Kickr accuracy problem solved (n=1 and I think?)

Triathlon Forum
1

I have been having accuracy problems with my kickr for quite a while.

I havn’t been able to verify it until recently, but I have been having some very successful workouts - producing power numbers that I have never seen before.

A few weeks ago my new power2max came. When I ran it on the kickr, I found that there was a very consistent difference of approx +12 watts.

I purchased a calibration kit and used it extremely carefully, but it made no difference.

I took it back to the LBS that sold it to me (and provided the data that demonstrated the difference). They told me that differences between powermeters is to be expected and there was nothing wrong with the kickr.

I was not able to let it go, and continued to work at it. Given the consistent difference, it was looking like an ‘offset’ issue (a ‘slope’ problem would produce varying differences - less at lower workloads and greater at higher workloads).

I did another calibration that I followed with a test ride. I did not do the spindown (as recommended following a calibration) - I noticed that the kickr read consistently with the p2m.

I did a spindown (10 minutes into the ride) - then kickr immediately read high (again about 12/13 watts).

It seemed like the spindown calculated an offset to add to the raw output from the kickr power meter to compensate for loss in the drivebelt etc. The calibration kit applies a known weight to the ‘sensor’ (the plate located next to the flywheel/brake mechanism) - it would allow adjustment of the forces at that point (ie. slope and offset), but would make no provision for the forces/drag imposed in the drive mechanism. Assuming that the ‘spindown’ routine adds an offset to account for these forces, it seemed reasonable to assume that the spindown was not correctly accounting for these forces.

Guided by a hint in another forum post, I looked at the drive belt - it was significantly below the recommended tension (approx 15-20mm of play). This would explain the strange noises the kickr has been making for quite a while.

I adjusted the belt as per the wahoo instruction video and did another calibration (followed by a test ride).

This time the kickr read approx 10 watts lower than the p2m before the spindown. After the spindown (at 6 minutes), it tracked well with the p2m.

I know that the second test was quite short, but it seems to show a clear change (hopefully a lasting improvement).

I have attached images of the pre and post belt adjust power comparisons. I have also attached an image of the original test ride, which showed the consistent 12 watt difference.

Notably, the spindown time reduced from 20 seconds to 11 seconds. It is also a lot louder now.

Hopefully this is helpful for someone.

kickr accuracy test - 6 dec 16.jpg
kickr accuracy test - 10 dec 16.jpg
kickr accuracy test - 10 dec 16 - post belt adjust.jpg

2

Now you can see why Wahoo has brought out a new version of the Kickr. Now if I could have had a constant 12 watts difference between my power meter and my Kickr Snap I would have been a very happy camper. For me the power was all over the place. After getting a replacement that was no better than the first with power accuracy I returned it for a refund.

3

Kickrs are not accurate to their own specs. They are junk.

4

I took it back to the LBS that sold it to me (and provided the data that demonstrated the difference). They told me that differences between powermeters is to be expected and there was nothing wrong with the kickr.

You need to find another bike shpp.

5

Just curios, did you try pairing your KICKR to your P2Max and use P2Max to control the KICKR? I know this doesn’t solve the KICKR power issue but at least your will have consistent power numbers from your P2Max.

6

I was aware of the option, but was hoping to find a better way - I have the problem of using multiple bikes (tt and road,race and old enough to leave in the bike storage at work) and only one crank based pm (and a couple of powertaps, that I have been finding increasingly annoying). Getting the kickr to work accurately seemed like the best solution (particularly given that the powermeter was one of the main reasons for buying the thing in the first place).

7

Is this first or second gen Kickr?

thanks

8

First generation - purchased mid this year.

9

Very good that you got it dialed in a bit.

I did not tamper with my belt out of fear of breaking it like I read a couple do. I ended up with just using the power meter control option and that has worked well enough for me. However, I was, like many, hoping the trainer wattage would have been halfway decent like Wahoo made claim. Mine was 20 watts off from my meters and that was not acceptable.

Thanks for sharing your experiences.

10

Latest update:

The belt broke, as predicted by Felt_Rider.

I did another spindown a week or so after adjusting it and the spindown had increased to 17sec. It broke shortly after. I think it that the reinforcing started to fail under the increased tension and it was only a matter of time until it broke.

I did another accuracy test shortly before it failed - it was within 2 watts of the p2m during steady work in ‘sim’ mode (wahoo app), but was running approximately 6 watts high during a climbing sim on the fullgaz app (the kickr file was also more chaotic than the p2m file).

I replaced the belt and did another accuracy test after about a week of use. Post spindown, it is now running a pretty steady 10 watts higher than the p2m - 10w at 150ish and 11w at 260ish (indicated by p2m).

I have made a simple spreadsheet that allows me to remove a ‘known offset’ by exporting raw data from golden cheetah and then re-importing the modified data back again. It should be good enough in the short term.

11

Kickrs are not accurate to their own specs. They are junk.

Some are, some aren’t. I generally run my P1 pedals for power and Kickr as a controllable trainer on Zwift as i don’t 100% trust the Kickr for power, but my Kickr is close enough to my P1 numbers.

