Control smart trainer's resistance with external power meter - important for Workout Mode

(Eric Oshlo) #141

While this would be a very nice feature for occasional use, I may be the oddball here in that I prefer doing structured workouts without ERG mode on Zwift. To me doing so has the following advantages:

  1. I can get actual workout power data directly from my Quarq power meter by pairing it as the Zwift power source and thus don’t fret about differences between my Quarq and Kickr.

  2. I can adjust the Kickr resistance to be simulating a steady hill climb, flat route or whatever the structured workout needs.

  3. It’s much closer to doing a structured workout IRL. When outside, there’s no device holding power for you regardless of cadence, etc. You have to do it yourself.

  4. When doing a high intensity interval, if my cadence drops very briefly to shift around grab a bottle, stand on a cliimbing workout, etc. the Kickr doesn’t virtually lock up on me trying to hold wattage at a very low cadence as it often does in ERG mode.

  5. Zwift still provides detail on workout segments, length, target power, indication on whether you are in the target range or not, time remaining on the interval, etc.

(Michael Gonzales) #142

Eric, all great points… and I actually agree.  But, I still want to be able to use my power meter across all rides and workouts.  That’s why I bought a power meter in the first place, so I could have relevant power info for indoor and outdoor.  Zwift just threw a wrinkle in my plans since I never thought about Zwift until last week!

(Michael Gonzales) #143

Hey Eric, just re-read your post… I think we are on the same page.  Are you saying you can pair your power meter while using a smart trainer, just not in ERG mode?  I’m not interested in ERG mode for training sessions… I’m interested in using my power meter while on a smart trainer (Tacx Vortex Smart).  So far I haven’t been able to use my power meter with the Vortex trainer… am I missing something here?

(Eric Oshlo) #144

Michael, yes you absolutely can use your power meter for all Zwift power data. I use my Quarq power meter for all my Zwift rides - free riding and structured workouts. In Zwift, I pair my Quarq (not my Kickr smart trainer) as the power source(upper left on the pairing screen) & cadence source and then my Kickr as the Controllable Trainer (lower right). 

This then keeps all my Zwift power readings consistent with my IRL (outside) workouts/rides while still allowing Zwift to control the trainer resistance for grade changes in non workout Zwift rides and via a manual setting in the iOS app for Zwift workouts.

The key issue in this thread is that folks would like Zwift to be able to control the trainer in ERG mode (hold preset power level regardless of cadence changes, etc. vs preset resistance level) in Workouts when pairing a power meter & smart trainer in this fashion. Zwift cannot do that at the moment. My note above was to highlight some advantages I see in not using ERG mode in Zwift workouts.

(Michael Gonzales) #145

Ahhhhh, I’m only a couple of rides into my Zwift experience, so I’ll cop to my newbie status on this one.  Feeling a little dumb…  

So you are really using your smart trainer as a dumb trainer while paired to a power meter?  Don’t now why I didn’t think of just pairing to my power meter!

Though, I do still think ERG mode should allow your choice of power meter or smart trainer… just not as pressing to me as training with power meter without ERG mode.  Still want to give the TR / Zwift dual mode a try too.

thanks to all for the help!

(Peter Schindler MGCC) #146

When you are on erg mode (whether controlled by zwift or any other system) you won’t feel the simulated hills etc. Your trainer will simply adjust resistance to get you to target watts.

However, you can still cycle around the virtual world.

When you use Trainer Road or Xert as an overlay, then you have erg mode set by trainer road or xert, and you can measure power based on your proper power meter, and have resistance controlled by the trainer but with resistance varying based on target power numbers as measured by the proper power meter.

(Eric Oshlo) #147

No, I wouldn’t say I’m using my smart trainer as a dumb trainer. I’m just not using it as the source of power data. I use my Quarq for power data.

My smart trainer is still paired to and controlled by Zwift to automatically change resistance to simulate grade changes (climbs/descents) when just riding the courses and also to be able to change the trainer resistance manually via the iOS app or keyboard to simulate steady climbs, flat TT, etc. when doing a Zwift workout. True “dumb trainers” such as a most fluid trainers, etc. are not capable of making those types of resistance changes

(Michael Gonzales) #148

Got it… I’m confusing ERG mode with the resistance control based on terrain.  Didn’t have to worry about that in TR.  Thanks again!

(Sunil Savkar WBR (C)) #149

RIght.  So to summarize:

(1)  If you are in normal free ride mode in Zwift, you can always pair a power meter with Zwift so long as it talks BLE or ANT+ (assuming you have the dongle).


(2)  If you have a KICKR or KICKR Snap, you can also as a work around in ERG mode for workouts use the power meter as well, by setting up the KICKR/SNAP to read the power meter using the ANT+ ID thru the Wahoo Fitness app.

(3)  What you cannot do and what I would still love to see eventually, is direct read of a power meter from Zwift which is then used to control whatever trainer you are on for resistance.  For some reason that combo seems to be a problem - believe they once implemented it, but something didn’t work right so they are still trying to perfect.

Anyway, even with KICKR directly reading from my power meter, I sometimes have to fidget around a bit to get things to sync up.  For instance, last night while doing a training program, I noticed initially the KICKR was reporting a different wattage than what my Garmin was showing for my P1s pedals, but once I actually modified the % level of work out up and then back down, oddly that seemed to cause the KICKR to fall in line. Oh well, was no big deal…

(Michael Gonzales) #150

now I’m confused again… has to be free ride to use power meter and smart trainer?  I’m going to stop thinking about this until I get home and set it up to see what’s what.


