Not sure what you're asking, but:

1. Our Kickr's have tracked within about 2% of my SRM and my Quarq.
2. 300 watts on the flats feels different than 300 watts up a climb. With that said, the Kickr is "more realistic" than a fluid trainer.

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Right... what I'm asking is if you did an FTP test on the kickr, would you rely on those power zones in a race on the road? Or would you also perform a road FTP test? Sorry... new to using power so don't know the ins and outs quite yet.

Two things would potentially prevent me from using Kickr FTP numbers.

1. I've seen Kickrs that differed greatly in reported wattage. I do not believe they are as precise as an upper tier bike-based powermeter. It is also important to appropriately "spin down" the the Kickr prior to the test to ensure accurate data. At the recent BSX demo in Boulder, I had previous experience with the rider / subject. The numbers that were determined for him were entirely too high from both lactate and the BSX device. I later was told that the Kickr was reading about 25w high which would have put the rider in a range I could understand... but both the rider and staff were super-stoked on the numbers he "produced". I do use the Kickr for testing, but I always tell the subjects that they need to update the data based on the readings from their power meter. I have them push lap for each stage that we complete so that they can easily average that time frame. I also only use 1 of 2 Kickr's ( I think we have 10 floating around here) that I have personally ridden many hours and feel comfortable with the reported wattage.
This could create data that was either low or high.

2. I think it is difficult to be appropriately motivated for a ~20 min steady effort on an indoor trainer. I'm sure that some can equal their outdoor performance or maybe even exceed it, but the majority of people will not be able to hit the same numbers. You also have to wonder about cooling etc in the indoor environment.
This would cause the FTP number from an inside test to most likely be lower than an outdoor test.

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The above poster has eschewed traditional employment and is currently undertaking the ill-conceived task of launching his own hardgoods company. Statements are not made on behalf of nor reflective of anything in any manner... unless they're good, then they count.
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Understood, thank you for taking the time to explain it. As you mentioned, my kickr number differ greatly from the numbers put out by my stages. Probably because of the left-crank only power reading (left leg is slightly smaller/weaker than the right) causing a lower reading.

So I guess I'll just plan to do a test on the road to get the most accurate reading.

It isn't just your Stages. My SRM reads about 17 watts lower than my Kickr. Since the SRM is what I will have with me on the road, that is what I go by for FTP and the resulting zones.

The cool thing about watts is that watts will always be watts. So, if your FTP is 300 and you tested on a hill climb, it will still be 300 watts on the flats. You'll be going much faster at 300 watts on the flats of course, but that is why I hate looking at speed. Speed is just to emotional.

Mine are about 10-15watts different Powertap vs Kickr. I actually base that on my watts for a fixed HR, as I haven't done a truly equivalent flatland outdoor FTP test to compare against the Kickr.

I do think it's a good idea to do some sort of reference testing as race day approaches, whether it be a full out FTP test, or just correlating your HR to power numbers indoors vs outdoors if you do plan on racing via power. While 10 watts isn't a lot, if you're planning to ride aggressively, those 10watts can mean the difference between a total blowup on the bike vs an "A" result, especially if you're cracking past FTP with those 10watts.

Agreed that watts are watts. But my kickr can variate between a 5-45 watt difference at different intensities. But the one consistency is that the stages is always the lower of the 2. Like you said, as long as I go by the meter that I'll use on the road, I should be fine.

I just used my Kickr for the first time yesterday. I don't have a power meter on the bike I was using on the Kickr, but train with Stages on my other bike. It was pretty clear from the ride effort/resistance that the Kickr power reading was WAY too high (>50 watts), and I have no idea why. I didn't do a "spin down" before using -- is that needed for calibration?

It will help for sure and especially if you have not done one since setting it up. It may not perfectly align the two and you may have some other issues if it is 50 watts different.
The Wahoo website suggests one a week I think, but I believe even the Wahoo technicians are now suggesting a warmup and spindown before each session. At least the one I traded emails with suggested that.

my numbers between kickr, power2max and quarq are within 2% of each other (provided I let everything "warm up" for 15-20 mins before calibration/spindown). Having said that, some days they are wildly different to start with. So I never do anything where I'm counting on power (like an FTP test) without warming up and doing a spin down first.

I do all my FTP tests on the KICKR and use those numbers on the road. The KICKR usually seems to read slightly lower than my crank based PMs, which works out perfectly (since indoors feels harder to me).

