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kickr core power accuracy
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Hi All, and HNY

Have a core from April 2020 which is running latest firmware. Noticing that during sprints it's reporting my power is 80-100 watts lower than what my pedals are showing. I have Assioma dual sided which are calibrated but also match my mates Powertaps dual pretty well

Normal riding is a lot better - around 5-10 watts lower sometimes, but I can take that given drivechain losses.

Have perform numerous spindowns using the terrible utility app on Android and also on Zwift, but still the same

Anyone else noticed this and have any tips for a fix or at least closer readings?


Many thanks
Last edited by: chatlow: Jan 10, 21 3:55
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Re: kickr core power accuracy [chatlow] [ In reply to ]
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Are you sure that you have the latest firmware? Ray says the last update fixed his.

https://www.dcrainmaker.com/2020/12/wahoo-releases-accuracy-fix-for-kickr-v5-2020-test-results.html


If yours is not fixed by that, contact Wahoo.
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Re: kickr core power accuracy [ThomD] [ In reply to ]
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ThomD wrote:
Are you sure that you have the latest firmware? Ray says the last update fixed his.

https://www.dcrainmaker.com/2020/12/wahoo-releases-accuracy-fix-for-kickr-v5-2020-test-results.html


If yours is not fixed by that, contact Wahoo.

Yeah did see both this and gplamas videos but thats when the core would overshoot by 100w or more during sprints. My issue is the other way around and under reporting.
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Re: kickr core power accuracy [chatlow] [ In reply to ]
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I got a core this last Nov. accuracy was good for many workouts usually within 1.5% of my SRM (which reads slightly under my powertap). The day I decided to join a tour de zwift ride the kickr started reading 10% low which made keeping up on the ride more difficult than it should have been. Not sure what caused the sudden change but did numerous spin downs without any improvement.

So far the only response I’ve gotten from the support ticket I opened was a canned email about powermeters in general not matching.

At this point I’m sceptical about the claimed accuracy. I suspect most people don’t compare power for every ride and wouldn’t necessarily notice a change. It would be good if there was some objective way to check the torque measurement used but I haven’t heard of one.
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Re: kickr core power accuracy [chatlow] [ In reply to ]
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Have you tried the factory spin down? It’s like the regular spin down on EPO. I haven't done one myself, but I did recently become aware of this. It does seem likely to be worth a shot first.
Last edited by: weiwentg: Jan 10, 21 5:35
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Re: kickr core power accuracy [ThomD] [ In reply to ]
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ThomD wrote:
Are you sure that you have the latest firmware? Ray says the last update fixed his.

https://www.dcrainmaker.com/2020/12/wahoo-releases-accuracy-fix-for-kickr-v5-2020-test-results.html


If yours is not fixed by that, contact Wahoo.

Is that update not for the Kickr, not the Kickr Core? I checked my Wahoo app, and it says that my Core's firmware is up to date.
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Re: kickr core power accuracy [weiwentg] [ In reply to ]
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Oops. I missed that. We own two wahoo trainers and I still can't keep their product line (and generational differences) straight.
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Re: kickr core power accuracy [ In reply to ]
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For my Core, I'm seeing the exact thing this firmware would fix. If I'm under maybe 17mph on Zwift at a power under 150w, it over-reports versus my Quarq. As soon as power and speed go up, it's much more in line with reality.

Overall with my Core, I'm have the issue of it reading higher than my Quarq. Which is backwards. A trainer should read less than the meter upstream given the % drivetrain loss. Meaning, either the Quarq or the Core are off by more the % drivetrain loss!

I've done a spin down. May try the factory spin down thing.

I'm also going to fill a thin plastic bag with a known amount of water and read the torque in the Quarq app just to see what I get. I don't think you can zero or tare off of that, but at least I would "know".
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Re: kickr core power accuracy [burnthesheep] [ In reply to ]
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thanks for the replies, interesting to see I'm not the only one.

few things; yup, tried a factory spin down once. Although there are articles suggesting you shouldn't unless advised by Wahoo because 'it can damage' the trainer, but all fine afterwards, didn't make a difference to be honest.

still seeing a constant 10-15 watts lower than pedals, way more more during a sprint.

