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SRM power spikes???

Started by wilmar13 · · Last activity · 7 posts · 1,417 views

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01 / Original postSRM power spikes???wilmar13 · 7 Jan 2007 02 / This pagePosts 1–7Page 1 of 1 · chronological order 03 / Latest replyPost #7bikeguy · 7 Jan 2007

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Power meters
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7 January 2007
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7 January 2007
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wilmar13
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  1. Original post
    wilmar13
    Archived post
    #1

    I was a very good boy this year so Santa brought me a SRM DA crankset to upgrade from the Polar I have been using...

    In general they seem to read about the same, although I have not had any good rides to compare 20MP, etc. (if anything the SRM reads a tad lower)... But I have never seen power outputs above 1200 watts with my polar, and it is relatively easy to do with the SRM... as a matter of fact I have gotten above 1800 watts for 3 data points (@1 sec interval). I understand that Polar takes a 5 second avg so that I never saw these peaks, but I don't have a particularly strong sprint so these numbers seem high compared to what others have posted (I am 85 Kg).

    For example today I jumped into the draft of a passing minivan producing a 5 second avg of 1183 watts (1645, 1562, 1023, 978, 707) . Is this real or is were the first 2 seconds garbage? I mean a 5 sec avg this high with my Polar would have been pretty hard... not that it was easy today but I didn't need to dig deep into my suitcase of courage or anything. If I throw out the two high numbers and do more like 1000 watts it results in 5 sec power of ~950 watts, which seemed more like the effort based on my Polar experience.

    What is confusing is that 300 watts feels harder than it ever did with my polar meter (and my NP #'s are lower for SRM based on a few equal perceived exertion rides), yet it is reporting higher power #'s at the upper end, and lower at the low end? 😕

    So either:
    1) I got stronger in fat burning mode (not likely)
    2) The Polar dumped high numbers giving low 5s power outputs
    3) My SRM has a problem where it amplifies high torque values

    What do you think? Oh and yes I correctly entered the slope, and zero it out often... no I have never checked the factory reported slope.

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  2. JTE83
    Archived post
    #2

    You have the SRM & Polar on the same bike? Maybe you can do a comparison report if you like.

    I'm very surprised how few Polar users there are from my poll. And I guess Polar won't get a few more cuz it seems like their new CS600 PM isn't good enough.

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  3. ric_stern/RST
    Archived post
    #3

    your 5-sec numbers are potentially possible.

    on the other hand have you calibrated your SRM? (i don't mean zeroed it, i mean calibrated it)

    ric

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  4. wilmar13
    Archived post
    #4
    JTE83 said:

    You have the SRM & Polar on the same bike? Maybe you can do a comparison report if you like.


    If I was smart I would have done that... but I was too excited to install my new toy so I took off the Polar a day before the SRM was scheduled to arrive (I sold it to a freind)... Man people whine about the wires and sensors of the SRM, but it looks so clean compared to the mass of wires and sensors the Polar required.

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  5. wilmar13
    Archived post
    #5
    ric_stern/RST said:

    your 5-sec numbers are potentially possible.


    Yeah I also thought of something this morning... I was comparing my 5 sec #'s as calculated by cycling peaks... but if you are only collecting the data every 5 seconds, and the polar is giving rolling 5 sec averages... you can end up with a reported 5 s P that is closer to 10s(2 data points)... and my 10s power with SRM is in line with Polar based on perceived exertion. Besides with 36' inseam and 180mm cranks I can probably create a high initial torque load in spite of my avg fast twitch ability giving high instantaneous power at high cadences.

    No haven't calibrated it, but after a hard hammerfest today where I got some good data launching off the front I may need to move my FTP down somewhere around 20 watts with the SRM. :o Of course it is only January and on the bright side my 1 minute power is still what I thought it should be... 😉

    Besides I don't really care if the #'s are off by x% as long as it is consistent since you don't race power meters...I think I was shocked to see #'s that high, but in reality making big watts for 1-2 sec is meaningless anyhow.

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  6. bikeguy
    Archived post
    #6
    wilmar13 said:

    For example today I jumped into the draft of a passing minivan producing a 5 second avg of 1183 watts (1645, 1562, 1023, 978, 707) . Is this real or is were the first 2 seconds garbage? I mean a 5 sec avg this high with my Polar would have been pretty hard... not that it was easy today but I didn't need to dig deep into my suitcase of courage or anything. If I throw out the two high numbers and do more like 1000 watts it results in 5 sec power of ~950 watts, which seemed more like the effort based on my Polar experience.

    The polar is not good at picking up peak power while an SRM should be. As for your 5 sec power, a power of 1280 watts for 30 sec was the average measured for US elite national class sprinters, some time in the 1980's, I don't remember exactly now.

    -bikeguy

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  7. bikeguy
    Archived post
    #7

    The exact data:

    Garret & Kirkendall, Exercise & Sports Science, Lipincott Williams & Wilkins

    I think this for sometime in the 80's, Male Track National Team:

    The exact data 10 sec wingate: 1779 w pk, 1504 w avg
    30 sec wingate: 1730 w pk, 1258 w avg

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