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I have a Stages and SRM power meters on two different bikes that I use with the Kickr. The Kickr consistently reads 15-40 watts higher than either despite using the calibration kit and spindown. I had an original Kickr replaced because of this, but the replacement was no better as far as accuracy.

This week, I managed to modify the Kickr to work with a Garmin speed sensor. I can now capture all of my Kickr rides on my Garmin computer (power, cadence, speed) for a true record of the ride. Before modifying the Kickr, there was no way to send the speed data from the Kickr to a Garmin.

I continue to use the Kickr with Trainer Road and Virtual Training Apps controlling the Kickr in erg mode, but I only upload the ride to Strava using the Garmin as it captures the true power reading from the Stages or SRM.

I should note that with Trainer Road, there is a way to have the desktop app record the power from the SRM or Stages (or any other meter) rather than the Kickr. The Kickr won't match the external meter's power numbers in erg mode, but at least you can record the power accurately.

Wahoo do have plans to address this power discrepancy issue in future updates.

Definitely not. A lot of people who are new to power fall victim to the notion that they actually know their FTP. You don't. You know an estimation of it based on a testing method that is known to have error but is deemed "close enough" under ideal conditions. From there, your equipment and environmental conditions (especially temperature), what you ate, how much sleep you got, your freshness, and of course your fitness itself all have influences on the end result.

There is still value to the FTP as a benchmark for growth if it can be performed consistently in similar conditions, but the greatest value in training with power simply comes over time from having a solid familiarity with yourself as an athlete and knowing the types of numbers you can put out at different distances, intensities and temperatures. One of the biggest mistakes that athletes new to training with power make is thinking they actually know their FTP and driving their race head on into a brickwall because they did some 20' intervals and extrapolated that number and multiplied it by .85 and tried to ride exactly that in their race because that's what the formula said to do, even though they lack no practical evidence or experience that they're capable of holding it.

This is the long way of saying that your indoor trainer power doesn't matter as long as it is consistent as your indoor trainer power. Use it to stay motivated and grow over your indoor training season and don't worry about how it compares to your outdoor power because it simply doesn't matter.

For whatever it's worth, I have experience with both CompuTrainers and KICKRs and have had a few different Quarqs over the years. My Quarq always read 10-20 watts over my CompuTrainer, but is reads very close to my KICKR after properly warmed up and calibrated. Even when the two are reading almost identical, the feel of riding X watts indoors always feels markedly more difficult than riding the same wattage outdoors for me. That's just how ERG trainers are.

I would be keen to learn how you made these modifications to record speed on the Garmin.

To add the speed sensor to the Kickr, I used a Garmin GSC 10 sensor that I wasn't using and attached it as shown in these photos:

https://www.facebook.com/...e=1&l=b015e7cf87

I had also experimented with using the new-style magnetless Garmin sensors, but I couldn't get it to work consistently. Also, the only place it would fit was inside the upper belt assembly and even then there was a bulge when I reinstall the pastic cover.

The trick with adding the speed sensor, I found, was to find something that would work given the tight spaces on the Kickr. There isn't a lot of room to add a magnet that won't hit or rub. That's why I thought the magnetless sensor might be a good choice, but to no avail.

I also experiemented with adding the magnetless senor to the heavy flywheel. I estimated that this travels at 8x the speed of the casette/upper belt wheel, so I would adjust the speed sensor circumference value in the Garmin computer by dividing the normal number by eight. It kinda works, but it throws the balance of the flywheel off and the trainer becomes unusable. Also, the sensors have a hard time picking up a wheel moving that quickly.

So, once I determined that I was going to use the GSC 10, I had to determine the best place to mount the sensor and magnet. There may be better solutions, but I decided on the positions shown in the photos. The sensor position gives good visibility of the sensor and should allow me to change the battery without having to remove the zip ties.

To attach the magnet, I first disassembled the upper wheel assembly to see what was possible. Just sticking a magnet on the plate doesn't work as there is not enough clearance for the wheel to turn. This may be possible with very small, powerful magnets, but I didn't have anything small enough on-hand to try.

I determined I needed to drill a hole into the plastic cover of the upper wheel that a magnet could be placed into. If you look at the photo of the upper wheel with the plate removed you can see that the hole needs to go in one of the recessed areas.

