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  • - In this video, I wanna talk about gear selection

  • and it's affect on power accuracy.

  • Is a trainer, more accurate in the small chain ring

  • than the big chain ring or vice versa.

  • In other words, how does flywheel speed affect

  • power accuracy.

  • Does it even matter?

  • In the past few weeks I did a lot of riding

  • and I crunched through a lot of data

  • from two different trainers,

  • three different power meters,

  • and two different bikes,

  • and I did the same workout six times.

  • That's over six hours of riding.

  • And hopefully I can answer this question or maybe not.

  • But let's dig into it,

  • or I probably should say

  • let's try to dig myself out of that rabbit hole.

  • (bouncy lounge music)

  • - Hey what's up guys,

  • This is Tariq here from smartbiketrainers.com .

  • Thanks for joining in.

  • If this is your first time here,

  • this is where I talk about smart trainers and fitness tech,

  • and if you want to learn more about indoor training

  • and smart trainers,

  • and see more content like this,

  • hit that subscribe button.

  • And if you find this video helpful I would appreciate it

  • if you hit the like button

  • and tell your friends about this video,

  • and share it on Facebook, Twitter and uh, everywhere.

  • So some chatter's out there on social media

  • and different forums that the trainer measurement might be

  • more accurate in a smaller chain ring

  • than the big chain ring.

  • Basically your smart trainer is much better at calculating

  • power at low flywheel speed in ERG Mode,

  • than a flywheel- than a fast flywheel speed.

  • Let me explain.

  • Now probably the reason for this is we did have some

  • trainers this year from certain companies report different

  • power at different flywheel speed.

  • And one of them happened to be the Tacx Neo,

  • or Tacx Neo 2,

  • and the Tacx Neo has that reputation for being the most

  • accurate or one of the most accurate trainers in the market.

  • So when you are riding on your smart trainer

  • and have your bike in a smaller gear,

  • like a small chain ring in the front,

  • and the middle to bigger cog in the rear,

  • the flywheel isn't going to be spinning as fast

  • and the trainer will have an easier time adjusting

  • resistance in ERG Mode to keep you at your target watts,

  • and you're gonna see smoother lines.

  • Also that's why many riders complain and wonder why

  • their average speed is so much slower indoors in ERG Mode,

  • but that's a different topic.

  • However if you use a bigger gear,

  • the flywheel will spin a lot faster and the trainer will

  • have a harder time adjusting resistance,

  • and because of that,

  • you will see more fluctuations in power like you see

  • in this chart right here.

  • Now power lines might not be as smooth in the big ring

  • as in the smaller gear,

  • but this is not what I'm talking about here.

  • I am more concerned about power accuracy.

  • And I talked about ERG Mode and the differences between

  • a small and a bigger ring in a little more details

  • in this video right here.

  • You can go and watch that one after you finish watching

  • this video,

  • if you feel like binge watching ERG Mode stuff today

  • instead of The Office or Netflix or any other show,

  • and I will link to that video in the description below.

  • So I ran a bunch of tests,

  • and the main one I did was a three by ten minutes,

  • and I wanted to look at power averages and I wanted to

  • collect data from longer intervals,

  • and use three different gearing combinations.

  • Power fluctuates and different power meters measure power

  • at different points,

  • so I wanted to have a larger data sample to better measure

  • the effect of flywheel speed on power measurement.

  • Hopefully that makes sense.

  • So I ran the tests on the Neo 2 and Wahoo Kickr 2018 model.

  • The power meters I used, Power2Max on my tri-bike,

  • and I also have another Power2Max power meter

  • on my road bike.

  • The Assioma pedals Duo that I switch between the two bikes.

  • And to set a base line, here's a ride I did.

  • This is just a regular ride using all three of my

  • power meters so as you see they were very close.

  • The Assioma was a bit higher which was expected because

  • it's a pedal-based power meter,

  • and pedal-based power meters usually measure power

  • closer to the source.

  • And the averages for this ride were 180 for the Neo,

  • 181 for Power2Max and 183 for Assioma.

  • So on the Kickr I did the first ten minutes in a small gear.

