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    Cycleops Trainer and Watt Output charts

    Does anyone have experience with the cycleops trainers and the watt output charts they provide for power? I have a Supermagneto Pro and am wondering if the watt output charts are accurate at all.

    Anyone try one of these trainers with a power meter to test out their watt output charts/graphs? I've searched and read quite a few articles and can't get a good answer.

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    I'm trying to prove that these watt graphs are accurate... That basically says the the Fluid 2 at 22mph is 300 watts of output... It seems really high. I'm just wondering if someone can verify that the information provided my cycleops is correct.

    Id like to have some faith in these power numbers before I start a whole offseason of training.

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    Senior Member Homebrew01's Avatar
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    Buy a used Powertap for $250 then you can use it on the road too with real numbers.
    Bikes: Old steel race bikes, old Cannondale race bikes, less old Cannondale race bike, crappy old mtn bike

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    Senior Member roadwarrior's Avatar
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    Quote Originally Posted by clones2 View Post
    I'm trying to prove that these watt graphs are accurate... That basically says the the Fluid 2 at 22mph is 300 watts of output... It seems really high. I'm just wondering if someone can verify that the information provided my cycleops is correct.

    Id like to have some faith in these power numbers before I start a whole offseason of training.
    See how long you can ride a fluid 2 at 22mph and get back to us.

    These charts were set up woth a power tap. Also, since you have a super magneto understand that 22mph in the road band is not the same as 22mph in the interval or mountain power band. Like 22mph is not the same when you are riding into a 20mph headwind.
    Last edited by roadwarrior; 12-11-12 at 05:13 AM.
    "Nothing is so typical of middling minds than to harp on the intellectual deficiencies of the slightly less smart, but considerably more successful."
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    Quote Originally Posted by roadwarrior View Post
    See how long you can ride a fluid 2 at 22mph and get back to us.

    These charts were set up woth a power tap. Also, since you have a super magneto understand that 22mph in the road band is not the same as 22mph in the interval or mountain power band. Like 22mph is not the same when you are riding into a 20mph headwind.
    Good info...especially the link above. Thanks.

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    If you don't ride on the road with power during the "on season", then who cares if the numbers are high or low in the off season - it only needs to be relative to your own training for comparison purposes.

    22mph on a trainer sounds about right for 300w, plus or minus 20w....my Kinetic is pretty close to that.

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    Quote Originally Posted by clones2 View Post
    Does anyone have experience with the cycleops trainers and the watt output charts they provide for power? I have a Supermagneto Pro and am wondering if the watt output charts are accurate at all.

    Anyone try one of these trainers with a power meter to test out their watt output charts/graphs? I've searched and read quite a few articles and can't get a good answer.

    I have the cheapo Cycleops Mag trainer and had the same thoughts you did about trying to get both accurate (comparable to a power meter) and precise (comparable to yourself from one trainer ride to another). I want accuracy for simple curiosity's sake, and precision for measuring training improvements over time. The simple answer is that yes you can have both accuracy and precision from many trainers but if all you rely on is the manufacturers virtualpower formulas you will get precision and might or might not get accuracy.

    So, I borrowed a friend's PowerTap about a year ago. I did multiple trainer rides of 20 minutes or more, had my wife do some as well, and my son, and my nephew, and recorded all of them along with the power and speed information. The rides were done on settings 5, 4, and 3 for the Mag trainer (I wasn't interested in 2 or 1). From that data I calculated the power curves for my trainer using that PowerTap wheel and tire (Excel has a feature that automatically calculates the curve once you put the data in a scatter chart so it is actually very easy to do this) and came up with:

    Resistance 5: Power=17.819*Speed-88.651
    Resistance 4: Power=12.558*Speed-76.463
    Resistance 3: Power=9.4939*Speed-55.134

    I make sure to set up my tire pressure, and the tension on the trainer the same way each time. Then I used the formulas to compare to the original PowerTap data and the calculated data was within 3% (actually closer than that) of the PowerTap data.

    About a year later a friend's bike was making a layover in my house and it had an SRM on it. So I hooked it up to the trainer and did a 20 minute ride and recorded the data. Then using the above formula for the 4th resistance level I compared the SRM Power with the Calculated/Virtual Power and the two were within 2 watts on average power and when looking at the line charts you couldn't tell which was "real" power and which was "virtual" power.

    So, real world repeatable results, rather than anecdotes and pull from the air opinions, show you can have accuracy and precision for speed to power conversions on at least the trainer I am using (I did the same thing with a set of rollers I have but didn't double check the formula with the SRM when I had it). The Cycleops chart however does not seem to match up with my testing.

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    I keep seeing reference to tire pressure and trainer tension affecting power readings and I'm trying to wrap my head around why that would be the case. Once you have solid engagement of the tire with the roller on the trainer (i.e., no slipping), do the tire pressure and trainer tension really matter?

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    Quote Originally Posted by svtmike View Post
    I keep seeing reference to tire pressure and trainer tension affecting power readings and I'm trying to wrap my head around why that would be the case. Once you have solid engagement of the tire with the roller on the trainer (i.e., no slipping), do the tire pressure and trainer tension really matter?
    Both of those factors affect the rolling resistance of your tires. And on a trainer in the absence of wind resistance the effects of rolling resistance are a larger percentage of the over all resistance you are up against.

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    Quote Originally Posted by svtmike View Post
    I keep seeing reference to tire pressure and trainer tension affecting power readings and I'm trying to wrap my head around why that would be the case. Once you have solid engagement of the tire with the roller on the trainer (i.e., no slipping), do the tire pressure and trainer tension really matter?
    I don't understand the physics behind it (and haven't tried to) but I did do some testing between turning the tension knob 2 full turns versus 2.5 full turns and it seemed to make a couple of watts difference (but that seems to be within any reasonable margin of error too). This was before I had finalized the formulas I came up with so the formula I was using wasn't as accurate as the one I ended up deciding was my "final" version but the formula I used was based upon 2 turns of the tension knob. I didn't keep the original data but did find some charts I did at the time using the same formula but different tension. I never tried different tire pressures:

    Resistance 5 - 2 Turns.jpgResistance 5 - 2.5 Turns Turns.jpg

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    So if you're using a power meter for power (as I am), it's really a don't care because it doesn't affect the power meter reading -- but if you're using trainer speed as a proxy for power it can make a small difference. The rolling resistance explanation makes sense. Thanks!

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    I think the chart reads too high! On a Computrainer, my FTP is 260W. Doing the same test on my Fluid2 trainer my FTP magically increases to ~300W according to that chart.

    Hopefully getting a real power meter next year to compare...

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    Fwiw I tested my KK Road Machine against a PT tonight and per the calc on the Kurt site they agreed 23mph=360 watts.

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    Hi. I know this post is kind of old.
    I tried your your formulas to calibrate my power on my trainer. But the power profile for Resistance 5 gives you negative power under 5miles/hr. Is this correct? Or I'm I using your formula wrong?

  17. #17
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    Quote Originally Posted by rsanchez056 View Post
    Hi. I know this post is kind of old.
    I tried your your formulas to calibrate my power on my trainer. But the power profile for Resistance 5 gives you negative power under 5miles/hr. Is this correct? Or I'm I using your formula wrong?
    Assuming you're replying to clint after all these years, of course that is how it works out. Look at the formula. You're using the formula correctly, however the formula is nonsense.

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