"Just Ride" - Should my speed be at least *somewhat* proportional to my power?

(Bill Slobotski) #1

Ive read a lot of posts about Zwift’s speed being off by a few MPH or so.  I could live with that.  I have a Wahoo KICKR that is all paired up.  I choose what I believe is called “just ride”.  I start up in England on a mostly flat hill and start at 200 watts.  Zwift gives me a speed of 14 mph.  I then crank my power to 400 watts, yet Zwift still gives me 14 mph.  Is this the way it is supposed to work?  There is no large incline on this part of the map.

(Jon Mayfield) #2

Yes, your watts will start to accelerate you and 400w will certainly accelerate you faster than 200w over time.  It could have been the incline changed from 1% to 2% as you ramped up the power and thus the speed didn’t change dramatically.   This is more true if you’re a heavier rider.

Check your speed at 200w on a 0% gradient (shown at the top right) and see what it settles in at on your next ride.  

(Bill Slobotski) #3

Thanks Jon.  I was wondering if perhaps you guys have timers/filters in your algorithms that would require someone to apply 400 watts for a long-ish period of time before seeing results on the screen.  The test I described in my original post came after a pretty heavy 30 minute training ride and I was only able to hold 400 watts for 10 sec or so.  And I am heavier, 225 lb.

(Jon Mayfield) #4

10 seconds at 400w would slowly accelerate you beyond 200w, but it does take time to accelerate mass.   There’s no filtering on our side, but just like in an automobile applying gas doesn’t instantly make the car go 60mph, it simply starts the acceleration process.

Give Zwift a bit more time and I think you’ll see it acts similar to real life.

(Bill Slobotski) #5

Thanks Jon!  This is my first week of Zwift and am learning bit by bit. 

(Chris Renner) #6


make sure you have the updated firmware for your Kickr.  Go to your Wahoo app for this.  Then run the advanced spindown.  Make sure that your tire pressure is hard and consistent.  Increased wattage on flat ground should translate to acceleration.  There is a bigger learning curve for Zwift and trainer than you might think.  Little by little it will get better and better.

(Bill Slobotski) #7

Hi Chris,

I did an advanced spindown with my Android phone (using the Wahoo app) about a month ago.  I bought a new Ipad last weekend for Zwift, but oddly enough could not locate the Wahoo app in the Apple store.  I am guessing that the spindown data is stored in the Kickr, and thus my Android spindown of a month ago was adequate for running Zwift on an Ipad.  If I am mistaken please let me know!


(Chris Renner) #8

Hi Bill,

Harder, faster pedaling on the flat should increase wattage and speed almost immediately.

I am new to Zwift and trainers in the last three months and there is a significant learning curve to endure before all the pieces consistently fall into place.  I have a KickrSnap and only use my iphone to run Zwift.  I have had problems with erratic resistance, disconnected heart rate monitor, and most recently shrinking wattage output while I have been busting my butt up hills.  My heart rate at full tilt was higher than my wattage!  However, little by little I have solved all these problems and finally seem to have consistent performance that is pretty realistic. I connect by Bluetooth to the trainer and hrm.  I run a lightning wire from my phone to the tv.

First, make sure that you have the most recent version of Kickr firmware.  I have copied below from another thread on how to do this.

Second, at least for the Snap, it is recommended to run the regular Spindown before every ride.  This is to recalibrate your resistance based on your current bike/trainer conditions, such as tire pressure, oil temp, etc.  The Advanced Spindown is only supposed to run once.  My system seems to be working well, and in the Wahoo app, the ERG Mode Speed Simulation is On and the Erg mode power smoothing is On.

The below instructions were for the Kickr Snap, but I suspect  hold for the Kickr.

  1. Open the Wahoo Fitness app.
  2. Click the sensors icon on the bottom left side of the app.
  3. Click On the device if it is saved, find a new sensor if it is not saved.
  4. Click on the Wahoo device when it appears and wait for it to connect.
  5. Click the grey device icon with the Bluetooth emblem in it 10 times to bring you to the firmware update screen.
  6. Click on the 2.2.51 firmware (or newest)
  7. Once complete, go back to the sensors page,save sensor to the proper profiles.
  8. Inflate your rear tire before every ride to 110psi (or max trainer tire pressure)
  9. Tighten the roller so it barely touches the rear tire, then tighten it by 2 full turns
  10. Do a standard spindown and if the time is greater than 15 seconds please tighten the roller by 1/4 turn
  11. Do a standard spindown and if the time less than 10 seconds please loosen the roller by 1/4 turn
  12. Repeat steps 3 and 4 until you have a standard spindown within 10 to 15 seconds
  13. Do 1 and only 1 advanced spindown to lock the calibration in. Do not do another advanced spindown unless instructed.

If this doesn’t work, open up tickets with Wahoo and Zwift.  They are pretty good with response.


(Bill Slobotski) #9

Thanks for the detailed effort you provided, Chris!

In reading other people having similar speed issues, I have to believe that the Wahoo Kickr is not sending speed data in its Bluetooth packets, or it is sending them but Zwift is ignoring them and doing some sort of velocity calculation.  I found that going between 100 watts pedaling slow and 500 watts pedaling fast on a flat didnt affect my speed.