fcriscuo

Hi,

I've been completing Zwift rides using a Wahoo Kickr Core for about 30 months. I use a Bluetooth connection between the trainer and an Apple iPad running the Zwift app. There is a wireless extender in the same room. Except for an occasional lost connection, I normally do not have any problems completing a Zwift ride or group event. The trainer's resistance corresponds to changes in the course's grade as expected. I recently began using some of Zwift's structured workouts and I've run into a problem where when the workout completes a high-intensity (i.e red) interval, the trainer doesn't lower its resistance to match the new interval's lower resistance. If anything, it becomes too hard to pedal. This only happens when the workout goes from very hard to a lower intensity. It does not happen when the workout goes down from moderate to easy. My Zwift setting for resistance is 100%. I use my iPhone to run the Zwift Companion app during these workouts. I mention this because one of Swift's FAQs suggests placing a phone into Airplane mode. I don't think that is the problem here because I use the same app during regular rides.


Thanks in advance for your suggestions. Ride On.


Fred

spelger

i think you need to isolate the problem, is it zwift or is is the connection or is it the kicker. likely not the connection. wahoo had a phone app that could control the kicker. you mikght see if that is still available and use that to control a training session. if it works then the problem is not the kicker. if it does not then maybe the zwift. i never really did any zwift workouts, only typical rides.

fcriscuo

Thanks for your reply. I found an item on a Wahoo support page (where I should have looked in the first place) that explained my problem. "This is known as an "ERG Mode Lockup" (or sometimes the "Spiral of Death") and is the most common cause for trainer lockups." As my cadence dropped, the trainer's resistance increased, putting me into a positive feedback loop until it locked up.

spelger

I've heard of this. Bad PID loop, should never happen with competent programming. Shame on wahoo for not fixing this in their FW updates.

and shame on zwift for not detecting this.

rm -rf

I don't use Zwift. But using the regular Kickr as a controllable trainer, I sometimes get very high resistance -- is this at very low candence? I'm not sure. I usually fix it by stopping pedaling for a few seconds, then it's resistance goes into a reasonable range.

From a google search:
In ERG mode, the trainer attempts to hold you at a target wattage, regardless of cadence or speed. If your cadence slows, the trainer to increases resistance to maintain the target power. Decreasing your cadence too much will force the trainer to apply more resistance than you can be pedal through. This is known as an "ERG Mode Lockup" (or sometimes the "Spiral of Death") and is the most common cause for trainer lockups.

EDIT -- ha, interesting: I'm using the Kickr App, in Erg Mode. I set the resistance to 100 watts in the app.

Start from zero cadence: it lets me slowly ramp up the cadence.
30 rpm, 40 rpm, steady pressure on the pedals, showing 60w, 80w...
to get to 70-80rpm: it needs some strong pedal force to rapidly increase cadence, showing around 200w for a few seconds. I didn't want to take 10 seconds or longer to easily increase cadence.
at 80 rpm or so, 103w, easy pedaling, I can raise it to 90+ rpm with little extra effort. This feels like 100w.

Slowing the cadence, with very light pedal pressures:
60 rpm, still reasonable to pedal, showing 86-99w depending on pedal pressure.
40 rpm, getting much harder to pedal.
30 rpm, hard but manageable, I can increase the cadence with a hard effort.
20-25 rpm: uh oh. Getting very hard to turn over the crank.
Within a second or two, it now shows 0 rpm, and I'm standing on the pedals with full body weight, and pulling on the bars. just barely turning it over. Must be 400-500w of effort. It shows 0 rpm, 17w. Ha, no.
Let it stop for a couple of seconds -- everything resets. I can start spinning up reasonably easy.