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

Hi there TR folks,

I’m hoping you might be able to shed some light on some increasingly frustrating issues I’m having with my Wahoo Kickr (2016 model) and Garmin Vector 2 pedals.

The main issue is this: the Kickr registers roughly 12% higher power than my Garmin Vector pedals. That’s a huge $%^&ing difference. Unfortunately, it’s not even a constant difference. At times (and usually at lower power output), the difference drops as low as 6-7%. In others, it can be as high as 15%.

I’ve done everything you could possibly think of in terms of troubleshooting: recalibration, changing batteries, spindowns, etc. I’m tempted to kick the damn things as it may yield a better result! Anyway, I know you can power match on TR which is great but I’m still trying to figure out how on Earth there can be such a staggering difference between the two power meters.

I like to use ERG mode (who doesn’t it!?) which means it makes sense to set the Kickr as my default power source. However–and this is my BIG concern–when it comes to riding outside, be in for a training ride or in a race, my FTP/power zones won’t be applicable with the Garmin Vector pedals (i.e. I simply can’t set my zones to say 12% lower as there is simply way too much fluctuation).

I would really appreciate if anyone has encountered similar issues with their equipment and how to overcome these quite frankly pain-in-the-ass problems. Needless to say that I’ve contacted both Garmin and Wahoo about this issue and both parties have been utterly useless at helping me sort this out. So I’m hoping one of you fine folk might be able to help!

Cheers!

1 Like

This is why you would use Powermatch. The Vectors become the source of your power. TR adjusts the resistance of the Kickr based on the power from the Vectors. As a result, your indoor power and outdoor power are both from the Vectors and thus both consistent and meaningful.

As for your 12% diff… That is indeed huge. This could be the Kickr, the Vectors, or both. Is the Kickr running the latest firmware? Have you done an Advanced Spindown to set the brake strength? I do not know enough about the Vectors to be helpful. I have only read that they can be “fussy”. Torqued properly?

6 Likes

I went through this exact thing with a Kickr 17. Prior to getting the Garmin Pedals, I was over 4 watts/kilo, something to make me feel real good. I went back and forth with garmin support, I did a static calibration on the pedals, got new battery doors, and still a wide difference between my pedals and my kickr. I returned the pedals, and got some Assiomas. Same large power difference, made me suspect the kickr. I did a factory spindown on the kickr, and afterwards, there was a fairly close match between the pedals and the kickr. Unfortunately , my FTP went from 302 to 182

1 Like

I have a Kickr 2017 and before using PowerMatch was having trouble getting it to agree with Stages crank power meter. Here is what I did:

  • warm up Kickr for 10 minutes
  • do a spindown
  • do an advanced spin down
  • test and confirm it was now within 3-5 watts of Stages

Instructions for both normal and advanced spindown are here:

The advanced spindown is hidden, to access it you have to tap 5 times on a certain area of the screen in the Wahoo app.

2 Likes

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!

4 Likes

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:

2 Likes

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.

1 Like

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.

1 Like

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:

2 Likes

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.