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KICKR Core slipping feeling

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KICKR Core slipping feeling

Old 12-09-21, 07:34 PM
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pennpaul
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KICKR Core slipping feeling

I use a KICKR Core with Rouvy. On a ride yesterday there were some steep sections of about 13-14% where IRL I know it's going to be really hard for me. For the most part, it was, but towards the end of the ride, as I pushed down on the pedals, it felt like the KICKR was slipping, but only on every other downstroke. The route says it maxes out at 17% but those must be very brief. For several seconds the resistance felt much less with one leg than the other on the downstroke (don't remember which) as if something was slipping. As the gradient reduced to 10% and below, it felt more "real".

The Core can simulate up to 16%, and maybe with my weight, it reached its limit? I was still way below the max power, though. I saw some 6W/kg at times, and I was putting out some fantastic numbers towards the end. It seemed too good to be true.

I did update to the newest firmware last weekend and also ran a spindown. Is this because of the extra steep sections, or am I headed towards a warranty issue with my Core (8 months old)?

Thanks,
Paul
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Old 12-10-21, 02:22 PM
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I have a Kicker and have not experienced this. although i think this is a difficult thing to describe. i've monitored the USB traffic and i know that zwift is constantly updating the grade simulation to the Kicker. mine was not a Core but i expect them to be virtually identical. also mine was a 2017. i have a refurbished 2018 i just rode for the first time yesterday, it felt the same.
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Old 12-11-21, 07:52 AM
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I have no idea if it's the same thing, but I would describe the feeling I get from my kickr when the "slope" is very steep as "slipping." It's not a natural feeling, that's for sure.
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Old 12-13-21, 07:58 AM
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This sounds like a belt issue. My Core experiences no slippage-like feeling at all, even on the steepest slopes with my max wattage exceeding what the Core is rated for. I would contact Wahoo Support.
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Old 12-13-21, 08:36 AM
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i don't recall offhand but isn't the belt toothed? a slipping belt would feel very jarring and not likely to be only on the down-stroke of one crank. at least that is what i think.

to diagnose this i'd be inclined to use the wahoo phone app and set it for a specific target power and ride that for a bit. i'd expect the app to tell the core to target a specified power once and leave it there. this should be smooth. try a few target power levels.

with rouvy (and others) the grade is constantly changing so simulation commands are constantly being sent. although now having used rouvy once i think it is not so frequent. with zwift i'm pretty sure it is because i have monitored the usb traffic and can see lots of data being sent to the trainer.
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Old 12-13-21, 12:40 PM
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On my kickr, a slipping belt is definitely quite jarring. Almost as jarring as when it broke, or maybe more. I think the slipping feeling is just what a magnetic brake feels like under heavy load.
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Old 12-15-21, 12:05 PM
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Originally Posted by pennpaul View Post

The Core can simulate up to 16%, and maybe with my weight, it reached its limit? I was still way below the max power, though.
Quite possibly you exceeded the maximum incline for your weight. 16% max is I think for a 75 kg rider. So if you are any heavier than 75 kg then the effective max gradient reduces. Also your Kickr could well be power limited at low cadence. I'm not sure what minimum cadence is required to accurately simulate the 16% gradient. So basically if you are heavier than 75 kg and grinding away at a very low cadence then you are unlikely to get the full resistance of a simulated 16% incline.
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Old 12-15-21, 10:12 PM
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Originally Posted by spelger View Post
to diagnose this i'd be inclined to use the wahoo phone app and set it for a specific target power and ride that for a bit. i'd expect the app to tell the core to target a specified power once and leave it there. this should be smooth. try a few target power levels.
Good idea. I'll give this a try.
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Old 12-15-21, 10:18 PM
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Originally Posted by unterhausen View Post
On my kickr, a slipping belt is definitely quite jarring. Almost as jarring as when it broke, or maybe more. I think the slipping feeling is just what a magnetic brake feels like under heavy load.
Hmm...since it's magnetic and magnets perform worse in heat, I wonder if there's a correlation, but then I'd think Wahoo would have accounted for that.

It's definitely not jarring. That would make my heart (and wallet) sink if I experienced that.
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Old 12-16-21, 05:10 AM
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Originally Posted by spelger View Post
i don't recall offhand but isn't the belt toothed? a slipping belt would feel very jarring and not likely to be only on the down-stroke of one crank. at least that is what i think.

to diagnose this i'd be inclined to use the wahoo phone app and set it for a specific target power and ride that for a bit. i'd expect the app to tell the core to target a specified power once and leave it there. this should be smooth. try a few target power levels.

with rouvy (and others) the grade is constantly changing so simulation commands are constantly being sent. although now having used rouvy once i think it is not so frequent. with zwift i'm pretty sure it is because i have monitored the usb traffic and can see lots of data being sent to the trainer.
Yeah, Zwift is clearly sending data on a constant basis as my Kickr Bike responds dynamically to incline changes when riding on rolling terrain. Both in resistance and physical inclination. There is no obvious lag at all. I think where some Apps differ is in their transition between different gradients. For example Zwift seems to transition smoothly between gradients, which feels quite natural. But Bkool makes instant step changes from one gradient to another, which feels very harsh and one of the main reasons I stopped using it. Rouvy and Ful Gaz also seem quite smooth in their transition changes. To get the smooth transition I guess they must be sending multiple resistance commands to the trainer to create the ramp effect, while I guess Bkool is just sending out a single number with no regard to the transition. So if the gradient goes from 0 to 10% I guess it just goes from 0 and then straight to 10% while other apps send requests for say 0, 2, 4, 6, 8, 10% over the course of a few seconds.

I think your diagnostic idea is good. I would add that it's worth testing to see how it responds at low, medium and high cadence at the target power levels. Also compare low vs high gears. Low cadence, low gearing and high power is where trainers find their limitations. At some point you will hit a power ceiling at very low cadence and it will be nowhere near the quoted max trainer power. Especially in a low physical gear where the flywheel speed is relatively low.
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Old 03-04-22, 09:39 AM
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I was riding a route last weekend when I experienced this again. I was on a steady 4% climb when all of a sudden I felt the resistance drop, and then I see my power numbers jump more than 100W for the rest of the ride. I was already half way on the route and it was towards a Rouvy challenge so I kept going but someone observing would think I'm cheating.

I finally put in a ticket with Wahoo. They send you a link to troubleshoot the trainer step by step. At the end you ride in ERG mode for at least 5min at >100W with a cadence between 80-90rpm then export and email them the fit file. I also emailed them the fit file from my Rouvy ride.

Although I thought I ruled out all connection issues (I connect with BT from my laptop), Wahoo thinks it's still connection issues based on the fit files they analyzed. Maybe it was the easy answer for them, but I'll try their recommendation--get an ANT+ dongle.
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Old 03-04-22, 11:21 AM
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I use an ant dongle for all the trainer connectivity but did once try the BlueTooth connection once but i forget why. what would probably be more useful for them is to have a trace from the ant dongle in addition to the fit file. the fit file will only contain information that the app sees and records. you can try installing WireShark and capturing all data to/from the USB port with the ANT dongle in place. that will then have the data sent to and received by the application. you know, if the application is telling the trainer to ease up on the grade then the trainer will ease up on the grade. the trace will tell them that. i just had a look and it seems that WireShark now can capture BlueTooth data as well. you might want to capture that if that is how you are connecting now until you get the ANT dongle.

just an idea. i have the kicker and this does not happen to me. sorry to hear about it as i know stuff like this can be pretty frustrating.
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