  • The Kickr average flywheel speed was around

  • thirteen miles per hour.

  • The second interval flywheel speed,

  • average 19 miles per hour and the third interval

  • in a big gear,

  • average flywheel speed 29 miles per hour.

  • And when comparing the power measurement between all three,

  • my Power2Max across all three intervals was off by

  • only 0.41 percent.

  • So that's really close and based on that,

  • we can say the flywheel speed or gear selection

  • had no effect on power accuracy.

  • But let's keep going.

  • The Assioma was a different story.

  • Even it though it was calibrated however it was measuring

  • between three to four and a half percent higher,

  • so we're talking about eight to eleven watts higher

  • for a ten minute interval.

  • Let's take a look at the Neo 2.

  • My Power2Max was consistent throughout all my rides.

  • In a small gear or the lowest flywheel speed,

  • it was reading a bit low.

  • We're talking about one and a half to three percent lower

  • across all three different workouts.

  • The second interval in a- in the big ring,

  • the flywheel was reporting a speed of around

  • 20 miles per hour,

  • and power measurement was spot on.

  • Then at a higher flywheel speed it was a little bit higher,

  • but not much higher.

  • We're talking about three watts higher and was even spot on

  • on the third ride I did.

  • The Assioma however was reading a bit differently.

  • It was spot on in the small ring but measured a little bit

  • higher at a higher speed or the- went up in a bigger gear.

  • But it was still within acceptable range.

  • But then up to five percent higher when going to a very

  • big gear and the flywheel speed was running around

  • 27, 29 miles per hour.

  • So looking at all three rides,

  • I think we can say flywheel speed did not have,

  • did not really have an effect on power accuracy

  • when comparing it to my crank-based power meter.

  • However when looking at the Assioma pedals,

  • you might arrive at a different conclusion.

  • Now according to Favero,

  • their pedals have instantaneous power system,

  • or as they call it,

  • instantaneous angular velocity or IAV.

  • Meaning their pedals measure power instantaneously

  • throughout the pedal stroke,

  • where other power meters calculate power using the

  • average angular velocity per rotation.

  • And according Favero, this might introduce

  • an additional error up to four and a half percent

  • compared to instantaneous power calcualation.

  • If that is the case then that might explain why the Assioma

  • might measure a little bit higher or different than

  • a smart trainer or even different power meter

  • in some situations.

  • If you have an Assioma Duo let me know if you notice

  • the same trend.

  • If you wanna run the same workout I did,

  • I will link to it down below,

  • and I will have it on smartbiketrainers.com as well.

  • So here are my takeaways.

  • As long as you have a good trainer,

  • meaning it's not a defect and calibrated correctly,

  • it shouldn't really matter which gear you select.

  • Power measurement should remain consistent regardless of

  • your flywheel speed.

  • When in ERG Mode the general rule is to stay at a low gear

  • for a more responsive trainer,

  • whether you like the big chain ring or the small chain ring,

  • shift to the middle of the cassette

  • and keep your chain straight.

  • This will also give you a quieter trainer,

  • and minimize the stress on your chain and that will give you

  • the closest power measurement to your power meter

  • regardless if you use a crank-based or a pedal-based

  • power meter.

  • Find a gearing combination that feels more natural to you

  • and use that gearing combination.

  • Stay away from uncommon gearing combination

  • like a really big gear or a really small gear

  • like I did for this test,

  • unless of course there is a floor wattage issue.

  • Some trainers might have mechanical limitation that might

  • prevent you from hitting your target whilst you're in

  • recovery intervals.

  • In that case switch to a smaller gear.

  • Okay.

  • Hope you find this video helpful.

  • If you did, hit that like button and subscribe.

  • That's all I have, thanks for watching

  • and see you in the next video.

- In this video, I wanna talk about gear selection

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B1 中級 美國腔

ERG模式。飛輪速度是否影響動力精度? (ERG MODE: Does FLYWHEEL Speed AFFECT Power Accuracy?)

  • 1 1
    Henry 楊 發佈於 2021 年 01 月 14 日
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