Spped not matching effort.

I understand the speed on my Garmin wont match the speed in the game.It doesn’t seem to match the effort I put in either. If someone passes me and I put out more power, there is no immediate response and some times I am peddling like made and my power is up as well as cadence but I am only going 5mph?

Hi James,

So, your wattage goes up but you speed stays the same? Can I ask what equipment your using (brand, make, and model) and how they’re paired?

Correct, I can pedal like mad but my speed will not change. At other my wattage is low but my speed is up. Seems like there is a 5 minute delay on the speed. Heart rate and cadence are instant though. I am using the Garmin Sped/Cadence sensor GSC10 and a Blackburn Mag 3 trainer. The cadence is paired as speed/cadence and the speed is paired with the classic trainer box. I also tried the newer speed sensor that mounts to the hub and no change.

I’ll second that… there are times that I am in my toughest gear pedaling like a hamster on a wheel but the watts are low and virtually no resistance.   There are times if I stop pedaling completely and restart the seems to some resistance but nothing like I fell it should be…   Hills don’t seem to be an issue most of the time the effort matches what is on the screen.  I’d say the flats are pretty much a waste of time.   Very frustrating and disappointing.    Any suggestions?

Getting the same problem, any answers. Kit is a TACX Vortex smart. The tacx app matches with a garmin sensor for speed but Zwift always puts it down to a very slow speed


Just set up with Tacx Vortex.

Having the same issues.

  1. Pedaling in my top gear as fast as possible, on the road i would be doing over 60kph. garmin shows 60 but Zwift showed 27kph.

  2. When other riders go past I still cant catch them at 63kpm, they just ride away.

So far this is not a very satisfying experience?

Can you help?

Hi Zwift team, I am having the same issue here. Using a MacBook Pro with Garmin cadence and speed sensors on an Tacx blue motion. Garmin ant+ usb2 dongle extended by cable pretty much lying beneath the bike.
If I use the Sufferfest app it works with the same setup.
Could this be a performance issue of the mac?

Same problem following


Same problem here, with the Tacx Vortex and a PC.  Watts drop when climbing even though on all out effort, also when sprinting, my times drop when I get on the bit and put out higher watts.  As well when I start a coffee ride, the pack is long gone before I can get my speed up, always playing catch-up but cannot ever get to the group.

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I have just purchased a new Tacx Vortex and having the same problem where the effort put in is not giving the speed in Zwift but is on Tacx and Garmin.


I am paying a subscription and thinking of stopping it unless you can help. Whats the problem?


Are you trying to compare the speed it is showing on the Tacx and Garmin to what is being shown in Zwift? If you are the speeds will very rarely if ever match. The Tacx and Garmin do not know about the virtual terrain within Zwift along with other variables. Wattage (which is real) is the main focus within Zwift, not speed (that is virtual).


Any chance of getting a clear answer on this please Zwift?
I’m having very similar problems on my Tacx Vortex. Gradient changes I pedal like hell and the rpm drops and eventually I will grind to a halt.

I even have a video of the issue.

David Ward - Inp moved on and started talking to Tacx. Turns out the Vortex is probably faulty and have sent it back to the retailer Tredz for (hopefully) a solution but currently stuck without a turbo.

David Ward - further info. I had to carry out an ftp check using the tacx utility app and tacx training app which showed the wattage and the speed were really low for the rpm ( getting on average about 70 Watts for about 113 rpm - speed although not relevant was showing about 14kph when I would have expected over 200watts and 27kph.

 At a lower level of effort (rpm) the resistaance was too high

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