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Power reading accuracy

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Power reading accuracy

Old 02-03-21, 09:02 PM
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Yelhsox
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Power reading accuracy

Hey all! I got a wahoo kickr core about a month ago and have done a 4dp/ftp test and I just feel like the power reading is really low. I know there's a lot of nuances but I'll try to give you stats to base this off of.

I'm 83kg, can squat 205lbs and deadlift 260lbs so I think i have strong legs? I've been cycling for 2 years but only have doing it hard for the last 8 months or so. I've done a century ride and during good weather I was doing 25 mile rides 4x a week with a 40-80 mile ride 1x during the weekend. My ftp is measured to be 118W and I just feel like that's so low? I'll average like 98W on a 1 hr hard ride while my friend who I am much faster than outside and equal weight to averages 148W on her trainer. I just dont have much to base power off of but I feel like theres somethjng wrong with my trainer since I've done recalibration several times.

Let me know if I'm just weak please🤔. Thank you!
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Old 02-03-21, 09:14 PM
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try hopping on her trainer and see what numbers you come up with.

honestly, just because you can lift all of that i don't think it really means anything. unless of course you can continuously do that for an hour. i think cycling uses different muscles and certainly for much longer that just lifting.

and mind you, i am not saying you are weak. we all started at about zero at some point in time. i've been riding for years and when i finally had the chance to measure FTP it came in at 180ish. just keep riding but still compare with her trainer and see if there is a difference. it is always possible of a trainer malfunction.
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Old 02-04-21, 02:19 AM
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colnago62
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Muscle strength and cycling endurance aren’t that closely related.
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Old 02-04-21, 06:01 AM
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The strongest bike riders in the world have legs that are probably a similar size to your arm, so don't let the muscle thing fool you. Endurance sports are aerobic sports, not strength sports.

However, yes, 118 is pretty low for someone of your size and general fitness. I'd definitely think your powermeter is way off.

My own Tacx Flux is a consistent 10% low, but your sounds like there's a much larger error.

What speed can you do outdoors for an hour (average, not what you see on the computer at any given time)? This will give you a much better idea of your power.
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Old 02-04-21, 07:02 AM
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I use a Kickr and also use a Stages left power meter outside. My average numbers between the two are reasonably close.
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Old 02-04-21, 07:32 AM
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Is your firmware up to date? DC Rainmaker thinks it's pretty accurate.

https://www.dcrainmaker.com/2018/09/...uracy-analysis

Have you done a spin down? Some of the Kickrs need them to be done every once in a while.

https://support.wahoofitness.com/hc/...wn-Calibration
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Old 02-04-21, 09:12 AM
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I don’t know that there are any likely causes for a calibrated power meter to be way off, so I’d first look to the testing protocol for answers. How are you executing the FTP test? What kind of peak wattage are you seeing during the test? Does wattage jump all over the place in huge gaps while you’re testing?

If you can upload an FTP test file, we can take a look for irregularities.
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Old 02-04-21, 09:34 AM
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Thanks for all of your replies!

I do know that my lifts don't translate to better cardio performance and that the ftp isn't related. But I did want to include those to show that I'm not a couch potato and that I have a solid base in my 84kg. I do think that my lifts should help with my 5s power, which came to 530W. Meanwhile, before completing the 4dp, sufferfest estimated my 5s to be above 900W and my ftp to be 189W. So these low numbers are surprising.

I'm not by any means a great cyclist but if this helps at all my most recent outdoor activity was 43 miles, 1700' elevation gain, averaged 16.2 mph. I just think there's no way that a decent effort 1 hour ride would have any average power output of 98W, that seems sooo low. And my friend of the same weight and can outperform on hills and with speed, an easy recovery ride averaged 135W.

I have calibrated the trainer a few times now. I definitely know that when working correctly the wahoo products should be super super accurate, I just think I may have gotten an outlier here, I'm not sure.

Last edited by Yelhsox; 02-04-21 at 09:44 AM. Reason: provide more info
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Old 02-04-21, 09:53 AM
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The best way to find out is to ask a friend to either use their trainer OR hook up a friend's bike with an on-bike meter to a dumb fluid trainer or mag trainer then make a go at it.

Given the distances and mileages you claim, I don't see it feasible at all for the power to be that low. To go those distances and that speed for that one ride you mention at your weight..........it almost seems like the trainer might be reading roughly half.

I could totally see a lifter's 5s sprint power being just a hair over 1000w, with your 500w number being half.

Try to find a willing friend, then you'll know! Some folks online claim the sensor inside reading speed was bad within a week or so and led to low power readings. There was a new power supply brick for newer units around Fall 2019 also. The older bricks would fry the unit somehow. Need to make sure you don't have that issue also.

Good luck.
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Old 02-04-21, 10:11 AM
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Your numbers do seem really low. My wife is 54 and weighs 130 pounds and her FTP is around 140 Watts. If you have access to another power meter then that's probably your best bet. If there is a problem with your Kickr, Wahoo has pretty good customer support. At least in my case they did. I had major belt whine problems and one email with a short video attached to tech support and I had an RMA. Sent my unit off and got another one back very quickly.
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Old 02-04-21, 11:07 AM
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I agree 118w sounds low.

About lifting, everyone else is telling you it's not very closely related to squat and DL strength. That's because power is torque and RPMs together. If you can push down on the pedal with enough force to DL 500 pounds, and do it 90 times a second, that would be off the charts. 🙂
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Old 02-04-21, 11:52 AM
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Yep, that's too low.

As others have mentioned; Update KICKR firmware. Check YOUR settings in the App, make sure the app is up to date as well. Make sure height and weight are correct.

Do you run the app from your phone, laptop, tablet or head unit?

