Kickr Snap feeling resistance changes in erg mode at set watts

I have few workouts that have 20min intervals at FTP. Even though the Kickr says I am doing a constant 240 watts it is much easier going uphilland  feels well under 240w and downhill feels much harder than 240w. On a recent workout in ERG at 220w for 60 mins my average HR up the mountain was 131bpm and down average HR was 161bpm showing just how much harder the resistance is. My workouts are using zwift to control the Kickr via ANT dongle. Have tried spin advanced spin down different tire pressures moving dongle next to the unit but still the same. Has anyone else had this or know of solution?

Yes, with the Kickr first gen doing a Zwift workout. Macbook with ANC+ dongle picking up the Kickr. I was getting a lot of ‘More Power!’, and ‘Less power!’ messages and with 20-40 watt jumps in reported power but I swear my cadence and pedal pressure were hardly changing. I just ignore the messages and I pass the workout stages. This is AFTER the new Kickr firmware updates for this year. I checked a workout I did BEFORE I did the firmware update and my power graph was much smoother  I don’t recall getting so many prompts from Zwift. If I use Wahoo app in ERG mode (not on Zwift) I can produce a very straight power line.

Marc, I have a Kickr Snap as well and I am experiencing the exact same thing as you. I notice a BIG difference in resistance in ERG mode based on whether I am going uphill (its easier to turn pedals) or going downhill (it gets harder to turn the pedals).

Glad I am not the only one. I have tried it connected to my pc and also tired with the ios app. the only way I mange to get it to work without resistance changes is to set the trainer as power source not the fec option, no controlable trainer paired. I then start the workout and control the watts manually using the wahoo app. A pain but a work around. I will submit a ticket now and see what I get back.

I did another steady watts Zwift workout with my Kickr 1st generation, with which I have done the latest firmware update and Advanced Spindown. It is connected to my Macbook Po with a Garmin ANT agent and dongle. I managed to keep power smooth and can only think that the Kickr/Ziwft communication is affected by outside environomental factors, like the fan, or the wireless modem. So Zwift loses dat and thinks power has dropped. I experienced a big power spike yesterday which stopped me pedally for about 2 seconds. It’s interesting that at power transitions between intervals Zwift takes a few seconds to adjust to my change in power, and there’s a technique to it. It’s best not to chase what Zwift is saying, because of the lag.  I know the Kickr is virtually perfectly smooth when I do erg mode with the Wahoo app with IOS. I can only think that it is a network issue here in Sydney Australia, where I have pretty indifferent data connection.

I have the same problem on my Tacx Bushido and reported it to Zwift in November. They blamed the trainer and said nobody else has reported the problem.

I get it over both ANT+ and BLE. According to Zwift logs I get a lot of drops over ANT+ but BLE is rock solid so I don’t think it’s interference related. It does seem a bit better over BLE but I think it’s a placebo.

My guess is that even in ERG mode Zwift still sends course gradient data to the trainer which confuses it.

Hi Kyle, it is good to know that it is not problem with just one brand of trainer. One way to test is to see if you experience fewer drops on a very flat course (Richmond) compared to a hilly one (Watopia Volcano). If you get more drops in the hilly course, that suggests the drops might be correlated with gradient data. 

Adam, I think you have a different problem to me, Marc, and Dylan. We all seem to have the same problem where riding uphill in ERG is easier than riding downhill. It’s very obvious when it happens and obviously would not manifest on a flat course.

What you seem to be reporting is just the general inaccuracy of target watts in ERG mode which from what I understand is to be expected to varying extents on all trainers.

I think you are right. Keep posting your experience with the problem!

 

I have the xact same problem, and I’m running the newer version of Wahoo Kickr Power. However, I don’t think the problem is with the trainers, as it is the Zwift software that is aware of the uphills and downhills. For some reason zwift is telling the trainer to increase resistance on downhill, and decrease on uphill. It is as if trainer control code is still aware of the environment, and then above that it’s another layer of code that is trying to counter the effects of the environment in ERG mode, and those two pieces of code is not tweaked the same, (or exakt opposite) . No one else is mentioning it, but I’m running with the setting; Trainer Difficulty set to Max

My issues with the Kickr are resolved after updating the trainer software. I have very smooth resistance changes in both ERG and normal modes, running Bluetooth connections. I haven’t noticed the problems mentioned above.

I found this issue went away again with my Bushido. When I still had the issue I noticed that it only happened at higher watts so it may actually be related to tyre slippage. It does seem like we all have wheel on trainers.

I have multiple ANT+ dongles so can sniff the ANT+ network and didn’t notice Zwift sending anything out of the ordinary (though there is a lot of “useless” ANT+ traffic and the trainers could be interpreting that noise as gradient changes).

The two most unusual things that I noticed and confirmed with Zwift support are:

  • Target watts in game is always rounded to the nearest 5W. So if the game displays a target of 200W it might have sent anywhere from 197-202W to your trainer.

  • Downhill gradients are always 50% of what is displayed in game. That means that with trainer difficulty set to 100% then a +5% uphill will actually be +5% but a -5% downhill will only be -2.5%.

I still have the same issue as I had in March. I feel the resistance lessen when going uphill in ERG mode and feel the resistance increase when I go downhill. Even in recovery intervals at 150 watts I feel the resistance increase when going downhill. If I’m doing a workout with vo2max intervals I always make sure to do those intervals on the flat or uphill, because trying to do a vo2max in ERG mode going downhill is simply too hard and will lead me to bonk and skip the interval. There are quite a few people reporting this issue, this is simply not “in our heads”, this is a real, observable feeling that the trainer is putting out and it would be nice to get a solution to this problem so I can do ERG mode workouts in zwift and not have to worry about whether I am going uphill or downhill and how that is affecting my effort.

I see this has gone silent for quite awhile but I too have the same problem of slightly less resistance going up hill and more going down on my first gen Kickr. It is showing the correct target power in workout mode but you can feel the difference and I can see my heart rate change slightly up or down depending on effort. Any more updates? Anyone else have this problem? The more people that have the issue then Zwift will need to look into it. 

I started this thread way back in March. I am on an Elte Drivo now and it does the same thing. I will raise a new ticket and see what happens.

With some experimenting I have found setting the trainer difficulty to OFF when doing a workout minimizes this to almost undetectable. I might be able to feel a slight difference when going up or down a hill but it may be in my head. I also pick the flattest courses to do a workout. Do not pick courses with hills or mountain. I put the trainer difficulty back up when doing a normal or group ride. The trainer difficulty can be changed on the fly during a ride when using a PC. 

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