PowerTap Pro Cadence

Discussion in 'Power Training' started by BtonRider, Apr 24, 2008.

  1. BtonRider

    BtonRider New Member

    Joined:
    Jan 30, 2006
    Messages:
    114
    Likes Received:
    0
    I just purchased the PowerTap a month ago and I've been using the additional Cadence sensor. I noticed it has a built in feature where it analyzes the pulsations in the hub to determine the cadence. Has anyone used the built in feature before? I'm wondering how reliable it is. I wouldn't mind shaving off a few extra grams from the total weight of the PowerTap set up, but only if I can trust the numbers.
     
    Tags:


  2. daveryanwyoming

    daveryanwyoming Well-Known Member

    Joined:
    Oct 3, 2006
    Messages:
    3,857
    Likes Received:
    97
    When I built up a new road bike last fall I didn't bother mounting the optional PT cadence sensor and have been running it on derived hub cadence ever since. My TT bike and older road bike both use the crank based cadence sensor. The values from both systems seem accurate, hard to know for sure as you measure one or the other at a given time but I don't get cadence drop outs or unrealistic high or low cadence values. Hub based cadence might be a bit jumpier when I look at downloaded files in WKO+ but I use a bit of display averaging and it all seems fine. I guess the related question is how much accuracy do you really need in cadence readings? Will you alter your training or racing if a particular section showed 88 rpm when you really wanted 90 rpm?

    -Dave
     
  3. strader

    strader New Member

    Joined:
    Jun 28, 2007
    Messages:
    195
    Likes Received:
    0
    I tried using the calculated cadence and found it very inaccurate. When pedalling at 110+ rpms it would report about half that (~60rpms).
     
  4. BtonRider

    BtonRider New Member

    Joined:
    Jan 30, 2006
    Messages:
    114
    Likes Received:
    0
    True enough. I would just like to be sure it's not off by 20rpm.
     
  5. BtonRider

    BtonRider New Member

    Joined:
    Jan 30, 2006
    Messages:
    114
    Likes Received:
    0
    Yikes! Was it more reasonable at lower cadence?
     
  6. flanman

    flanman New Member

    Joined:
    Mar 13, 2008
    Messages:
    15
    Likes Received:
    0
    The hub-based cadence works ok, with a few flaws.

    It cannot read above about 140 rpm. Don't trust any readings above 120 rpm. This isn't a big issue, but if you're training for track or sprinting then it's better to use the cadence sensor.

    rpm for one legged pedalling will be off.

    Due, I think, to aliasing, there are some values that it never reads. For instance, it may read 93 or 95 rpm but never 94. There are data holes every 12 rpm or so. This is a minor inconvenience. Set cadence averaging to 3 or 5 seconds and you'll never notice it.

    In short, hub cadence sensing is usally good enough for most riders' needs. Be aware of its limitations though.
     
  7. RChung

    RChung New Member

    Joined:
    Sep 12, 2006
    Messages:
    306
    Likes Received:
    1
    Depends on what you want to do with the cadence numbers but for most purposes it's a red herring. You have a power meter. Focus on power.
     
  8. strader

    strader New Member

    Joined:
    Jun 28, 2007
    Messages:
    195
    Likes Received:
    0
    Yeah, it seemed fine at low cadences. I think for anything higher than ~95 rpm it would read only half the pedal strokes.
     
Loading...
Loading...