Do you have a Wahoo Elemnt or a Garmin Edge? Check you settings in those as well. Height, weight, FTP.

Right off, I'd put your FTP at 250. Put that into Strava, Wahoo (app for the head unit), Garmin Connect (and your Edge head unit if you have one).

You want all "user" settings to match. Again FTP at 250.

Setup for a trainer ride (after you've done all this), and connect to the app or head unit. Then if you're using Sufferfest find a workout that will have you ride for a steady length at Threshold, Sweet Spot, Zone 2 and maybe some sprints thrown in as well. With an FTP setting at 250 and using ERG mode you will know very quickly if your FTP is 118 (it's not) and just how close you are to a more real number. Then if you have a Garmin or Wahoo that can control trainers, I'd close the Sufferfest app and then run a workout on your head unit with THAT controlling the trainer. Again, test steady efforts at different levels (FTP, SS, Z2) and do some sprints.
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Old 02-04-21, 12:18 PM
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Are we playing The FTP is Right?!

I’ll put $5 on 210w!
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Old 02-04-21, 01:23 PM
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Originally Posted by chaadster View Post
Are we playing The FTP is Right?!

I’ll put $5 on 210w!
1w, Bob.
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Old 02-04-21, 01:51 PM
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Originally Posted by WhyFi View Post
1w, Bob.
I'll go 2w Bob (It's Drew now....ask me how I know )
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Old 02-04-21, 02:07 PM
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no one told me guessing was allowed.
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Old 02-04-21, 02:11 PM
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To get a better estimate of your FTP find a hill that takes 20-30 min to climb and ride it as hard as you can. The steeper the hill the better. kreuzotter.de has a decent calculator where you plug in your numbers and a power estimate will be provided.

On the kickr there is the standard spin-down which it sounds like you've tried. They also have a factory spin-down that can be used on occasion for a, supposedly, more accurate calibration. Wahoo can provide instructions for the factory spin-down.
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Old 02-04-21, 02:59 PM
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Originally Posted by gregf83 View Post
To get a better estimate of your FTP find a hill that takes 20-30 min to climb and ride it as hard as you can. The steeper the hill the better. kreuzotter.de has a decent calculator where you plug in your numbers and a power estimate will be provided.
You only really need a hill of about a minute that is over 7% or so grade and a day with next to no wind. Weigh the bike plus person. Go ride it. Create private segment and get time. Put time in bikecalculator.com

I'd put a beer on less than 40% of the US population being able to ride to a hill that takes 30min to climb out their front door. No driving to the spot. You must use existing ability to get there and back and climb it.
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Old 02-04-21, 03:02 PM
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Originally Posted by Psimet2001 View Post
I'll go 2w Bob (It's Drew now....ask me how I know )
That's what I get for guessing that when I wasn't last.

And I know that it's Drew, now, but... com'on. It's Bob. It's always Bob.
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Old 02-04-21, 03:45 PM
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Originally Posted by chaadster View Post
Are we playing The FTP is Right?!

I’ll put $5 on 210w!
Originally Posted by WhyFi View Post
1w, Bob.
Originally Posted by Psimet2001 View Post
I'll go 2w Bob (It's Drew now....ask me how I know )
Closest without going over, right? I'm in for 3 W.

(I've got a lock on this - you guys are going to get DQed for using lowercase w.)
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Old 02-04-21, 04:23 PM
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Do the advance spin down, aka factory reset, https://www.smartbiketrainers.com/ad...ickr-snap-4350.
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Old 02-04-21, 04:44 PM
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Originally Posted by gregf83 View Post
To get a better estimate of your FTP find a hill that takes 20-30 min to climb and ride it as hard as you can. The steeper the hill the better. kreuzotter.de has a decent calculator where you plug in your numbers and a power estimate will be provided.

On the kickr there is the standard spin-down which it sounds like you've tried. They also have a factory spin-down that can be used on occasion for a, supposedly, more accurate calibration. Wahoo can provide instructions for the factory spin-down.
I believe this adjusts the inductive braking force.
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Old 02-04-21, 04:59 PM
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Originally Posted by tomato coupe View Post
Closest without going over, right? I'm in for 3 W.

(I've got a lock on this - you guys are going to get DQed for using lowercase w.)
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Old 02-04-21, 06:20 PM
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OK thank you all for your help. You all have high hopes for me at 200W+... Unfortunately, I can't live up to that expectation. But fortunately for me, I think I've fixed my issue.

I performed the troubleshooting that wahoo tech support gave me and then did another spindown calibration.

I did the full-frontal test on the sufferfest just to check out if the problem was fixed.

I got: 5 sec power 657W, 1 min power 311W, 5 min power 221W, 20 min ftp 173W.

Keep in mind that this was all done on sore legs (did a one hour decent effort ride yesterday) and didn't do any of the prep that the sufferfest recommends beforehand, and that the 20 min ftp takes place after the other big efforts so the ftp found here is generally lower than other ftp tests (at least that's what sufferfest disclaims). I'm just excited that the trainer is fixed and I'll work on getting these numbers up going forward!

Anyway, thank you for believing in me. I may not have lived up to expectations but at least I'm not a couch potato with 118W :')
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Old 02-04-21, 07:18 PM
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Originally Posted by burnthesheep View Post
You only really need a hill of about a minute that is over 7% or so grade and a day with next to no wind. Weigh the bike plus person. Go ride it. Create private segment and get time. Put time in bikecalculator.com

I'd put a beer on less than 40% of the US population being able to ride to a hill that takes 30min to climb out their front door. No driving to the spot. You must use existing ability to get there and back and climb it.
A one minute hill won't give you much of an indication of your FTP. You might be able to compare it to the one minute power on the trainer but a 20 min test is better even if you have to drive somewhere.
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