SRM slope

Discussion in 'Power Training' started by Zach-dk, Mar 24, 2007.

  1. Zach-dk

    Zach-dk New Member

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    What changes SRM slope?
    I have a SRM Pro. The old slope was 20,42 Hz. I moved it to my
    summerbike two days ago and made a calibration today that gives a new
    slope at 16,39 Hz. That´s a diffenrence of 18,59%
    Before mounting the SRM on the new bike I changed the decal (meaning I
    removed the crank and mounted it again) and mounted new chainrings.
    Can all this cause the change?
    The ride I did yesterday was just a recoveryride with two small
    sprints to bed the cranks before making the calibration today. The
    ride yesterday was done with the old numbers entered in the SRM, and
    gave me lower readings than I expected. When I change the slope
    setting in the SRM file properties the numbers look more those I
    usually get.

    Zach
     
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  2. evanhyde

    evanhyde New Member

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    General use over time causes the slope to drift. I don't think that any changes in chainrings or bikes causes the slope to change, just using the power meter leads to a slow drift. That is why SRM recommends sending it back to them once per year for recalibration. I did so after 18 months of use and my slope was very different. It can be frustrating because all of the rides leading up to recalibration were giving power readings much higher than they should have been.

    How are you calibrating your SRM? It would be very useful to be able to recalibrate at home more often, not to mention the cost savings of not having to send it back every year. Are you just applying a known torque and comparing it to the torque readings?
     
  3. Zach-dk

    Zach-dk New Member

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    I use a 20 kg weight (or exactly 19,65 kg) and follow the precidure recommended by SRM and put in the number in spreadsheet.

    Since my first post I have done a check every day and the numbers are about the same every time. On my trainingrides the numbers match what I expect - both on 20 minutes interval and all out sprints. If anything they are a little lower than expected :confused:
     
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