Power Meter Readings On Trainer Hugely Different (~50-100%)
Made the switch over to the trainer this weekend (it's in the 30's in Wisco already). This season I purchased a Power Meter and have been training on it for months. But, this will mark the first time I have had both a Trainer (Kinetic Road Machine) and a Power Meter (Stages Crank Arm) at the same time.
I have seen a bunch of the forum posts about differences between riding with power on road vs. trainer, as well as articles on internet... and have learned
1) You can expect a difference in wattage between the two
2) There is no "normal" difference between riders (ie. some are higher/some lower)
3) There's a lot of factors influencing this (ie. flat surface, cooling, core strength... etc)
In everything that I have read (and in conversations with others) it seems that +/- 10% ish is somewhat common.
My power seems way off (estimated between 50% and 100% off). I say estimated, because I know the trainer will feel different, but I really have no idea how to quantify accurately. All I can say is that I was felt like I was pushing an easy 150-160 watts yesterday and it was reading below 100. Am I losing my mind??? I zero calibrated my power meter. I took my bike off the trainer and re-installed. I watched some videos to confirm correct installation, but still seeing similar results. Potentially important other details to note: I took a little bit of a hiatus after my HIM on Sept 29th. So admittedly I have some kinks to work out.
Here's what I can gather are potential evaluations of my situation :
1) I am crazy. This is all in my head. I need to stop wasting time and get back to work.
2) This is a "perfect storm" of factors that are adding up to a bad power reading (ie. I'm a little rusty after my break, my trainer is old, too much air in my tires, normal variance between road & trainer... etc), and I just need to ride through it.
3) My trainer is old and has malfunctioned somehow. This seems somewhat absurd.
Any Advice / Experience from teammates or WSM's to help would be hugely appreciated!!!
Comments
I have a new Cyclops Hammer direct-drive and have made many attempts to calibrate my SRM PM (very accurate) with numerous Apps. The Apps are consistently 10-20w (5-10%) below my head unit. I’d love to correct this, but its easy enough to adjust the FTP settings for workouts, “drop a little weight” for Zwift racing, and my biggest problem is that my Strava posts are inaccurate!
Over the years (and with a big fan) I’ve been able to reduce the difference between indoor and outdoor FTP to <5%. In my case, engaging the upper body, fighting wind, and rocking out-of-the-saddle outside are probably inefficiently burning matches anyway.
I had to get rid of my 20+ year-old Computrainer... and from what I read, the power units DO lose accuracy over decades ;-) Wheel-on units are more difficult to calibrate in the first place.
While I don’t have a solution to your problem, the take-homes are 1)You are not crazy 2) It is not all in your head and, and over course, 3) Get to work
@Rob Tune Are you getting your power from the Stages when you are riding inside or from the trainer? If the power is coming from the Stages in both cases there should not be much difference. Maybe if it's a wheel on trainer there could be some slippage, but that should be pretty obvious with that much difference. I do think riding inside can feel much harder than outside at times.
@Sid Wavrin Power is coming from the Stages meter when riding outside and on trainer. I agree, I was expecting a small difference (ie. 10%) but this seemed weird.. . I think I am going to re-assemble the trainer, re-install my bike, and then get back to work. Maybe it will sort itself out. Thanks!
Thanks @John Culberson! I'm with you... doesn't really matter as long as I'm putting in the work!
Here's a few things.. you aren't crazy. My Indoor FTP is lower than my outdoor by as much as 10-15%.
that said, I ride a kickr trainer and I use my PowerTap pedals as my power meter. Zwift adjusts my Kickr to read power output at the pedals. The SAME pedals I use when riding outdoors. Thus i am only using one power meter. Not clear if you are having your program (trainerRoad, Zwift, etc) get it's power input from your trainer or your bike's PM.
Getting used to how much harder a trainer is becomes an art. unlike outdoors, you never coast. Also a significant amount of energy is used in cooling yourself, that's part of why on a hot humid day you output less watts than on a hot dry day.. Fans (multiple) are your friends, lowering the ambient room temp of your workout space helps also.
as others said above, finding a new "indoor" index, will also help you, as long as you are seeing a good tie in of RPE and HR, watts becomes the third input..
keep riding, keep tinkering, keep asking your teammates questions!
@Rob Tune : Doesn't REALLY matter... but I have noticed that the difference in my head unit and the Zwift power sometimes seems to become greater as the ride progresses (and I get more tired). Its hard enough to hang with the group on a Zwift race without having to ride a flat to the finish line! I download my head unit for TSS, so my training efforts are measured accurately.
@John Culberson if you set zwift to read the same power source as your head unit, the TSS calculations should be the same..
I'll give that a try, thanks Scott. The Smart trainer is receiving input from Zwift to control resistance, so I just assumed that Zwift would reflect the power reading from the trainer. The calibration process using Zwift has been less than satisfactory for my Cyclops M2... the 20lb flywheel spins until time out. Those of us in the Grand Master" age-groups struggle a bit more with the technical aspects of the sport ;-)
@John Culberson @scott dinhofer @Jeremy Behler @Sid Wavrin
Spoke with both Kinetic and Stages yesterday and isolated the issue to my power meter. That said, I did some tinkering at home, performed another zero reset, and I think we're back in a range that makes sense.
Next steps: Ride hard, Get a fan, Re-Test FTP for Indoor (in a week or so to give myself some time to get more comfortable and to get back into a rhythm).
Psyched for some durability and OutSeason work. Big Goals next year.
Thanks to everyone for helping me out!