It's got me thinking if I should try calibrating when cold perhaps? Is it likely to boost the numbers up to match?
Last few spindowns have been after at least 30 mins of use when the unit is pretty warm. I know Wahoo suggests calibrating after 10 mins of use.
Also does it make any difference using the wahoo app for a spin down, the wahoo utility app (pretty terrible, but spindown works) and / or Zwift?

I know the power discrepancy I'm showing prob sounds petty to most, but it does make a difference, especially when racing on Zwift, which I love. If I'm going to use pedals for power, then I could have got away with buying a cheaper smart trainer

Happy training, all
Last edited by: chatlow: Jan 13, 21 23:03
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Re: kickr core power accuracy [chatlow] [ In reply to ]
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My brand new kickr core is spot on imo, roughly 2-4% lower than my garmin vector 2s pedals. You'd expect a pedal power meter to overread most during a max sprint I would of thought, as so much strain will be going through them. (I'd of thought, someone will soon tell me if I'm wrong). Also, dual record with your power meter, but use your turbo for your zwift power if racing, its viewed as better practice for a number of reasons, and having lower watts on zwift makes the extra few watts on the road seem all the more. I'll attach my most recent dual recording data for comparison.
Last edited by: TommyBTri: Jan 14, 21 0:44
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Re: kickr core power accuracy [chatlow] [ In reply to ]
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Powermeters can be funny.

My Kick Core (2018 model) consistently reads 10W lower than my Vector3, while these in fact read 5, sometimes more watts lower than 2 other PMs I have tested against, which both have been consistent at least between each other.

So if in Zwift, I use my PM readings :)

----------------------------
Need more W/CdA.
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Re: kickr core power accuracy [mrlobber] [ In reply to ]
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My Kikr snap which is a wheel on trainer has always read 10-15% low compared to the Quarq power meters I have on my Tri bike and one of my road bikes. So the low reading issue may go beyond just the KICKR core line. Calibration never seems to change anything for me.

I mainly used the trainer power for zwift over Bluetooth while I simultaneously used my quarq over ant + with trainerroad. I don't race on zwift so its not the biggest issue. It did annoy me though so I ended up using a second ant+ dongle so I could use my Quarqs for Trainerroad and Zwift at the same time.
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Re: kickr core power accuracy [j.shanney] [ In reply to ]
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Why not just use the “Control w/ANT+ Power Meter” function in the Wahoo app or the power matching function in Zwift? That way you are using the “true” power reading in your opinion to control your KICKR Core.
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Re: kickr core power accuracy [burnthesheep] [ In reply to ]
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burnthesheep wrote:
For my Core, I'm seeing the exact thing this firmware would fix. If I'm under maybe 17mph on Zwift at a power under 150w, it over-reports versus my Quarq. As soon as power and speed go up, it's much more in line with reality.

Overall with my Core, I'm have the issue of it reading higher than my Quarq. Which is backwards. A trainer should read less than the meter upstream given the % drivetrain loss. Meaning, either the Quarq or the Core are off by more the % drivetrain loss!

I've done a spin down. May try the factory spin down thing.

I'm also going to fill a thin plastic bag with a known amount of water and read the torque in the Quarq app just to see what I get. I don't think you can zero or tare off of that, but at least I would "know".

I actually have the same issue. Comparing the results to a Sufferfest 4DP test, I think the Quarq was reporting 2-4% lower power than the Core. That was true at a bunch of power durations (5s, 1min, 5 min, 20 min). On a different bike with a Pioneer single side PM, the discrepancy was a bit larger, I think averaging 7%. I'm taking that as confirming that the Core is probably reading a bit high, rather than my Quarq reading low.

