I started off with a Tacx Vortex “Smart” trainer. It’s been fine. It served it’s purpose and I don’t ride the trainer that much anyway.
I got extra serious again with cycling a couple of years ago. I finally got a Stages Campagnolo left. Yes, I know people have complained about left only, left/right balanced, and all that. For my purposes, I still think left only would be fine.
But, but, but … my best 20 minute power on the Tacx was 295 watts. I haven’t tested for six months on the Tacx (Corona and all). I’m clearly fitter now than when I did a 295 watt test and my best outdoor power on the Stages is 220 watts.
I did try to do a side by side comparison with the Stages vs. Tacx and they seemed close though power bounced around a lot. I didn’t record simultaneous sessions though because I think I need two Garmins for recording and DC Rainmaker’s tool.
On one hand, it’s a blow the ego. I thought I was closing in on a 300 watt FTP. I do seem way stronger than a 200 watt FTP guy. I’m one of the stronger old geezers in my club (age 54) and I have 30+ KOMs on Strava. I have great short power and can score on the shorter segments but I also have a bunch of 10-12-20 minute KOMs on gravel which are blasts near or above threshold.
Maybe I’m venting more than anything. I find this whole power meter thing frustrating. Ideally I want power on my gravel bike and on my road bike but getting two meters that are very close seems like a crap shoot.
If I didn’t care about the actual numbers I could just use the Stages for indoor and outdoor riding and then just look at it as a relative number. It just sucks that there seems to be such a large, 75+ watt, discrepancy between the equipment that I have.
I went with Stages because of price and that it was Campagnolo. I really wanted a Campagnolo crank on my Campagnolo bike and the other Campagnolo options are around $1500.
Just throw the bike with the stages on the trainer. Pair your Garmin to the Stages and run the TrainerRoad App paired only to the trainer. Then compare the two rides.
This will record both for the entire time and you can see
Switching power-meters won’t solve the problem - you’ll still have two different measuring devices and they won’t match 100%. I love Power2Max and dislike Stages - but there’s no reason to drop your Stages based on the information you currently have - just compare them to each other
Also - what you propose about just using the stages is correct. You should try to use a single power source when possible - so after you’ve done the comparison ride(s) I’d suggest you use powermatch with the stages numbers controlling the trainer resistance
You need to establish an FTP test protocol (same test, similar conditions) and repeat that test a few times to actually determine your FTP. I have a stages, a kickr core and Faverro Assioma pedals and they all read different by about +/- 5% of each other on any given day.
Just a comment re using Ray’s analyser tool, if you can access your trainerroad files via windows you can download a ride as a fit file which the analyser can use, therefore you only need one garmin. So perhaps have trainerroad reading your trainer only and the garmin on your meter, then use those files for comparison.
Yea 25% would be a bit much between power meters but to me it sounds like there are just too many different variables in your situation to compare your two numbers. When you start adding up inside vs outside, power meters, time, etc. then the differences could really account for what you’re seeing.
Don’t get discouraged! One time I ramp tested at like 213 FTP (indoor) about a week after doing 260w for an hour. Even now, on any given day I can probably do about 10% higher outdoor than I can indoor.
What matters is consistency, reproducibility and repeatability.
Oh and if you’ve never used it before - DC rainmaker analyser…superb! I wanted to compare some power meters, paid USD 5 for 24 hr access and so easy to use. However watch YouTube video first for how to use (I needed it to match up slight time differences on the files). Highly recommend
Your timing and problem is very prescient. I have a Tacx wheel on Flow 2200 with a PowerTap hub wheel set on my inside bike (actually a TT machine that like me is locked down) and I have a training bike with a Stages 2nd Gen Ultegra L/H crank on it.
Intrigued I did my last FTP test with the Powertap wheel and Stages crank on the same bike on the turbo and found that there a good 30-40w difference.
So inside my FTP is higher. My solution was to use two different FTP values one on each bike.
For what it’s worth I’m 99% certain that my difference is due to a knee injury in my left leg so that IS less powerful than my right leg, so double weak leg is lower than weak and strong leg combined.
Currently lots of left leg physio.
Also I’m prepared to bet the Vortex is wildly wide of the real power, mine certainly is and sadly it over reports to flatter my fragile ego.
watts.pw does the same thing as the DC rainmaker tool and is free. I lent my Direto trainer to a friend who had a cheap wheel on trainer and he found his power was down by almost a quarter.
I’ve used the Zwiftpower one before. Im not totally sure how it works, I think someone else (i.e. a Zwiftpower moderator?) needs to come in after the fact and clean up the analysis. When you first upload two files, they are usually wildly off. After some time the analysis is not “pending” anymore and it’s cleaned up and much closer.
I’ve been using the ZwiftPower comparison and have no complaints. You just need two .fit files and match the times if the files started at different times. I download the .fit file from TrainerRoad after I’ve completed the workout and the second file comes from either Garmin Connect or Zwift itself.
I’ve got a kickr indoors with one bike, and I’m using garmin rally XC200 pedals on another bike outdoors. I’ve calibrated the pedals. I’m seeing about 30 watts higher outside. There’s a few obvious differences here. The pedals are measuring power before the the drivetrain, the kickr after the drivetrain, so any inefficiencies in the drivetrain taken away from my power on the kickr, and not the pedals. The set up on the two bikes may not be the same. I think big part of might be mental, and just putting more gusto into it outside. But 30 watts is pretty big difference. I’ve toyed with putting the pedals on the trainer, and seeing if I can get a record of the power from both the kickr and pedals on the same workout.
I could put the outdoor bike on the trainer, that would remove a couple of variables (it’s just so convenient to have one bike permanently mounted on the trainer)
I’m about to get a measuring tape and compare the relative positions of the saddle, pedals, and handlebars on the two bikes.
I might have missed it. Are you nailing the workouts at 295 on the taxc? When using the stages with TR is it hard or easy?
My stages one sided power meter on the gravel bike differs from my S2 trainer which is different than my road bike dual sided set up. All three different bikes.
And…. It doesn’t really matter to me. It’s an approximation and my workouts are the proper level. I’m also still able to hang with the fast group. Some
Of that is just better bike handling but nonetheless it is a number that doesn’t define me.
Well, at least until the next FTP tests. Seriously, unless you are get a jersey with your ftp on it I’m not sure it matters. It’s likely in between.
How’s your indoor environment for cooling. I can mentally put out more indoors than out when I’m not worried about traffic and falling off etc but most folk put out more power outs doors where you have natural air conditioning/ cooling.
My trainer is on my sun porch, which is plenty cool in the winter (during a hot day in summer, it’s just about usable). I have two high volume fans blowing on me. I did an outside ride on Saturday where my average power was over 50 watts higher than any average I ever saw on the trainer. It was a very nice cool day though. I realize average power isn’t a perfect measure, but still: 50 watts!
I suspect the difference is explained not by any one thing, but several things. The fit on the trainer being less than optimal, drivetrain issues, maybe cooling issue, maybe differences in the power meters, probably a few things I haven’t wrapped my head around yet.
I’m working on making the fit on the trainer match the outdoor bike. The fit on the trainer really leaves something to be desired.
