Initial PowerTap settings

Discussion in 'Power Training' started by MikeMuk, Aug 26, 2006.

  1. MikeMuk

    MikeMuk New Member

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    Hey guys,

    Just got my powertap and have done my first ride on it and wanted to pick your brains.

    1) The number seem a bit too high. It was an easy ride (with a sprint thrown in) and I averaged 184W for an average speed of 17.5mph (on flat terrain).
    2) Along with the high numbers, during my sprint it reckons my max wattage was 1182W - and I certainly don't see myself as a sprinter in any way, shape or form.

    So, here's how it's currently set up:-
    *Doesn't use zero's in the average for speed or cadence, but does for wattage,
    *All values are displayed on 2 second rolling average,
    *I have a sharkfin sensor, which is mounted on the chainstay with the "blob" on the inside
    *It's mounted to a Specialized Roubaix comp (so all carbon with very "swoopy" seat and chainstays)

    I weigh around 80kg and am 186cm tall.

    On top of this, it doesn't want to download (although I think it's the fault of the drivers). I've installed powertuned, supposedly installed the drivers for it (first the ones on the CD, then went onto the website mentioned in the documentation) and when I put the head unit in the cradle, the software says it can't find it. The unit is properly fitted into the cradle and I am using the correct COM port.

    Know this sounds a bit sketchy, but something doesn't feel quite right to me. If anyone has any good tips for inital setup and any thoughts then I'd really appreicate it.

    Mike
     
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  2. RapDaddyo

    RapDaddyo Active Member

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    Did you zero the torque before the ride? The owner's manual should tell you how to do it.
     
  3. MikeMuk

    MikeMuk New Member

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    Yeah, just realised that I should have possibly done that! D'oh! ow to try and get the damned thing to download to my computer...
     
  4. RapDaddyo

    RapDaddyo Active Member

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    I never use the software that came with my PT. Never took it out of the sleeve. I use CyclingPeaks exclusively. Just snap the PT computer in the cradle, turn it on, get "Host" on the display and download the ride file into CP.
     
  5. tanggoman

    tanggoman New Member

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    I never used the software that came with it and used cyclingpeaks trial version and will be buying the full very soon. You know when the torque is set correctly is when your coasting, the reading on the WATTS (not average or max) is 0.
     
  6. postal_bag

    postal_bag New Member

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    Coincidentally, today I went for my usual group ride for the first time with my new powertap and got exactly the same averages as you. The average speed for the 4 hours was 28.1 km/h (17.45 mph) and the average power was 184w on flat and rolling terrain. I did not sprint, but in at one point I hit 1055w.
    The amazing thing to me was the 30 min stretch where I averaged 300w while riding in a group of 75 people.
     
  7. MikeMuk

    MikeMuk New Member

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    Yeah, I figured that the wattage should read zero when coasting, which it does, there's just something about the numbers I don't quite like, it also seems to take it a short while to reduce to zero - take a moment to decay - is this normally the case? I've got it on two second rolling avaerage, so maybe it's refreshing to often and surprising with large numbers. What does everyone have it set to.

    Also, what is the general consensus about mounting the reciever on the chainstay of a CF bike? Ok with a bit of rubber underneath it? With the shark fin, which way should it face (logo facing the wheel or not and the longer edge nearer the hub or BB)? It's fair to say the manual isn't too clear about these things.

    Mike
     
  8. Thorman

    Thorman New Member

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    Keep in mind just because you see zero watts while coasting doesn't necessarily mean your torque is zero. The only way to actually ensure this is to switch over to torque mode and see zero torque while coasting. Your owner's manual will tell you how to do this.
     
  9. Alex Simmons

    Alex Simmons Member

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    You're not, at least not yet;). Your 5 sec power will be less than 1 sec peak by say 50-100 W, so estimating your 5 sec power as , say 1100W, for an 80kg man = 13.75 w/kg. That indicates your neuromuscular power is in the middle of a Cat 5 racer range. Maybe do a few flat out efforts when fresh to see what you can really do.
     