(Sunil Savkar WBR (C)) #151

Um, sorry about that.  In (3) above, that really just refers to directly setting up the power meter to work with Zwift WHEN IN ERG MODE while training.  Sorry about that and the confusion.

Again, in free ride mode, you always can set Zwift to read your power meter, and if you have a KICKR you can always use the solution in (2) to have your power meter (if transmitting ANT+) read through the KICKR itself which works with Zwift.

(Greg Hilton ARCC) #152

Or do what I have done and “tune” the Kickr to match your PM :slight_smile:

I did 3 x 3 mins with Zwift workout and ERG mode holding 270w, the P1 pedals (recorded separately on my Garmin) reported each interval as 270, 271, 276

All I did was follow the instructions in this thread, post 111

(Sunil Savkar WBR (C)) #153

Why go through that when you can now have the KICKR use your P1 pedals as a power meter source rather than its own system?  With that KICKR actually uses the P1 Pedals and Zwift then gets the same reading.

You can do this by going into your Wahoo Fitness app, going to the page for settings and enter the ANT+ ID of your pedals.  This will then allow KICKR to work with your pedals as the power meter.

You can test it out with the Wahoo Fitness app itself which will show you either a red or a green little symbol next to the KICKR when you are riding so you can see if it is properly reading from the pedals - u usually have to pedal a little bit for that to work.

Then quit out of the app, and you are all set.  Zwift will read from the KICKR which is reading directly from your pedals.

(Greg Hilton ARCC) #154

Sunil, that hadn’t been suggested when I did what I did a fair few months ago! Do you have to keep the phone on and working during everytime you workout or is it a one off setting?

(Sunil Savkar WBR (C)) #155

Sorry, just saw your query.  So you should be able to set it up with the Wahoo App, but then be able to quit out of it and just use Zwift normally.  That is what the person who noted it to me told me, and it seems to basically work.


Sometimes I still notice drift/difference in #s between what my garmin and zwift report, but they are far closer and I think it may do with the smoothing calcs that differ between both.  Otherwise I do think I am reading from the pedals.


So no, you don’t need to keep the phone on and working in Wahoo Fitness app for that.  In fact that would not work because then the Wahoo app would take over control of the KICKR which you do not want to have happen.

(Michael Henasey) #156

The suggestion to use the “Control w/ANT+ Power Meter” from the Wahoo Fitness App does not appear to actually work when I tested it.

After putting in the ANT+ ID of my Stages power meter for my KICKR in the Saved Sensors section of the Wahoo Fitness App on my iPhone 7, I started a workout from the Wahoo Fitness App and did notice a new icon next to the KICKR icon. I circled it in the screenshot below:

So I proceeded to test this by putting the KICKR in ERG mode and 100 watts. Then with another device (my iPad), I used the StagesPower app to connect to my Stages power meter thru Bluetooth. The StagesPower app was not reporting the same power as the Wahoo Fitness app. 

I then started up Zwift and went to the pairing screen. I clicked on Search for a power source and watched the power being reported by both the KICKR and the Stages power meter. They did not match.

The “Control w/ANT+ Power Meter” feature doesn’t seem to actually work.


(Michael Henasey) #157

Oh, and earlier this month I noticed some screenshots from Eric Min that were posted on his Strava workouts that had a ERGCorrect overlay. It looks like this is in the works finally…

(Sunil Savkar WBR (C)) #158

It is finicky.  I have had times it doesn’t seem to work properly, takes some playing with to get it to take.

Frankly I am not using Zwift much at the moment, rather using Trainer Road and there i can use my pedals separately with the trainer and though there is lag between the power reading and a response from the training, it is not bad.  Not sure why Zwift can’t get to where Trainer Road has been for a couple years.

(Eric C. (Zwift HQ)) #159

Hi Sunil,

This is not publicly available yet so I’m not sure how it’s finicky for you?

(Michael Henasey) #160

I re-tried the “Control w/ANT+ Power Meter” feature from the Wahoo Fitness App and this time it’s working for me!


I opened a ticket with Wahoo and they gave me the details on how to set it up properly. The setup is exactly as has been described online. I believe the key is to make sure you start a workout from the App first as this seems to put the KICKR into this special “Control w/ANT+ Power Meter” mode. After that, you can stop the workout and exit the App and the KICKR will now be controlled by your external power meter.


I tried Zwift after turning on “Control w/ANT+ Power Meter” and both workouts and free rides continued to work as expected and the KICKR continued to appear to be controlled by my Stages power meter.


Something I observed is that once you are in this “Control w/ANT+ Power Meter” mode, it seems to stick for some time. Maybe indefinitely? I reset the KICKR by clearing out my ANT+ ID and turned off the “Control w/ANT+ Power Meter” feature off and then started another workout in the App. After I did this, the KICKR wasn’t being controlled by my Stages power meter and the power readings from both had their usual discrepancy. Perhaps even a power cycle of the KICKR would reset it but I didn’t test that.


When the “Control w/ANT+ Power Meter” feature is on, the power being reported by the KICKR does not match my Stages power meter exactly but the numbers are much closer than when the feature is turned off. It seems reliable enough for me to continue to test and use though. There is a lag of a few seconds for the KICKR to adjust the resistance when you alter your cadence/effort/gearing/etc. TrainerRoad has a 10-second delay for their automatic calculation. I couldn’t tell how much there was with the KICKR.


I hope that Zwift’s “ERG Correct” feature allows both an automatic calculation and a manual offset, just like TrainerRoad does.