I was able to fit a magnet very securely in a hole that was drilled. To help find the best location, I also drew a pencil mark by spinning the wheel with the pencil tip right at the notch on the sensor which is used to align the magnet.

Once everything was finished, I was getting 2x speed because the sensor was picking up the magnet twice as it passed by. The sensor isn't angled ideally with this setup (although it was the best solution I could find) which can cause this. I simply slid the sensor back a bit, though, until it only picked up the magnet once per revolution. (Pressing the button on the sensor until it turns red really helps when setting the magnets up. Once in this mode, the sensor light will flash green whenever it senses the magnet.)

thanks for sharing that. Much appreciated. I read the comments on your facebook pics and noticed the Beta version of software that allows the kickr to be controlled by a power meter. Is this something you can download or do Wahoo provide it to you??

No problem. I would contact them about the beta. I'm not sure I should even be talking about it that much, but it's pretty public knowledge at this point. Also, I should say that obviously if we put holes in our Kickrs we've voided our warrantees.

be interested to know what everyone is recording for slope readings when doing spindowns.

I was getting 1237 and it was taking 19.4 seconds. I was asked to tighten the belt to get it under 15 seconds and now have it at 1238 @ 13.7 seconds. I am thinking my kickr might be faulty.

I've owned my Kickr since September 2013 and have more than a week of time on it.

The offset has always been in the range of 1273 - 1276 with spin down of 25 - 30 seconds. Kickr power has always been very close to my zeroed and calibrated SRM -- the SRM is always within a few watts above or below the Kickr.

I'lll add that my SRM was sent in and calibrated late this summer. An uncalibrated, unzeroed SRM isn't the problem in my case. Also, I've done a lot of testing and my Kickr's power is hghly influenced by cadence.

My Kickr is usually 0-20 watts higher than my Quarq. Like someone else posted, it seems to vary with cadence.

Krispy2014 wrote:

To attach the magnet, I first disassembled the upper wheel assembly to see what was possible. Just sticking a magnet on the plate doesn't work as there is not enough clearance for the wheel to turn. This may be possible with very small, powerful magnets, but I didn't have anything small enough on-hand to try.

I suspect a 15 x 1 mm round rare earth Neodymium magnet and Bontrager ANT+ speed sensor secured to the non-drive side seat stay angled in so the sensor is within ~1cm of the magnet would eliminate the need to attach the sensor directly to the Kickr and could be used for rear wheel speed out on the road.

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Just got my kickr about a week and a half ago and have been struggling with the whole "it doesn't match" issue. I have a powertap and two quarqs, so I have some reasonable ways to test who is the oddball. One of the quarqs (road bike) is "new to me" and I've never directly compared to the others, but the numbers seem roughly right based on perceived effort. The other quarq (TT bike) and powertap have been checked against each other and match closely. My initial experiment with the kickr showed that it was reading ~20-30 watts higher than my quarq depending on the wattage and this seemed to be independent of spindown. I recently tried a slightly more detailed experiment with my other quarq (TT bike) where I had TR set to do a series of 2 minute intervals at 150, 180, 210, 240 watts. I got the following results for the lap average power as recorded from my quarq:


set1: 163 182 211 237
set2: 149 179 207 235
set3: 147 174 202 230
perfomed spin down thinking there might be temperature drift after ~20 minutes
set4: 142 165 190 215
set5: 141 161 191 218
set6: 136 161 191 214


I checked my quarq's calibration at the beginning, at the spindown and at the end and the calibration on the quarq seemed stable. The later sets were also physically significantly easier, so I don't think the quarq was at fault. These tests were all done at a similar cadence, between 90-100 the entire time. I didn't record the details of the spindown, but reading through this thread makes me think that might be informative. I think mine took roughly 25 seconds, read ~650 and was recording a temp near 40, but I could be miss-remembering. At the end of this I tried additional spin downs and couldn't get any better matching.


I have an open ticket with wahoo and am waiting to hear back. I like the kickr a lot, but this particular issue is pretty frustrating to deal with.

there is another rather long thread on this also ("Kickr reading high")

my experience has also been that the Kickr power reporting continues to drift higher even after 20 minutes, more like 40 minutes at least, maybe even longer (have not tried to quantify).

This maybe due to where the power is measured, i.e. directly from the cassette vs. the pedal. There is power loss in the transmission via derailleur/chain, etc. DC rainmaker did a good post on this.