Acceleration bug

I’ve seen the acceleration bug (where a rider starts doing speeds up to 100km/h with normal power numbers) a couple of times in big group events but I’ve never experienced it myself.

I decided to do a BRT crit race at Richmond this morning and joined 5 minutes before the start. I selected the C cat but Zwift put me in the D cat, oh well, I’ll just take it easy then I thought. The race starts so I accelerate up to speed and then settle into a nice comfy 180w. Then I notice I’m in front of everyone else and no-one is passing me. I check my speed and I’m doing 60km/h with only 150 watts and the speed keeps going up.

I briefly consider seeing how fast I can go but figure it would be better to try fix the issue so I stop pedaling hoping that a quick stop and go would be the fix but when I start pedaling again the bug is still there. I quit the event and do a free ride in Watopia (I am on iOS which allows you to select a new ride without restarting the app) and the bug is still there. It’s only when I completely close the app and restart it that the bug goes away.

I believe this is a known issue with Zwift and I’ve sent them a support ticket about it already. Just thought I’d post this in case you ever find yourself flying along at 60+ km/h on the flat.

Hi @Umi_Sonada
I witnessed someone speeding along like this recently. It’s something we need to investigate further before we elevate this “known bug” status.

For those reading along: you can help us figure out what happened by emailing us at and sending two things:

  1. Your FIT file from that session. This is how to download the .fit file
  2. The game log files on the computer you use to Zwift. Instructions to locate them log files are here.

Thanks for your help, everyone!

EDIT: Please also mention the high speed bug and specifically ask for Shuji when you email the Support team.

I’m pretty sure I’ve seen someone post about this issue on this forum before and that they had contacted support about it.

The first time I saw this was when Yorkshire was released in one of the official group rides where someone was blasting around doing 100km/h.

Support responded to my initial contact but they seem to have failed to understand the issue and told me to update the firmware on my power meter. The power meter is not the problem. This is a Zwift program problem.

Anyway, I sent them the fit file and log file.

Here is the fit file loaded into Strava if anyone wants to see exactly what is happening.

(equal 2nd time on the first strava segment lol).

Near dead flat Richmond road. Speed starts at 48km/h at 180 watts and increases to 66km/h and I’m doing less than 50 watts (by this time I had figured out something was very wrong and had reduced my wattage). There was no drafting involved as I was doing 60km/h and riding away from everyone else.


Thanks for emailing your files to our Support team. Your case has been assigned to me, and I’ll send this to the right team for investigation.

This issue’s been upgraded to a known bug so we can start working through it.

Thanks for sending your files; they are very helpful.

Hello, same issue here. iOS (Apple TV, companion on iPhone) running tacx neo2.
At first I was wondering what was in my Christmas Pud when I hit 345kmh, 3 days later still doing the same thing.
I will try to find files to email though.

Ride on, we’ll ride on x10, as I normally cruise at 34.5

1 Like

Hi all I got an issue today. I changed my bike from TT to an “normal” one and I had draft benefits, but I got so much, that I rode up to the front with 100km/h and more without any cadence oder power. After a while the group catches me and after a while the same issue appears. After I had it more than 5 times, I decided to change the event, but the same happened in the next three events. Now I’m frustrated and need help. I’m using an iPad, an iPhone and a Elite Direto powermeter. Many thanks for any hint upfront. Uli

Welcome to Zwift Forums. It sounds like you’re reporting something similar to our other iOS users, so i merged your question into this discussion.

We’re aware of this bug and and working on it. Thanks all for your patience.


Unfortunately I had this too, joined a ride and suddenly I was way out front up to a speed of 75 mph. Everytime I came off the specific exercise it would constantly be the same as before. So frustrated that I had to completely switch off zwift and wahoo for a day or two.


My wife had this issue two days ago. I rode straight after her and initially had no issue then it started…

Hello all,

I was affected by the same issue yesterday. I participated the 1st TDZ 2020 Stage in LONDON while speeding up to <100km/h.
Since I wanted to have this stage completed I finished this stage and resulted 1st place of course.
I am not sure if ZWIFT will delete my results but it was was not my fault and I want to have at least have the stage marked as completed.
After London I started another session in NYC (and the same issue occured.

I am using Android Version of Zwift, so looks like it’s not just an IOS topic.

Iill try today or tomorrow and hopefully this issue will not appear again…

This bug must be why some segments have been ridden at 88 km/h.

After 4 attempts could not transfer to races today. I was left on nYC course, all riders disappeared and despite clicking “join event” zwift would not transfer me over to the start line. My name did appear with other racers in event at side but that was it.

I tried again later and this time got in, but once we started, I flew away from everyone very quickly. I finally noticed my speed was well over 80 mph at 4.0 w/kg and I quit the race.

Anyone else have this problem? Solutions?

Welcome to Zwift forums. I merged your question into a thread already in progress. This is a known issue that we’re addressing. We apologize for a jarring and confusing experience.

FYI I was pointed at this issue after logging a different issue in the forum. Is it now accepted as a bug or are you still looking for occurrences. I did a ride yesterday at 1.7 w/kg and did 117 miles in 90 minutes. Would be happy to provide any data I can. It was on an AppleTV so don’t know that I can access files on the device but I do sync automatically to TrainingPeaks so I can get whatever file was posted there if necessary.

@chris_halioris This is a known issue that we’re still working on. We are able to reproduce the conditions, so we do not need to ask for your log files. Thanks everyone for your patience

I am having this issue too. Started with Yorkshire warmup then went Bologna for a C race. It started wierd there as it just let me free ride from pen. So I join D cat and it put me in the pen on a trainer. I then switched back to C cat and I thought all was fine. However at the start I sped up to 220 kph. The climb was fine but then when I kept riding to get my training for the night I
just kept flying.
How do I fix this? I just got updated right before this ride.

Have the same yesterday.
After crit race, i have switched off and on again zwift and try to start regular workout, but bug was still there. Have to run other app to do a training :frowning: