Power to ride a 56 min. 40k TT

Discussion in 'Power Training' started by veloguy, Aug 21, 2003.

  1. veloguy

    veloguy New Member

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    I just found this forum and thought I would contribute. Many of you wonder how much power it takes to ride at certain speeds. Of course the natural disclaimer is that it is impossible to tell because of differing frontal areas, equipment choice, course profile, weather conditions, etc. But I thought I would share my info anyway.
    Last Sunday was the Oregon State TT Championships. The course was a flat, fast, accurate, out and back, 40k. There was blue sky, temp in the 70's. However, there was a wind out of the north on this north/south course. So, you had a tailwind out/headwind back situation.
    I am 6'0" and 171 lbs and 38 years old. My bike is an old Softride Power V, Visiontech bars, an old 8 spoke Spinergy in front, disc in the rear, skinsuit and aero helmet. Basically, a pretty aero setup. FWIW, if you go to Analytic Cycling, I have determined from my database of rides that I have a frontal area of .60.
    I decided to ride conservative going out so that I had enough power coming back against the wind. I hit the 20k turnaround in about 26:40 or 27.9mph. Coming back, I put more effort into it and had a split of about 30:30 or 24.4mph. Total time was 57:15 or 26.0 mph.
    Without the wind I would have been deep into the 56's. I wasn't able to ride with my Powertap, but referring to my extensive database of TT's, I would of averaged right at 350 watts. I also have a max HR of about 182 and I averaged 166 for the TT or 91% of max. If I would have gone out harder, I would have averaged 167-168 or about 92%. So, I was slightly into the anaerobic range or, put another way, I was just above my anaerobic threshold. Hope this helps, Kevin
     
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  2. v02max

    v02max New Member

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    What is "frontal"? What does it tell you and how do you
    figure it?

    Thanks!

    __o
    == \ <
    ( ) / ( )
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  3. veloguy

    veloguy New Member

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    Any object moving thru air or water has a frontal area. An semi truck has a greater frontal area than your passenger car. You have a greater frontal area when you ride on the tops of your handlebars than when you are on the aero bars. That's why we use aero bars, to reduce our frontal area. The only way to measure you own frontal area is to book time in a wind tunnel. However, if you have a powermeter, you can figure it out fairly close by determining how many watts it takes to ride at certain speeds in various riding positions. It really only matters if you are trying to use one of the cycling calculators on the internet. Analytic Cycling is the best, IMO. Without plugging in that info you won't get accurate results. As I said, on my TT bike, my frontal area is around .60. On my road bike on the brake hoods, it is about .72. Let me know if that helps, Kevin

     
  4. RPLewis

    RPLewis New Member

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    Thanks Veloguy for sharing your information.

    Perhaps you would like to enlighten the others on this list the training required to be able to generate 350w for an hour or 4.5w/Kg or 2.04w/lb (These are probably a better measure of performance as lighter riders will not have to produce as much power to achieve the same speed due to smaller frontal area values and effects of hills etc).

    TIA

    R.
     
  5. ric_stern/RST

    ric_stern/RST New Member

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    For general racing (i.e., non hill climbs) it's better to scale power allometrically as mass^0.67.

    Got to train hard to get that sort of power, or be quite large, or have chosen your parents well!

    Ric
     
  6. RPLewis

    RPLewis New Member

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    Ric, I don't understand the quite large statement...if power is scaled to mass^0.67. ?

    Hence comparsions of Watts/Kg is a better measure than a pure wattage number alone. As per VO2Max in ml/kg/min. rather than ltrs/min.

    R.
     
  7. ric_stern/RST

    ric_stern/RST New Member

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    i just mentioned the "quite large" bit because you mentioned an absolute power (350 W) rather than one that was relative to something. although, on re reading your post i see you did also mention relative powers. opps!

    wonders what time he wrote the message...? maybe it was just after finishing my turbo session...