I think that one person on the Zwiftpower forum may have expressed the same issue. DC Rainmaker's review of the Core seemed to say that the Core was reading high in sprints, but about the same in longer durations. If I read him correctly, anyway.
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Re: kickr core power accuracy [weiwentg] [ In reply to ]
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weiwentg wrote:
burnthesheep wrote:
For my Core, I'm seeing the exact thing this firmware would fix. If I'm under maybe 17mph on Zwift at a power under 150w, it over-reports versus my Quarq. As soon as power and speed go up, it's much more in line with reality.

Overall with my Core, I'm have the issue of it reading higher than my Quarq. Which is backwards. A trainer should read less than the meter upstream given the % drivetrain loss. Meaning, either the Quarq or the Core are off by more the % drivetrain loss!

I've done a spin down. May try the factory spin down thing.

I'm also going to fill a thin plastic bag with a known amount of water and read the torque in the Quarq app just to see what I get. I don't think you can zero or tare off of that, but at least I would "know".

I actually have the same issue. Comparing the results to a Sufferfest 4DP test, I think the Quarq was reporting 2-4% lower power than the Core. That was true at a bunch of power durations (5s, 1min, 5 min, 20 min). On a different bike with a Pioneer single side PM, the discrepancy was a bit larger, I think averaging 7%. I'm taking that as confirming that the Core is probably reading a bit high, rather than my Quarq reading low.

I think that one person on the Zwiftpower forum may have expressed the same issue. DC Rainmaker's review of the Core seemed to say that the Core was reading high in sprints, but about the same in longer durations. If I read him correctly, anyway.

My best real world data point is full TT kit 40k at 25.6mph on 252w AP with time soft pedal stop sign right turns each lap. With the Quarq. Seems pretty legit.

Maybe I’ll take the power on Core as OK as an inflation for what extra I can do with outside airflow cooling.
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Re: kickr core power accuracy [TommyBTri] [ In reply to ]
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TommyBTri wrote:
My brand new kickr core is spot on imo, roughly 2-4% lower than my garmin vector 2s pedals. You'd expect a pedal power meter to overread most during a max sprint I would of thought, as so much strain will be going through them. (I'd of thought, someone will soon tell me if I'm wrong). Also, dual record with your power meter, but use your turbo for your zwift power if racing, its viewed as better practice for a number of reasons, and having lower watts on zwift makes the extra few watts on the road seem all the more. I'll attach my most recent dual recording data for comparison.

Hi, is that comparison using Zwift power? I looked into that the other day, because it would be handy to produce a graph from my numbers, for free. Is there a way to convert my garmin tcx (from pedals) to.fit file if the distance is 0? Not using a speed meter for head unit, it just records power, HR and cadence.

thanks

Still curious whether calibrating at colder temp might up the watts to a more accurate level in line with my PM. Will try this soon
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Re: kickr core power accuracy [chatlow] [ In reply to ]
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yeah, just go into analysis and pick the zwift activity and then in the comparison bit upload the fit file into it, I use strava files after my garmin has uploaded to it which I then delete off strava after there on zwiftpower.
Last edited by: TommyBTri: Jan 21, 21 1:00
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Re: kickr core power accuracy [TommyBTri] [ In reply to ]
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joined TDZ ride this morning. Literally a 2 min warm up then into a calibration through Zwift when it was still cold. Don't know if this is 'bad' for the unit but the number seemed a bit more inline with my PM. Will test again tomorrow.
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Re: kickr core power accuracy [chatlow] [ In reply to ]
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chatlow wrote:
joined TDZ ride this morning. Literally a 2 min warm up then into a calibration through Zwift when it was still cold. Don't know if this is 'bad' for the unit but the number seemed a bit more inline with my PM. Will test again tomorrow.

Do you happen to know if smart trainers like the Core/Kickr (direct drive) should read lower or higher on a cold spindown?

