Ergomo Calibration using PT

Discussion in 'Power Training' started by Geoff2010, Feb 7, 2007.

  1. Geoff2010

    Geoff2010 New Member

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    I have been having some troubles with a new Ergomo unit. When I first rode the bike the power was WAY off, it was very obvious... 250W (estimated) was reading 300W.

    I convinced a buddy to let me use his PT to try and calibrate the unit. The factory suggested k-factor is 182, I had to drop it all the way down to 165 to have it match the PT. The PT and Ergomo line up pretty nicely until I get into the higher power (+300W), then there is some drift with the Ergomo reading lower than the PT. the drift isn't linear, it appears to get worse as the power is increased.

    My question is two part:

    1 - The LBS who installed the unit admitted today that they did not use a torque wrench to install the BB. They did, however, chase/re-face the shell before installation. They also have the wires exiting at exactly 9 o'clock. Could the fact that the unit may not have been torqued properly cause this type of mis-reading?

    2 - Are there other variables that could affect the Ergomo to the point that the mounted k-factor is almost 20 points off the factory specified?

    I am taking the bike back to the LBS next week to have it removed and re-installed. Any suggestions on what I should tell them aside from the documented install instructions?

    Thanks,
    Geoff
     
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  2. JungleBiker

    JungleBiker New Member

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    Hi Geoff,

    I am curious to know why you think the Ergomo was reading too high at 300W? Where did you get the 250W idea from?

    I think you should stick to the original k-factor. I also don't think the torquing is an issue. Rather I wonder if it is due to the Ergomo measuring power at the BB and the PT measuring power further downstream at the rear hub (with power being lost in the chain system)? I think it's more important to measure your power with the Ergomo and train based on those power measurements rather than to try get your Ergomo to give the same readings as a PT.

    Just my thoughts, others may have a better idea.

    JB.
     
  3. Geoff2010

    Geoff2010 New Member

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    JB,
    I had both the Ergomo and the PT mounted on my bike simultaneously. AFAIK, problems with the Ergomo install can cause all kinds of issues... hence the calibration process using PT.

    I know for a fact that when using the factory specified k-factor the unit is wrong. Unless I can ride with Floyd Landis, there is no way it could be accurate... at least 50-75W higher then it should be.

    I got the 250W estimation based on the fact that I have been training with power for over a year, so I know what various efforts "feel" like. My major issue at this point is the apparent non-linear readings I am getting from the unit. It is pretty close to the PT until 300+W then it falls off.

    Over/Under torqueing the unit at install couldn't have this affect on the power readings?

    Thanks,
    Geoff
     
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