Power accuracy in the cold

slowbike
slowbike Posts: 8,498
edited December 2019 in Indoor training and turbo forum
Our turbo lives outside - well, outside our heated home anyway - it's location is weatherproof, but obviously not heated.
I had a quick spin last night - just a leg stretcher tbh, but boy, it was hard work - ok, it was <3° outside, so I didn't need a fan and I expected it to take a little while for me to warm up, but I was struggling to hit a sustained 100w - now, I know I'm "slow", but I'm not that slow - even my slowest TTs are over double that power - recorded on a Stages PM that has previously agreed to the power shown on my turbo ...

I intend to pop the power meter on the turbo bike and check the two agree - but what's your thoughts? Should it read lower when it's cold? Should I warm up the turbo with a fan heater?

Comments

  • wongataa
    wongataa Posts: 1,001
    What type of turbo is it?
  • slowbike
    slowbike Posts: 8,498
    Bkool Smart Go
  • whyamihere
    whyamihere Posts: 7,717
    Have you done a spin down/calibration on it in the colder weather? Power meters can be susceptible to changing temperatures, which is why active temperature compensation is a selling point for them.
  • wongataa
    wongataa Posts: 1,001
    You should be performing a calibration routine on any wheel on trainer once it has warmed up to give it a fighting chance of spitting out vaguely correct numbers.
  • slowbike
    slowbike Posts: 8,498
    There is no calibration tool for the Bkool ...
  • chris_bass
    chris_bass Posts: 4,913
    I know DC rainmaker mentioned about having to do spin downs when there is a big drop in temperature and it can make as much as a 5 or 10% difference if it is much colder.

    I know the bkool doesn't have a calibration option so it must take temperature into account somehow. Did it get easier after 10 to 15 minutes? as it is a wheel on trainer it should get hotter as you use it.
    www.conjunctivitis.com - a site for sore eyes
  • chris_bass
    chris_bass Posts: 4,913
    I found the quote from DC Rainmaker

    "In general, you should calibrate every once in a while (perhaps every few weeks), or anytime you’ve moved the trainer some distance (like to a new home/etc…). Additionally, you should calibrate if you’ve had a major temp swing (such as if it lives in your garage and now the sweat puddle on the floor is frozen). In my testing – I found it legit did make a difference in temp shifts (about 20w difference on 220w from my ride on Saturday)."
    www.conjunctivitis.com - a site for sore eyes
  • wongataa
    wongataa Posts: 1,001
    With wheel on trainers the tyre pressure makes difference too.
  • slowbike
    slowbike Posts: 8,498
    Thanks - yer - I rekon it's reading low

    I pumped the tyre(s) up - the front has a puncture - it used to be slow - it's now hissing out - I don't think that makes a difference! ;) but the back is up to pressure and it has a turbo tyre on it.

    I think it was a little easier after 10-15 minutes, but TBH I'd been working hard up till that point.
    There is no calibration to do - the software doesn't have any option for it.

    TBH, it doesn't really matter - I just recalibrate my expectations and work off HR data and/or perceived effort

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