I've always done a spindown right when jumping on the thing as Zwift recognizes the devices on that screen.
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Re: kickr core power accuracy [burnthesheep] [ In reply to ]
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burnthesheep wrote:
chatlow wrote:
joined TDZ ride this morning. Literally a 2 min warm up then into a calibration through Zwift when it was still cold. Don't know if this is 'bad' for the unit but the number seemed a bit more inline with my PM. Will test again tomorrow.


Do you happen to know if smart trainers like the Core/Kickr (direct drive) should read lower or higher on a cold spindown?

I've always done a spindown right when jumping on the thing as Zwift recognizes the devices on that screen.


That's what I'm trying to find out. First time calibrating when colder and overall watts seemed much closer to that of my pedals
Last edited by: chatlow: Jan 21, 21 6:09
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Re: kickr core power accuracy [chatlow] [ In reply to ]
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chatlow wrote:
burnthesheep wrote:
chatlow wrote:
joined TDZ ride this morning. Literally a 2 min warm up then into a calibration through Zwift when it was still cold. Don't know if this is 'bad' for the unit but the number seemed a bit more inline with my PM. Will test again tomorrow.


Do you happen to know if smart trainers like the Core/Kickr (direct drive) should read lower or higher on a cold spindown?

I've always done a spindown right when jumping on the thing as Zwift recognizes the devices on that screen.


That's what I'm trying to find out. First time calibrating when colder and overall watts seemed much closer to that of my pedals

Come to think of it, when I compared it to my Quarq I think I had already ridden for a bit so it was warm. That's when the Core read higher. More recently it has "felt" tougher on the Core and I had done a spin down on the Core when cold more recently.

I should go back and compare it again.
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Re: kickr core power accuracy [burnthesheep] [ In reply to ]
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Over a 3 hour ride on Wednesday....my Kickr Core and P2Max showed a 4 watt discrepancy on 230watt AP.
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Re: kickr core power accuracy [burnthesheep] [ In reply to ]
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burnthesheep wrote:
...
My best real world data point is full TT kit 40k at 25.6mph on 252w AP with time soft pedal stop sign right turns each lap. With the Quarq. Seems pretty legit.

Maybe I’ll take the power on Core as OK as an inflation for what extra I can do with outside airflow cooling.

I suspect most people just use their smart trainer as the power source. If this problem is systematic across the Kickr Core, then it's sort of a level playing field, at least among Kickr Core users. Only thing I can think of is to do the spin down protocol consistently, keep checking for firmware updates. I'd better do another dual recording versus the Quarq soon, and if the discrepancy is widening, I'll consider a factory spindown.
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Re: kickr core power accuracy [weiwentg] [ In reply to ]
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I did 2 dual recordings with my Kicker Core recently with a fresh from SRM PM7 upgrade to a Cannondale crank. The first was an easy Zwift ride and the crank over read the kicker by about 5-10% at first, but closed the gap as time went on. The second was a zwift tt race for about 25 minutes, after the trainer was warmed up on for a goof half hour. The kicker over read slightly in the 1 minute and under and under read slightly for the longer duration. It seems pretty spot on once its up to temp.
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Re: kickr core power accuracy [ridenfish39] [ In reply to ]
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ridenfish39 wrote:
I did 2 dual recordings with my Kicker Core recently with a fresh from SRM PM7 upgrade to a Cannondale crank. The first was an easy Zwift ride and the crank over read the kicker by about 5-10% at first, but closed the gap as time went on. The second was a zwift tt race for about 25 minutes, after the trainer was warmed up on for a goof half hour. The kicker over read slightly in the 1 minute and under and under read slightly for the longer duration. It seems pretty spot on once its up to temp.

Yeah, I feel this was my error. Following the spindown procedure well.

I also found my Quarq had gotten its first low battery. I tried using it instead for a workout and it kept dropping cadence and thus power, causing the death spiral. So, replaced battery and that seemed to improve.

That side of the house is also a bit warm and I'm literally in a bifold door closet with my setup with a fan, so.......there's that.
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