Major difference in power between Wahoo Kickr and Garmin Vectors - please help!

I found it much easier to access the advanced spindown on the Kickr when it was connected via bluetooth. Using a Samsung Galaxy 5 phone.

There should be some difference between power at your rear hub and power at your pedals, correct? The difference between the two is your drive train (in)efficiency…

But that shouldn’t be too big. Unless you need to replace your crank bearings.

Hi everyone,

Thanks so much for your responses. I really appreciate it.

I’ve tried to perform a factory spindown but it looks like Wahoo have updated their iOS app and tapping the screen 5 times doesn’t work anymore unfortunately. I’ve reached out to them (again!) so will see what they have to say.

As for the drive train, it’s a pretty new bike with few miles on the clock so don’t think it will be that but good to know for future.

I’m really beginning to think I should have opted for the Tacx Neo instead!

I would not rule out the Vectors. If you have a friend that has a turbo w/pwr as well as a bike w/pwr where his numbers are reasonably close (i.e., 3%), I suggest you test your bike on his trainer. It would be even better if he/she also had a Kickr.

Why do you insist on wanting to use the kickr for power if you have a stand-alone power meter?!? Is it just because of the artificially smoother power lines? Or because it gives you better numbers?

If you just use powermatch and all your troubles are sorted!!

My kickr snap reads roughly 20w higher than my stages but it doesn’t matter as I only use the stages power, Inside and out!

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Not the case at all. Powermatch adds another variable in the loop between TR, Wahoo and Erg. That communication has its flaws and it let me down. I will never us Powermatch for a ramp test again

Power meters and Erg don’t always play nice with each other. Knowing the offset between the 2 power sources can be useful so you don’t have to “hope” powermatch works. At some power levels the two sources (Kickr and Quarq) are spot on and other power levels they drift apart. Also, cadence and gearing (inertia) tends to affect how PM tracks with the Kickr. Below is my experience today playing with cadences matching my Kickr Snap to my Quarq;

Then when I keep my cadence 100+ the entire workout my Kickr Snap and Quarq are nearly identical:

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Im not sure if its just me but I have noticed this issue since starting of April (the new update affected a few kickrs). For some reason, the anaerobic workouts were bloody difficult and I couldnt finish any of my workouts.

Did a threshold workout today and the kickr under reads by 36 watts (18%) on average in the space of a 10 minute interval.

Ive been switching back and forth between powermatch and just a kickr source alone and the workouts are much much easier if I use just the kickr as a source.

Did an advanced factory spindown once and I calibrate the trainer at least twice a week. Could it be that its a software issue?

FYI I also have a vector 2 and a kickr 2014. Maybe you and I have the same issue. I am contemplating buying a torque wrench to ensure that the garmins are torqued properly. its too many variables to determine whats going wrong.

Hi @Muzzaffar Frankly if you have vector 2’s you need a torque wrench and must torque to spec. It makes a great difference. I moved to V3s when my V2s started to develop play in the pedal spindle and still torque them up. Get one, and use it for torquing all those other bolts up on the bike to spec. You will not regret it.

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Hi @benmeaker I have a kickr core and vector 3 pedals. With my previous vector 2 pedals and the Elite Direto the power showed pretty much the same between them. (But the elite direto was awful).

Since swapping to a kickr core and getting vector 3 (under warranty - spindle wear), I found that the kickr was under reading by around 20-25W consistently across the range. I was using a wahoo elemt to look at the kickr and a garmin 920 to look at the vector 3s. I used powermatch to mattch teh Tr power to the V3s. However the difference was annoying. Like you I did checks, recalibrated the kickr both ways, I checked my drive train (just in case - and found my road bike BB was worn, but that changed little) and kept recalibrating the V3s.

I contacted wahoo. The finally said there was a firmware upgrade available under beta I could try. To be frank, I did not because I did not want to screw up a session.

Recently the difference seems to have closed a bit, but it varies. Sometimes it is almost bang on. Other times there is a 10-15 W difference. The thing that puzzles me is that it is not a percentage difference (as you might expect with a 5% drive train loss). It seems to be consistently the same difference lower (subject to the usual power fluctuations you get). Both my devices are on 3 second average.

I don’t have an answer, except reply on the pedals, use power match and look at the Trainer Road screen, not the reading from the kickr. and keep recalibrating, and doing any firmware updates.

Frankly the workouts with powermatch and my FTP seem fine (read that as “As hard as I woudl expect”).

When I had my Vector 1’s I had trouble with Power consistency until I finally bought a torque wrench to properly torque them to 40nm as prescribed by Garmin. The problem with the vectors is that once you ride them they kind of ‘settle’ in and change the torque. Ideally you torque them to 40nm then ride them and do a couple of sprints and retorque. Then repeats 2-3 Times until you get consistent Power readings.

