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SRM calibration

  • 07-03-2013 10:31am
    #1
    amjon.
    Registered Users, Registered Users 2 Posts: 403 ✭✭


    Can anyone help with the following:

    When calibrating the SRM the following step is confusing me -
    Calculate the torque you get when the weight hangs on the horizontal pedal crank.

    If the crank is horizontal then when you put the weight on it won't it get pulled down to vertical or do you have to hold the opposite crank in place then take the reading?


Comments

  • #2
    Raam
    Registered Users, Registered Users 2 Posts: 14,318 ✭✭✭✭Raam


    Hold the bike in place on the ground and hang it off the crank which is pointing forward?


  • #3
    Lumen
    Registered Users, Registered Users 2 Posts: 31,218 ✭✭✭✭Lumen


    Roll your bike backwards, then roll it forward.


  • #4
    amjon.
    Registered Users, Registered Users 2 Posts: 403 ✭✭amjon.


    Turns out I need to stick in a trainer and keep the break on with a cable or tape.


  • #5
    doozerie
    Registered Users, Registered Users 2 Posts: 4,830 ✭✭✭doozerie


    amjon. wrote: »
    Turns out I need to stick in a trainer and keep the break on with a cable or tape.

    Surely it'd be easier to do what Raam suggested? Assuming you have a chain fitted then the (leading) crank won't get pulled down to vertical unless you let it rotate the rear wheel, which won't happen if you are holding the bike stationary.


  • #6
    spyderski
    Registered Users, Registered Users 2 Posts: 1,270 ✭✭✭spyderski


    What SRM do you have? I believe the old wired ones needed more fiddling/calibration, but with mine (DA7900) I originally set the slope on my Garmin, then zero the offset before every ride (apparently even this is not strictly necessary). AFAIK the recalibration with a weight only needs to be done when the battery is changed, this is usually done at the SRM Service centre.


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  • #7
    morana
    Registered Users, Registered Users 2 Posts: 2,099 ✭✭✭morana


    spyderski wrote: »
    What SRM do you have? I believe the old wired ones needed more fiddling/calibration, but with mine (DA7900) I originally set the slope on my Garmin, then zero the offset before every ride (apparently even this is not strictly necessary). AFAIK the recalibration with a weight only needs to be done when the battery is changed, this is usually done at the SRM Service centre.

    When I was serious i would do it evry month and it was stable enough but definitely after a battery change.

    Once you do it once its simple


  • #8
    amjon.
    Registered Users, Registered Users 2 Posts: 403 ✭✭amjon.


    spyderski wrote: »
    What SRM do you have? I believe the old wired ones needed more fiddling/calibration, but with mine (DA7900) I originally set the slope on my Garmin, then zero the offset before every ride (apparently even this is not strictly necessary). AFAIK the recalibration with a weight only needs to be done when the battery is changed, this is usually done at the SRM Service centre.

    Have a couple wired ones, pro and DA 7800. I'd love to get a wireless Rotor one but I just can't justify it. I think the new ones auto zero the off-set.
    morana wrote: »
    When I was serious i would do it evry month and it was stable enough but definitely after a battery change.

    Once you do it once its simple

    Yes, it's grand now. Hardest part was lugging the weight to the post office to have it weighed.

    How may weights did you use when you calibrated it?


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