  10. jws

    jws New Member

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    the numbers sound reasonable to me....

    a couple of suggestions:

    don't bother with powertuned at all; uninstall it and get CPS.

    experiment with different rolling averages until you find what you like; i keep mine at the lowest; the other settings are still jumpy, but just less current.

    i may be wrong, but using no zeros for speed and cadence doesn't really make sense, at least the way the manual describes it, i.e., "averages them only when pedaling".
     
  11. grv

    grv New Member

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    It will take as many seconds to "decay" as seconds you have for rolling average. I have mine set to 3 secs. Not to concerned about short peaks when riding, just with staying in zones. The jumpier the display, they harder it is for me to regulate my power. The averaging of data displayed on the PT computer while riding doesn't affect what it records, so I can nit pick and look for peaks in CP after the ride...
     
  12. MikeMuk

    MikeMuk New Member

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    As far as my understanding goes, it you don't have the zeros included in the speed averaging then the unit works with a sense of auto start and stop. Could be way off the mark though!

    Been out with it again, and I guess I'm just not used to seeing the numbers. I'll be riding along (the terrain near me is a little bumpy) and my PE doesn't really change, but I'll see the wattage jump from 200 - 400 and then back down again quickly. Even changing the rolling average to a longer one doesn't seem to affect this characteristic...

    If anyone's willing, it'd be a help for someone to have a look at one of my files and see if it "looks" right - being a newbie it's a tad tricky to know that kinda thing.

    Mike
     
  13. jws

    jws New Member

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    the numbers will always be jumpy, even if you set the rolling avg to 30sec!! that's the nature of power. at first, you'll mostly need to look at averages over time to get any meaning out of the numbers. that means either using good software to analyze after the ride, or using the interval function and looking at the average power.

    you'll learn with experience to interpret the display, but also to not over-interpret it.

    as far as how the avg speed and cadence are calculated, you may be right. i'm only going by what the manual says. i'll test it out and see.
     
  14. jws

    jws New Member

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  15. RapDaddyo

    RapDaddyo Active Member

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    Because that's the nature of torque. The strain gauges are very, very sensitive inside the hub. They pick up the slightest change in the force you are applying to the cranks. That's why I manage power with cadence. If I tried to maintain a constant power, I would be "chasing" watts all day, constantly over-correcting. Instead, I choose a gear and get into my preferred cadence, check the PM during a few revolutions and then adjust cadence or (if necessary) change gears until I get the power I want. Then, until the grade or wind changes, I ride a constant cadence and spot-check the PM from time to time.
     
  16. Alex Simmons

    Alex Simmons Member

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    Or this site which has all the links in one spot....
    http://www.trainwithpower.net/
     
  17. mickthomas

    mickthomas New Member

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    Are you sure about that ? The power value (W or Nm/s) is derived from torque (Nm) so if power is zero how could the torque be anything other than zero?
     
  18. RapDaddyo

    RapDaddyo Active Member

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    IIRC, torque can atually be negative when coasting but the display (watts or torque, I can't recall if it's both or just watts) doesn't display negative numbers. So, watts=zero is a necessary indicator that torque has been zeroed but not a sufficient indicator.
     
  19. Macey

    Macey New Member

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    My $0.02 worth - the numbers look fine Mike. You get more of a feel for the wattage once you've been riding with the meter, but it is suprising how quickly your wattage will increase (with little change in perceived effort) when you hit even a slight incline. And the reason that the wattage jumps around is that your power output will be jumping around. Don't let it phase you - that's just the way it works.

    The average and sprint peak numbers look close to what I would expect for someone on an easy ride. Although the peak is good for a first attempt - I almost stacked it on my first sprint with the meter trying to read the display while sprinting and avoiding parked cars. :)
     
  20. Bike N Ski

    Bike N Ski New Member

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    On my last ride I did a 30 sec sprint where max. watts read 1396 on the display. However, in cycling peaks software my max. watts recorded for the entire ride was only 941. Is it a case that the higher reading wasn't stored or sampled as a datum point in the file but only maintained as my peak wattage in the max watt display field on the power tap? Or should this downloaded max. watts match the display? Thanks in advance for any comments.
     
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