@rob tune For the fan. I have tried a few but I really like something like this: https://www.amazon.com/B-Air-VP-25-Damage-Restoration-Plumbing/dp/B01DFW2BQA/ref=asc_df_B01DFW2BQA/?tag=hyprod-20&linkCode=df0&hvadid=194946745349&hvpos=1o2&hvnetw=g&hvrand=287741187157281221&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9031293&hvtargid=pla-334744374234&psc=1
It moves a legit amount of air. It is relatively quiet for the power. It makes a big difference over just a box fan or a fan on a stick. I picked mine up at Home Depot. It wasn't this much. But this was the style.
@matt limbert That thing doesn't mess around
@matt limbert - that's truly industrial strength!! I've gotten a couple of the Dyson fans on sale. They are pretty good as they move a decent amount of air and are quiet. they also have remote controls so I don't have to freeze during my warm up!
Dual remote Dyson = optimal Pain Cave work. Wicked Smart
@Rob Tune
Lots of good info above, so I'll add just a little.
The road machine, being a "dumb" trainer obviously doesn't provide variable/controllable resistance. I started with this trainer. And also with the Stages crank arm power meter. I found that I needed to put 100-105 PSI in the rear tire and crank down the turn knob 2.5 turns after initial contact between the roller and tire. And I needed to connect with Zwift via ANT+ and not Bluetooth. Used a long USB cable and ANT dongle. There shouldn't be a difference, but I found the Bluetooth was sketchy. Could be a Stages thing. While I noticed a difference between the trainer and the road, it wasn't really all that much. It is also imperative that you calibrate/offset the PM before every ride. Some suggest riding for a minute or two and putting in a handful of 10 second sprints, then doing the calibration. I've tried it that way and just calibrating before riding at all. I haven't noticed a difference.
I later switched to a Kickr Snap when REI had one of their 20% off semi annual sales. There should be one coming up very soon. Now this is where I really started to see a difference between the trainer and the power meter. Like crazy differences. I have the previously mentioned Stages crank arm, a Rotor InPower on another bike, and Assioma pedals on another. I notice no difference between the 3. They all ride/feel identical regarding power. But, the Snap is another story. If I use the Snap as power source and obviously the controllable trainer once I start to exceed about 180 watts, the Snap reads well below. Like insanely below. Example. If I am doing an interval at 270 watts (pedals, stages, InPower), the snap will read low 200s. I monitor the various power readings via Zwift, watches, and Edge 520. And if I'm doing some 300+ watt short intervals (FTP 275), the Snap will be lucky to read 250. So I always connect to Zwift with the Snap as the controllable and the PM as the power source. This way it doesn't matter what the Snap is "reading" as that info isn't transmitted to Zwift. The power at the PM is accurately controlling the Snaps resistance regardless of what the Snap says its power is.
A couple weeks ago the battery died on my PM right when I started. Being a lazy SOB I didn't feel like changing it, so used the Snap as the power source. I couldn't do the workout as proscribed. When I had to ride 250 watts, in reality I had to put out over 300.
If you've got the budget, I'd get the Snap when REI has their sale.
I've ridden 4,300 miles so far this year. Over 3,000 of that on Zwift. I'm a trainer dog. And with the Snap I don't really notice a difference in my legs or HR between the road and trainer.
Thanks @Brian Terwilliger , that post was really helpful!
Happy to say that I had a 2.5hour ride this morning in the cave and my power actually felt spot on! Really happy.
Just purchased the Kinetic R1 Rock N Roll Trainer. I have been using a Powertap Hub with a Cycleops Fluid Trainer. It has been working good but wanted something with the rocker type motion and also wanted something direct drive to eliminate wheel slippage. Did not want to go to just a rocker plate as it seemed to me that the frame would still be fixed in a way that causes unusual torque on the frame. I have an old Cannondale aluminum frame that I have been using on the trainer but wanted to use my Speed Concept to have more race specific training. The rock n roll motion of this trainer seems to take at least some of that unusual torque away like I wanted it to.
Now for power. I was hoping to not need a power meter but knew I had my P1 pedals just in case. Well I started riding and I felt like I was pushing way more power than it was showing me on Zwift. I had a hard time getting the Kinetic Fit App to work but finally did. I tried to update the firmware and got it to start the process but it gets hung up and just will not finish updating. I was finally able to do a calibration and was hoping that would work. I knew something was wrong so let's test the pedals. I put them on and used my 520 to read the pedals and Zwift to read the trainer. The trainer was reading about 50% of what the pedals were reading. No wonder I felt like I was pushing way harder than what was showing. I have previously tested the pedals against the hub and they are within about 10 watts at about 180 to 200 watts. To me that was acceptable and easy to make adjustments for.
Given all of that, I gave up on using the trainer for power and am using the pedals for power until I can get similar power readings from the trainer. Although, given the above comments, that may never happen. Not sure what else to do. The setup with the pedals worked great and I love the direct drive and the rock n roll. Just seems like such a waste to have the smart trainer and not really be able to use it for power. It does seem to be working with Zwift as a controllable trainer so that I can "feel the hills." I can use it as basically a dumb trainer or a controllable trainer.
I don't think any of this is new information but just sharing my experience and how I am working through things. If anyone has any advice on updating the firmware please let me know. I am going to put in a support question to see if they can help but we all know how that usually goes.
sounds like a great purchase @Bill Eckert - being an owner of three kickr's I just got the Inside Ride setup for a kickr. have only done one ride with it so far, but hopefully this is a game changer that engages more stabilizer muscles so I am not so sore when I first head out on the road in the spring.