    Ric
     
  8. J-Law

    J-Law New Member

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    What kind of a power meter do you use. Your estimate of 350 w seems a bit high to me. I did a time this yr at our state TT within a few seconds of you and I did race w/ my PT. My avg was 306 w and I am a lot bigger than you, plus I weigh in at 87 kg which means I need to produce more power to generate the same speed. (I have calculated a frontal area on Analyticcycling.com of about .65 and a CdA of about .36.

    I would have guessed you would only need an avg of about 280w to turn a 57.

    Either way that is a great time :)
     
  9. veloguy

    veloguy New Member

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    J-Law, I use a Powertap, like you. I think where the Analytic Cycling estimates you come up with vs. mine in in the Cda of .36. On the site it says "use default value" of .5. I never change that. Like you I have been able to figure out my frontal area based upon dozens of TT's and many training rides. I use .60 as my frontal area and it is very accurate. I do a 10 mile TT every Thursday night put on by a local cycling club. I ride between 22:30 and 23:00 consistently. this is 26-26.6mph average, the same as I did in the 40k. I am always in the 340 watts range. I have read numerous times that 2 cyclist riding side by side will generate different readings. Also you have to take into account cycling efficiency. I have only been cycling a short time, maybe I pedal squares. You might be able to ride the same speed as me at less watts, or faster at the same watts. Or maybe we don't have our P/T's calibrated the same. How many mm's do you have inputted for you tires roll out? There are many variables. Kevin

     
  10. ric_stern/RST

    ric_stern/RST New Member

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    Originally posted by veloguy, i replied with >>

    J-Law, I use a Powertap, like you. I think where the Analytic Cycling estimates you come up with vs. mine in in the Cda of .36. On the site it says "use default value" of .5. I never change that. Like you I have been able to figure out my frontal area based upon dozens of TT's and many training rides. I use .60 as my frontal area and it is very accurate.

    >>On the page (e.g., power given speed), you have two (possible) variables to input at the top of the page: effective frontal area and drag coefficient. These are used to produce (i.e., multiplied together) CdA. Thus it doesn't matter which one you alter or both of them.

    >>also, if you're trying to calculate CdA from this page, it's *imperative* that you know the grade of the road(s), wind speed and direction, and air density, as these will affect the results.


    I do a 10 mile TT every Thursday night put on by a local cycling club. I ride between 22:30 and 23:00 consistently. this is 26-26.6mph average, the same as I did in the 40k. I am always in the 340 watts range. I have read numerous times that 2 cyclist riding side by side will generate different readings.

    >>two cyclists riding the same road at the same time might well generate different power outputs. This will be due to different CdA's, equipment, mass, and also whether you had a sidewind hitting one ride more than the other.

    Also you have to take into account cycling efficiency. I have only been cycling a short time, maybe I pedal squares.

    >>efficiency won't affect power output or speed, but *may* affect the metabolic cost (i.e., someone who is less efficient will expend more energy at the same power output). However, efficiency is virtually the same for all cyclists. This is because when cycling we are constrained by the pedals, so there can be only very slight differences in the way that we pedal.

    >>everyone pedals circles unless there's something seriously wrong with your cranks/pedals.


    You might be able to ride the same speed as me at less watts, or faster at the same watts.

    >>this would only be due to differences in CdA (flat roads) or mass (hilly roads) or a combination of the two. i'm assuming that topographical and environmental conditions are the same for both rides.

    Or maybe we don't have our P/T's calibrated the same.
    >>as long as the PT reads zero when freewheeling (i.e., torque hasn't drifted) then the PT *is* calibrated (unless the torque tube fails, in which case you'll either get zero watts when pedalling or some daft figure like riding steady at 2000 W)


    How many mm's do you have inputted for you tires roll out? There are many variables.

    >>this makes no difference to the power that is displayed whatsoever, but would obviously affect the speed display (however, if you were/are comparing a TT over set course you;d go by time!).

    Ric


    Kevin [/QUOTE]
     
  11. Frank Gaster

    Frank Gaster New Member

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    Would you type "27.9 mph" on Google and find my question, which is can anyone ride an unmodified 32 lb Schwinn 10 speed 30 mph. :confused:
     
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