Even with my Vector 3’s I torque them up, then calibrate them twice. I always get a smaller reading on the second calibration.

Frankly the torque helps set the strain so if you are not torquing them consistently…

Also check out how grease on the threads affects torque settings in various engineering sites. (the grease means the threads slip more easily so the applied torque is actually greater than you intended). https://www.engineeringtoolbox.com/torque-lubrication-effects-d_1693.html so you may need to reduce the torque by up to 40-50%!!

Garmin are ambiguous on this.

So either clean the threads really well, or consistent use a small amount of grease and adjust accordingly.

Hi @PhilSJones. Appreciate the feedback. I have just ordered a torque wrench. Wanted to go all fancy with a park tools 6.2 but didnt agree on the pricing. Ended up ordering from an auto shop for 1/4 of the price.

That would explain why my workouts are incredibly hard after travelling with my bike (hence the removal and installation of the pedals). Will check back on the forum after torquing them properly. I hope it at least eliminates one variable as to why the power readings are so far apart.

Wise move. The one thing I found is that my small range torque wrench only works one way. (You can’t torque up a left hand thread except by reversing the wrench). So you have to do one pedal from the outside and the other from the inside the frame… or pedal crank… the effect of which is that, in effect, despite the left right thread difference, you end up turning the torque wrench the same way on both sides (but from a different place because the wrench is also reversed). That might not make immediate sense - but it will :slight_smile:

The other thing is the claw spanner and the angle of the claw vs the angle of the torque wrench - in other words you can have the claw spanner pointing ahead of the wrench or at 90 degrees to it. Does that make a difference? Does it change the point at which the force is applied and therefore the effective torque? The engineer in me worried about this, but in reality the answer is effectively, a bit, but no, not a lot. https://www.finishing.com/118/94_crows_foot_torque.shtml But just be consistent.

If you have a power meter, there is no valid reason not to use powermatch unless you don’t ever use your PM on the road. There is also a bit of skill/practice to making it work properly. No sudden changes in cadence, if its not matching just give it a second to catch up etc.

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If you have a power meter, there is no valid reason not to use powermatch unless you don’t ever use your PM on the road. There is also a bit of skill/practice to making it work properly. No sudden changes in cadence, if its not matching just give it a second to catch up etc.

Not everyone has that experience with Powermatch. Also, not everyone has the same priorities. I haven’t used Powermatch for, hmm, maybe a year, and I gather it’s probably improved over that time. I haven’t bothered trying it again though, because:

(a) I had issues with it, tried all sorts, was never perfect.
(b) I have a Neo. I’ve recently had cause to doubt my Favero pedals (they’ve since been repaired under warranty). I trust my Neo to be more consistent, more than I trust my pedals.
(c ) Outdoors, my apparent FTP is a chunk (maybe 20W) higher than indoors. That’s not unusual, c’est la vie, etc. etc. But that means that my indoor FTP does not translate directly to what I can do outside anyway.

So Powermatch doesn’t add anything useful for me now. And it has a (maybe small nowadays, I don’t know) risk of buggering up a workout and annoying me.

I think those are valid reasons. You are free to disagree though! :slight_smile:

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It would be surprising if a bolt-in torque difference would create a large power reading difference - the installation torque is meant to ensure a secure installation as well as no damage to the pedal, but would not change the strain gage readings unless the pedal was so loose as to move around.

This said, you are measuring one parameter (power) with two instruments (Vector powermeter + trainer); the two instruments give you two different measures. You have a few possibilities:

  • You trust one of the instruments, and ignore the other one (that’s the cheap and simple, and clearly in this case you would trust a powermeter over a trainer)
  • You use a third instrument to arbitrate - meaning you find a friend who has a trusted power measuring instrument - be it a powermeter + trainer combo that lines up well, a bike with a crankset or hub powermeter, etc - and test your pedals on that setup.

DCR wrote an interesting piece a few months ago on the general topic of “I don’t know if my powermeter is correct”, I suggest you refer to it.

Not surprising at all. Even Garmin recommends a specific torque and states that it will affect the accuracy of the power data. This is a well known “issue” with the Vectors prior to the latest Vector 3 which has/had its own issues. You must torque to spec and calibrate properly or the values will be all over the place.

https://support.garmin.com/en-IN/?faq=5Gw1QIkylj1IcFx5AYEGS8

Ha! Seems like the 2016 model is riddled with problems, even though Wahoo refuse to acknowledge that. I’ll do as you say because it seems that the Kickr will never provide accurate power readings, no matter what I do.

I’ve torqued the Vectors numerous times and still have this discrepancy between them and the Kickr unfortunately.

Great shout. A mate of mine has a pair of the new Vector 3s so will give those a shot and see if the same issue arises. I have a feeling I’ll still see that ~12% difference…