12

I’ve done 3 tests w/ my Vector’s connected to my 820 and my Kickr connected to Zwift. Both have showed 1% different. I’ve had a friend tell me he did it on quarq w/ similar results.

I wonder why yours is so off

13

I really like my Gen I Kickr having owned a CT, and KK.

With that said I think the Gen I issues comes down to a low quality strain gauge and/or a gauge working in a small range being extrapolated. Sensors are often higher on the relative contribution of cost. This creates a temptation to shop for savings and think one can manage the hardware quality or lack there of with firmware. I would imagine there is a factory calibration and end of line testing to put the unit within spec (+/- “x”) using a calibrated ergometer. Hearing the issues and dealing with their tech support, there are variables such as temperature, light, friction, hardware, production…that impact calibration curve versus factory set. My experience is it is also non-linear which a simple offset will not address.

I have been using an PM to run and even with external control you can see that “driving” the Wahoo to set resistance is problematic, but likely due to another set of variables (communication latency, firmware (TR and Wahoo). It generally hangs close with PM control, but is subjective to spikes that can be challenged with short intervals. All the challenges to get it sorted are ok by me, but I am quite use to tinkering with stuff. However, in retrospect I would have gone a different route or waited until they got it sorted out. Sounds like Gen II is better, but still has some issues.

I don’t know all the new smart trainers, but the the old dinosaur of CT holds up pretty well with regards to accuracy. Cost competition isn’t always a good thing for the consumer.

14

I really like my Gen I Kickr having owned a CT, and KK.

With that said I think the Gen I issues comes down to a low quality strain gauge and/or a gauge working in a small range being extrapolated. Sensors are often higher on the relative contribution of cost. This creates a temptation to shop for savings and think one can manage the hardware quality or lack there of with firmware. I would imagine there is a factory calibration and end of line testing to put the unit within spec (+/- “x”) using a calibrated ergometer. Hearing the issues and dealing with their tech support, there are variables such as temperature, light, friction, hardware, production…that impact calibration curve versus factory set. My experience is it is also non-linear which a simple offset will not address.

I have been using an PM to run and even with external control you can see that “driving” the Wahoo to set resistance is problematic, but likely due to another set of variables (communication latency, firmware (TR and Wahoo). It generally hangs close with PM control, but is subjective to spikes that can be challenged with short intervals. All the challenges to get it sorted are ok by me, but I am quite use to tinkering with stuff. However, in retrospect I would have gone a different route or waited until they got it sorted out. Sounds like Gen II is better, but still has some issues.

I don’t know all the new smart trainers, but the the old dinosaur of CT holds up pretty well with regards to accuracy. Cost competition isn’t always a good thing for the consumer.

One usually gets what they pay for. And the newest kid on the block is not always the best for long term quality.

15

Given overall value, I wanted buy another CT despite it accuracy without significant feature additions.

16

If you talk to Wahoo, they are helpful with the difference in power.

I had about 10w off versus my P2M and Stages. They suggested an advanced spin down (and also gave beta firmware that uses the new generation power measurement instead of the strain gauge----but the advanced spin down fixed my power differences to within 1-2w at 350w.

My quarq is still aways 10-15w lower than my other meters and the KICKR, but thats another story.

Talk to them. The advanced spin down and even the beta are an option and really helped.

17

I have done every suggestion and than some from them, agree they are responsive but their resolutions do not work across the board. The latest beta did make a noticible change for the positive with power spikes and dips less frequent when married to PM, but there are many of us out here that will never have standalone accuracy as advertsised without hardware changes. I was fortunate to land a used P2M for low cost as I do not think I could live with the performance as a standalone even with recent refinements. Again, perhaps GenII is appreciably better.

I always thought that KK could do a really nice power controller with fluid dynamics via an aperture. I think in next couple of years this will all get nailed down as software is going 3rd party, a focused and accurate hardware solution should be forthcoming.

18

Kickrs are not accurate to their own specs. They are junk.

Absolutely, I had 2 kickers both crap…time to move on to Neo or back to good old computrainer… I’m surprised how well they suppress bad reviews comments and youtube videos, anyone that has “shitty kicker” on youtube doesn’t even show up in any searches, only fame and glory, internet became $hit some time ago…

19

Long time kickr user (over 2 yrs) with a history of power problems I just gave up on (spent time adjusting belt tension, broke and replaced belt and eventually gave up). As an Android only user, I was doubly annoyed that I can’t even setup my kickr to use my quarq’s for power, so I just ignore the kickr power in everything and only read quarq power but use the kickr to control resistance (which is kinda annoying but works). Wahoo’s story from way back when was not at all helpful, I’m glad to hear that they are more helpful now. Can you give some idea of what an “advanced spin down” was? I’m considering giving it yet another go at resolving based on your positive experience.

20

It’s a hidden calibration feature that is Accessed via the app. Different system. The new beta eliminates the strain guage and goes optical like the gen2 KICKR.