Recently I’ve been struggling with FTP tests and TrainerRoad sessions. I put it down to the being knackered after my first 140.6 in the summer.
Tonight it suddenly clicked that previously I was using the power from the Kickr straight into TrainerRoad and now I am using the Stages on the bike to control the Kickr.
I thought my ftp was around 250W so this is the figure in TR for rides and the power level I was trying to “beat” when testing (yes I know it should be an all out effort).
Tonight I’ve done two 1/2 tests.
Test 1 - 5 mins in and my heart rate is starting to climb rapidly past 160 with my power slipping from 260 down to 220 - test aborted
Test 2 - pissed of with myself I give it another go, turn of the Stages control to see what happens. 10 mins in my heart rate is sitting at 150ish but my power is a steady 270ish W.
according to TR my LTHR is around 155 and in the second test after 10 mins it wasn’t climbing past this. 3 mins into the first test I was already at 165.
Can there really be a 40-50W gap between the Stages and Kickr.
Please someone tell me the Kickr is the more accurate
Do I now…
Re-test using the Stages to control the Kickr and base future sessions on that FTP?
Sack the whole indoor trainer test off and try to do it outside, subsequently using that FTP for the indoor (Stages controlled) and outdoor sessions?
Have an indoor and outdoor FTP figure for the respective training/racing. Natch the Kickr indoor figure will be the one I quote on ST
The full distance I did was using FTP figures based upon the Kickr figure of 250W but 70% effort (176W NP). I guess even if my FTP was only 230W then my overall effort would have been at 77% so not so hard it made much difference.
While I don’t have a Stages PM (two Power2Max units), I can commit on my n=1 experience with my Kickr and power reporting. I haven’t used Erg mode on my Kickr in a long time. After the reports of Kickr units reporting larger power outputs than power meters, I started to watch mine more closely. I would notice on mine at the start of a workout, the Kickr was always 5w or more lower than my power meter. About midway through the session it would report the same power, and by the end, it would report higher than my power meter. After this, I strictly run my Kickr in resistance mode, and only used the power from my Power2Max unit as I see this same power both indoors and outdoors.
Test with Kickr in resistance mode, not erg mode. If you are doing the 20min tests in TR, it should switch this automatically. If you aren’t running those tests, then set it to resistance mode manually.
Do either, but use the Stages output.
I see no need for separate FTP numbers. Get a number, train based on that number, raise that number, whether you are riding indoors or outdoors.
Unfortunately for you the KICKR and Stages are way less accurate compared to other power meters like PowerTap, Quarq, SRM, etc. 40-50W doesn’t surprise me at all.
I think you should always just use the Stages to control power. Why? Because it’s what you ride outside with, and race with. If you get different numbers indoors vs outdoors using the Stages, then yes, I’d recommend having 2 FTPs if the disparity is large. Heck, I have an indoor/outdoor FTP using my PowerTap and Fluid2 trainer.
So, re-test using the Stages numbers output. Test outdoors or indoors. If you do an outdoor test first, you know the ballpark for the indoor test. Usually I see less watts indoors.
An easy way to avoid the left-leg-only measuring error of the stages is to do a one-leg session with your left leg. That’d at least let you narrow down whether its all down to left/right imbalance in your pedal stroke, although you wouldn’t be measuring the same power region.
Edit: On second thought, this may not work. My understanding is that the stages power-calculator assumes constant angular velocity, which you normally have on a bike, but you probably won’t achieve single-legged.
Mine has a ~15w difference throughout a workout with stages being higher than KICKR. its a known error, i compensate for it knowingly outdoors.
All of my build training and measurement is done on the KICKR, so for FTP purposes it is the only # that really matters to me. In a race, the only number that matters for me is my finishing place, and i merely use power data for review after the fact.
Unfortunately for you the KICKR and Stages are way less accurate compared to other power meters like PowerTap, Quarq, SRM, etc. 40-50W doesn’t surprise me at all.
I think you should always just use the Stages to control power. Why? Because it’s what you ride outside with, and race with. If you get different numbers indoors vs outdoors using the Stages, then yes, I’d recommend having 2 FTPs if the disparity is large. Heck, I have an indoor/outdoor FTP using my PowerTap and Fluid2 trainer.
So, re-test using the Stages numbers output. Test outdoors or indoors. If you do an outdoor test first, you know the ballpark for the indoor test. Usually I see less watts indoors.
My Kickr reading is 15w too high (compared to a Computrainer and two Quarqs). I train against the lower number, but disseminate the Kickr number.
Go with 1) the Stages PM reading.
You may find your outdoor FTP test is slightly higher. I just use my indoor one and leave the disparity as buffer room to avoid overcooking the bike. E.g. if my outdoor FTP is 5w higher than outdoors, and I am riding a race at .8IF then I have a 4w ‘buffer’.
Did a test (again n=1) with Power Tap P1s and Kickr with latest firmware (after 15 min warmup and spindown via TrainerRoad). The final average difference was about 3 watts from the P1s to the Kickr. Prior to the spin down Kickr was reading 20 watts high. That being said if I only had left side power I would have been ~4% low (due to my L/R power imbalance). Are you doing a spin down after a good warm up? Below is a Chart showing left / right (if they were doubled) against total power. It also shows the error rate if I had left only compared to total power. You can see some left leg drills at the beginning where the chart drops off the bottom. I really tried to focus on keeping L/R balanced in the second half of the ride. I’ll try to post the P1 Power versus the Kickr Power if I can get them lined up.
I run stages and Kickr together. On flat ERG workouts with the kickr on a fresh warmed up spindown I only see a 2-3 watt difference over my intervals. I do see a larger difference on SIM mode rides because the kickr doesn’t do the peaks/valley of precision power meter. In this scenario the kickr over an entire ride usually ends up about 10-15 watts high on avg power.
I only monitor this from time to time just for curiosity sake. I would recommend like other to just use the stage power go forward. As long as it is consistent it doesn’t really matter if it is low/high. You can use the stages indoors and outdoors and have consistency in your readings.
While allot of folks don’t see huge power problems with the kickr I think based on user reports it is safe to say your kickr is more likely to be off then the stages.
Prior to the spin down Kickr was reading 20 watts high. That being said if I only had left side power I would have been ~4% low (due to my L/R power imbalance). Are you doing a spin down after a good warm up?
This. I say this in every one of these threads and I suppose here we go again. You need to do a proper WU and spindown with the KICKR every single ride if you are concerned with the accuracy, forget about the “once every few weeks” guidance from their website. This isn’t anything new or special flaw of the KICKR, this is has also been a required step for CompuTrainer’s for decades.
Not saying this will solve all your problems, there are another dozen reasons why two measures/estimations might not track that could be attributed to one or both units, but you need to at least do the proper calibration and see where you are.
