How do you control your speed?

I have Garmin Vector 2 power meter with a Garmin heart rate monitor. I ride on a Cylceops Jet Fluid trainer. These connect to a PC via ANT+.  Zwift will not allow me to pair my speed sensor unless I drop the power meter.  Zwift correctly shows my power and heart rate (matches what I see on my Garmin 510 head unit)

Once riding my speed is not controllable.  I can drop to below 50 watts and my speed stays for minutes constant.  I can push my watts over 600 and see a 1 to 2 mph boost.  My Garmin headunit registers significant changes in speed from my speed sensor.

this makes it impossible to set a pace and actually ride with someone within the app.

the speed in Zwfit is power based.  Pairing the speed sensor therefore has no effect.  I ride with others by matching W/kg.

Speed within Zwift is determined by your watts, your weight, the in-game bike chosen, in-game drafting and elevation changes.

Can you upload a couple of screen-shots David?

David. If you have a powermeter - in this instance Vector2 then use this as the sole requirement for speed. Zwift will do the rest. Just make sure your weight is correct in the settings!

I’d also set the powermeter to 3sec smoothing in Zwift profile settings.

So, ditch the gamin speed & cadence sensor. I’ve moved my speed sensor to my outdoor wheels. Pair the vectors to Zwift power and cadence.

Vectors are ANT+ so you’ll need to connect via dongle.

I had already done what was suggested, using only the power meter via ANT+ dongle.  I can go from 200 watts to 600 watts and my speed is static.  I can then go to <50 watts and my speed remains constant.  The only thing that changes it is elevation.  Giving up on Zwift


Speed on Zwift is meaning less, your concern should be on watts over time. Remember you are sitting on a trainer not moving. 

Paul, I agree with that for training purposes.  But since I cannot control my speed within the app I cannot participate in group rides or the events offered on Zwift.

nit being funny David but listen to the advice. You don’t work on Zpeed in Zwift you work in w/kg. I ride with my friend all the time and his trainer gives totally different speeds to mine and he is 100kg compared to my 73kg but we both ride at an agreed w/kg and stay together just fine. 

Speed is irrelevant, it took me awhile to understand this as well. 


As long as your watts are correct then you should have no issue doing group rides or races. Again, Zwift is mostly about watts per kilogram.

David. If you’re definitely ONLY paired to Zwift via the Vectors then it’s probably an issue with the Vectors.

Speed when using a powermeter is a calculation based on W/kg I.e. power and the weight you set in your profile, and the terrain you’re on. It’s tied together, one simply won’t fluctuate wildly when the other is constant.

Vector 2’s are known for being random number generators if the torque is wrong. If you have a large smoothing value this may keep the power smooth but fluctuate the speed. Depends on whether Zwift works off the smoothed power or absolute per/s value. Don’t think it would matter.

Take off the smoothing value totally and look at the absolute power values. At a constant effort in may fluctuate by +/- 20W but not really more. 

Make sure all other sensors are removed from wheels / cranks etc to take them out of the equation.


Stephen,  Vectors are paired with the Zwift PC app and my Garmin head unit.  Power values are identical on both.  They are set to 3sec smoothing and have minimal fluctuation (< 5 watt).  Torque values were verified during installation. I have calibrated the pedals against a CompuTrainer trainer and that matched within 2 watts.

As stated I have sustained a 600+ watt sprint (it earned me the achievement within Zwift) and this had almost no impact on my speed (speed raised less than 2 mph).

I still don’t see a reason why you can’t do group rides and/or races. The speed will not jump up the way it does in real life, this is the same for EVERY rider within Zwift, not just you.

Steve, your comment was helpful.  Thank you.  I believe I understand how the app is working now (at least on flats).  Have to mull over how changes in elevation can be counter-balanced.

Extraordinarily frustrating.  Have not been able to stay on anyone’s wheel more than a few seconds.  Either passing them or dropping back.

No problem. I’d do a bit of testing on your own with a Zwift workout that has stepped power intervals where you hold the same power for a few mins+. Do it on a flat course and look at the speed. Shouldn’t vary much within the interval. Try it with and without power smoothing. At least have something Zwift support can look at if you’re still having issues.

I noticed moving from virtual power to a powermeter was a bit of an adjustment. I’m still on a normal fluid trainer, and I know that using a smart trainer is even more different, especially on hills where it’s instinctual to put out more power with a smart trainer. You don’t get the same ‘feel’ on a dumb trainer, so I normally up a couple of gears on hills. Same effect. Lower cadence, higher power.