wrong


I have asked before can the time gap be corrected in Zwift. Its pretty basic physics and it is used in everything from formula one racing to… well everything else except Zwift. A second gap is a second gap  at 5 kph to 300 kph and beyond. The distance is greater or less but the time remains the same. So when I get to the top of the climb on Zwift with a 10 second gap why  does it grow to over a minute immediately when we are on the decent.  If I pass point A at 5 kph and the rider behind passes that  point 10 seconds later, then down the hill I pass point B at 70 kph the rider behind passes point B at 70 KPH the gap should still be 10 seconds if we have matched speeds. Not over a minute. 

Maybe the gap increases as you are on the decent and the rider behind is still climbing? That then mimics real life. Then when you hit the bottom and slow down the rider behind is still descending and the time gap comes down again.

I think in car racing the time gaps are measured on passing the same point. In Zwift the app is having to do some calculations based on what’s to come and at the current power level. It’s only a guesstimate.

Are you including acceleration in your calculations Keith?

When you are at the top of the climb, the rider B, behind is still climbing with 10 seconds to go before that rider reaches summit.

Now you start accelerating down the mountain the rider B behind is still climbing.

Now rider B reaches the top of the mountain, you have moved away. You are 1 minute away.

Only when rider B starts to accelerate does the time and distance start to return to previous levels.

I agree with Keith that the time gap reports don’t seem credible. Time gaps should be reported just the way he says. Rider A reaches point X, then Rider B reaches point X. The time gap at that moment is the time elapsed between Rider A reaching that point X and Rider B reaching point X.

In Zwift the time gap reports seem to yoyo back and forth, maybe when changing from an incline to decline and vice versa. The proper time gap is  not the time it would take Rider B to reach rider A at rider B’s current speed, but it appears that that might be the way it’s being reported right now. 

If A and B are alike in every way, and riding at the same effort on the same equipment with no drafting, and there’s a 60 second gap amounting to 500 meters riding up a hill, when rider A has crested the hill and is riding downhill and is now 800 meters ahead, the time gap is still 60 seconds. B will pick up speed on the downhill and be at A’s present position 60 seconds later.

Watch bike races – the time gap is measured a fixed point on the road. A goes under the 10km to go banner and then B goes under the banner 30 seconds later. The time gap is 30 seconds. The distance between them is irrelevant; the time gap is simply how much sooner one rider crossed the fixed point before the other one.


Yes, I agree, if the race has a fixed marking point X. At fixed point X, all the variables have balanced, incline-decline.

But within the journey because of acceleration and deceleration the gap and so time difference, fluctuate and so that fluctuation is reported.


My wife and I can start a race together.  Lets say she gets to the KOM at 30 minutes. I get there at 30:10. we start the decent halfway down and she passes a point at 35:00 I then pass that same  point at 35:10 yet she is shown as a minute ahead. 

I concur that the time gaps are messed up - they actually seem to be more like distance gaps that are then converted to time based on your typical speed.

For example, when I’m on a flat section of road, a rider who is maybe 25 metres in front of me is shown as being 3-4 seconds ahead on the sidebar. If I try to count seconds between that rider passing a landmark and me passing it, it seems reasonably accurate, though occasionally slightly overestimated.

However, when I’m climbing somewhere steep like the Epic KOM for example, a rider that is 25 metres in front is still shown as only being 3-4 seconds ahead, even though because my speed is so much lower, it takes more like 12-15 seconds to reach the point that he was previously at.