See if there's an email address on DC Rainmaker's blog. This kind of question is right up his alley.

Few things. Vector S is measuring one side of power. then extrapolating it to estimate total power. If you had a leg imbalance then you could see a greater difference in watts as depending on the effort.

Other thing: Kickr is measuring total power. If anything, Kickr tends to be the one that measures high. Your OP is not clear - did you do kickr spindown after warm-up? You should do this every ride 9-10 minutes into the ride. Vector 2S calibration can be at start.

Regardless, pick one PM to trust for FTP tests and training and stick with that one. All the major training software programs lets you use external PM to control the Kickr if you so choose.

Based on the numbers below it looks like your Kickr is reading 17% higher. I'd check it a few times over varying wattages and if the spread remains consistent then pick one and stick with it for all your workouts. If they don't remain a consistent spread then you've probably got something else going.

i did the spindown after 15 minutes of warmup, after that , another vector2s calibration . i dont know how to control de kickr with the vector , i use zwift and trainer road and so far i havent seen the option on both . Tnxs for your help

I have the Vectors and I've found that the readings vary all over the place until I get the torque to about 18-19 ft/lbs. From 20-30 ft-lbs it was stable. If you didn't use a torque wrench then you might want to give that a shot. 20-25 ft/lbs is really tight.

Yes but it should be consistent on the differences , how come when im at 140 watts the diference its only 15 watts, and then, when im not in erg mode ,doing the ftp test it jumps to 40 . thats my concern

tku

I will go to my LBS to do that ,and make sure that the torque is below 20 .

tku

283/243=1.165
140/120=1.167

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Eliot
blog thing - strava thing

Other way, tighten it to at least 25. Garmin recommends a torque spec of 25-30 lbf-ft (34-40 N-m), and I set mine there for the best reading.

I had just noticed that it is really all over the place until 18 for me, then going to 20+ made it read the same all the time. I followed their reqs though and set it to 25.

edited to get to at least the recommendation.

why would you torque them below spec ?

From Garmin

"Garmin recommends a torque spec of 25-30 lbf-ft (34-40 N-m). The Vector's accuracy can be affected when under-torquing pedals."

edit : Sperris posted the comment above mine as I was typing. I think we are saying the same thing

I've seen the same thing... I have the 1st generation Vector pedals, fully updated with latest firmware. The readings are pretty flat (as in not too erratic) however they are consistently about 50 watts low compared to various computrainers I've been on. The power readings are extremely consistent from day to day so I really don't worry about it much. Removing/re-installing, changing the mounting torque doesn't help and so far neither have Garmin support reps... My conclusion I that Garmin has/had serious quality control issues with the manufacturability of the strain gauges which has a large impact on accuracy.

Interesting, My Vectors have been within 2% of my Computrainer and Quarq.

The only time I would get erratic numbers was the first ride after install. If I reset the angles after the first ride they would fall back into place.

I wonder what they would read if you put a known weight on them.

Crank length is properly set ?

Crank length is definitely a good one to check. As well as the far-more important torque on it (yes, even Vector2).

That said, one thing to keep in mind is that since you were doing an FTP test, you might realistically be looking at leg imbalances. For example, for me, once above FTP for any period of time, or in sprints, I start to diverge whatever evenness I had. It's part of the challenge with any left-only solution. For example, Best Bike Split has recently been trying to tackle some of the challenges they're starting to see in predictions due to the variances they see in left-only data.

17% is a lot, but if you start to add-up other facts, it may not be unheard of. First though, double check the crank length (and ensure there isn't a scale factor listed in there either), and again, the torque. In general, it's actually tough to torque too hard on Vector. Under-torque is your enemy...

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My tiny little slice of the internets: dcrainmaker.com

do they still support a scale factor ? I thought they removed this.

If they do support it it may be a way to get things to line up or at least get closer.

It should still be there, though now to think of it - maybe it doesn't show for VectorS (definitely Vector full). There were some issues with it also not showing on non-Garmin products (i.e. bePRO/P1).

Now, the thing is it's actually not for what people think it's for. It's not designed to 'even out' left-only imbalances. But rather, to account for crank length variance. So if you have 172.5's on your left leg, yet 175's on your right, you can use scale factor to 'fix' one of the two. Super confusing, yes. But super-useful to the small portion of the population who have different crank arm lengths.

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My tiny little slice of the internets: dcrainmaker.com

I was thinking of using it to make your Vectors line up with your computrainer. So if your Vectors are reading 3% lower than the CT, adjust the the scale factor to make them line up. I was thinking for the double sided version which is the one i use.

I never saw the scale factor in the 510 or 920 menus and I did look for it. That's why I thought they removed it.

It's in the 510, but I believe you have to be actively connected to the Vector pods to see the settings. Don't have either Vector or an Edge 510 handy, but I know it was added to it. I don't believe off-hand the 910XT has support for it though.

A smarter person than I would have to think hard about the maths involved, as I'd assume crank length starts to dive into cadence (RPM value) discussions using the torque values, so a straight 3% increase might not work. But again, too much thinking for me at the moment. Hopefully the OP can just correct the issue a normal way.

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My tiny little slice of the internets: dcrainmaker.com

Your KICKR is most likely over reporting your power... Wahoo acknowledges this problem. I have 2 KICKRS and both read significantly high compared to my SRM.

Look at MULTIPLE threads on this subject.

I got a kickr recently and it reads 15% higher than my SRMs, rather than 3% lower like my computrainer does.

Kickrs are shite - steer clear.

@donzo98 - have you a link to this acknowledgement or any documentation - this would help me greatly in returning my unitt

+1
I would consider looking at the Kickr before looking at the power meter considering that there are a lot of us that have had that problem. Mine was about 15+ watts off (high) from my Quarq.
I am now using the power meter control option in TrainerRoad and PerfPro and I am very happy. It will not graph as smooth as it may appear by using the Kickr's power, but at the end of the workout you can trust what you upload into TP, WKO, GC or whatever you use to keep track of your training data since it is using your power meter to control the resistance.

Here is a fairly good review and comparison between the Kickr and SRM power meter.
http://bikeboard.cc/wahoo-kickr-ber5640

As Donzo mentioned that Wahoo acknowledged it (reluctantly I think), but I bet they were getting a whole lot of calls, emails and web based gripes that they finally addressed it with a firmware update that allowed the user to enter their power meter sensor data, but PerfPro and TrainerRoad actually came to the rescue first by writing in this option into their applications. Unless one happens to be the rare lucky with a Kickr that is within a few watts and has a power meter, I would use the power meter control option in the application. If you use the Wahoo app you will have to do a firmware update and enter the PM sensor into the Wahoo app.

Best wishes

I don't think you will have much trouble returning should you want to...

I decided to keep mine... and like Felt Rider, I use my external PM (SRM) to control it now. I thought about getting a TACX Neo, but after reading the reviews and issues others are having I will stick with the KICKR.

With the SRM control... it is now doing what I want it to.

Thanks - although this would require me buying an iPad though as Android app does not allow external PM to control it (I am told).

I'm not sinking more money after bad though. Back to the computrainer

If you are using Perf Pro or Trainer Road you don't need an Ipad.

I have a laptop in the basement which I leave down there to run Perf Pro. Are you going to use any 3rd party apps to run it?

I was planning on using them, but I wanted the option of hoping on and just doing a session without the hassle of booting up a computer.

The Kickr is not what I thought it would be at all.