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Powertap reading low!

hopper1hopper1 Posts: 4,389
It appears my PT is not showing realistic Watts...
I use it in conjunction with a Garmin 705, so calibration is done differently, and also there is no selection to calibrate in torque, by hanging the known weight off the pedal.
Are there any other tests I can carry out using the Garmin, or do I need to send the wheel away?
If I need to send it away, where should it go?

Thanks in advance, for any help.
Start with a budget, finish with a mortgage!
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  • AnonymousAnonymous Posts: 79,667
    hopper1 wrote:
    It appears my PT is not showing realistic Watts...
    I use it in conjunction with a Garmin 705, so calibration is done differently, and also there is no selection to calibrate in torque, by hanging the known weight off the pedal.
    Are there any other tests I can carry out using the Garmin, or do I need to send the wheel away?
    If I need to send it away, where should it go?

    Thanks in advance, for any help.

    I've been thinking that with my Garmin compared to the little yellow effort. I've put it down to me being really weak!
  • hopper1hopper1 Posts: 4,389
    Hmmm, but I don't know any one with a PT, let alone the 'little yellow effort'!...
    I don't fancy spunking £165 on a CPU, just for a cross reference :shock:
    Start with a budget, finish with a mortgage!
  • AnonymousAnonymous Posts: 79,667
    hopper1 wrote:
    Hmmm, but I don't know any one with a PT, let alone the 'little yellow effort'!...
    I don't fancy spunking £165 on a CPU, just for a cross reference :shock:

    Try going to 'settings'
    'ANT+'
    'Calibrate Powermeter'
    Spin the pedals, then let it spin, it should be zero when coasting, press calibrate again when no effort is being applied and you should be right...
  • BronzieBronzie Posts: 4,927
    I don't think you can check the calibration with a Garmin as you can't read the raw torque value so you can't do a "stomp test". If you bought the unit from Cyclepowermeters, Bob Tobin may lend you a Powertap head unit to check the calibration.
  • hopper1hopper1 Posts: 4,389
    Cheers, Alex.
    I'll try that when I get home...
    I did try a similar operation last week (but was coasting on the road), but it just wouldn't calibrate until I stopped!
    I take this would be done in the workstand, or holding the rear up in the air. Then get the rear wheel spinning and hit 'calibrate' whilst it's still spinning?

    Fcuking technology...

    It's expensive equipment to be using the HR as a back up!
    Start with a budget, finish with a mortgage!
  • AnonymousAnonymous Posts: 79,667
    hopper1 wrote:
    Cheers, Alex.
    I'll try that when I get home...
    I did try a similar operation last week (but was coasting on the road), but it just wouldn't calibrate until I stopped!
    I take this would be done in the workstand, or holding the rear up in the air. Then get the rear wheel spinning and hit 'calibrate' whilst it's still spinning?

    Fcuking technology...

    It's expensive equipment to be using the HR as a back up!

    Yes, I do mine in the turbo...
  • hopper1hopper1 Posts: 4,389
    Bronzie wrote:
    I don't think you can check the calibration with a Garmin as you can't read the raw torque value so you can't do a "stomp test". If you bought the unit from Cyclepowermeters, Bob Tobin may lend you a Powertap head unit to check the calibration.

    I got it through wheelsmiths as a handbuild...
    Start with a budget, finish with a mortgage!
  • jibberjimjibberjim Posts: 2,810
    You can also use an ANT+ dongle and some code on a computer to do it, there's no actual need for the LYC, so then you're only looking at 20quid or so for a dongle.

    see http://jibbering.com/blog/?p=527
    Jibbering Sports Stuff: http://jibbering.com/sports/
  • PokerfacePokerface Posts: 7,960
    I was wondering the same thing - just got a Garmin 500 and the wattages seemed low compared to what I was doing on my Yellow head unit. Will take both out on the next ride and compare the figures.
  • AnonymousAnonymous Posts: 79,667
    I don't mind my readings being low, I just hope they are consistent!
  • redddraggonredddraggon Posts: 10,862
    Instantaneous wattage? Or average wattage? What are you finding low?

    There is a feature called "Smart Recording" which is probably best turned off when using with a powermeter.
    I like bikes...

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  • hopper1hopper1 Posts: 4,389
    Pokerface wrote:
    I was wondering the same thing - just got a Garmin 500 and the wattages seemed low compared to what I was doing on my Yellow head unit. Will take both out on the next ride and compare the figures.

    You can't add them together, though... To imrove your w/kgs... :wink:
    Start with a budget, finish with a mortgage!
  • hopper1hopper1 Posts: 4,389
    jibberjim wrote:
    You can also use an ANT+ dongle and some code on a computer to do it, there's no actual need for the LYC, so then you're only looking at 20quid or so for a dongle.

    see http://jibbering.com/blog/?p=527

    Is this available from Garmin, or elsewhere...
    Start with a budget, finish with a mortgage!
  • AnonymousAnonymous Posts: 79,667
    Instantaneous wattage? Or average wattage? What are you finding low?

    There is a feature called "Smart Recording" which is probably best turned off when using with a powermeter.

    SR defo turned off (otherwise the average readings would be high as it would discount the zeros?)

    I'm not sure if mine is low, I just seemed to get suddenly weaker when I got my garmin!
  • AnonymousAnonymous Posts: 79,667
    A couple of suggestions here...

    https://forums.garmin.com/showthread.php?t=1068
  • amaferangaamaferanga Posts: 6,789
    Calibration should be done when stopped, hence why it doesn't work when you're moving.

    I'm surprised that people are thinking their Garmin reads low as I've only heard claims of over-reading Garmin's (compared to the LYC).

    I use a 310XT and I've seen nothing to suggest it's not consistent (though I don't know if it reads high or low as I don't have a LYC).
    More problems but still living....
  • jibberjimjibberjim Posts: 2,810
    hopper1 wrote:
    jibberjim wrote:
    You can also use an ANT+ dongle and some code on a computer to do it, there's no actual need for the LYC, so then you're only looking at 20quid or so for a dongle.

    see http://jibbering.com/blog/?p=527

    Is this available from Garmin, or elsewhere...

    Ant Sport Dongles are available all over the place, lots on ebay.
    Jibbering Sports Stuff: http://jibbering.com/sports/
  • hopper1hopper1 Posts: 4,389
    jibberjim wrote:
    hopper1 wrote:
    jibberjim wrote:
    You can also use an ANT+ dongle and some code on a computer to do it, there's no actual need for the LYC, so then you're only looking at 20quid or so for a dongle.

    see http://jibbering.com/blog/?p=527

    Is this available from Garmin, or elsewhere...

    Ant Sport Dongles are available all over the place, lots on ebay.

    Plenty of dongles, cheers Jim. :wink:
    The dongles only seem to mention Forerunner 50, or 405's, is there a specific model for the 705, or are the all generic fit?
    Sorry for the dumb questions like, but my work internet access is slow and this is painful...

    Now I've been to ebay, I'm bidding on something else, too...! :roll:
    Start with a budget, finish with a mortgage!
  • jibberjimjibberjim Posts: 2,810
    hopper1 wrote:
    Plenty of dongles, cheers Jim. :wink:
    The dongles only seem to mention Forerunner 50, or 405's, is there a specific model for the 705, or are the all generic fit?

    They're for your PC, they won't talk to the 705, you use the PC and the dongle to talk to the powertap unit.

    Doesn't matter if you get one for 405 / 705 or whatever.
    Jibbering Sports Stuff: http://jibbering.com/sports/
  • hopper1hopper1 Posts: 4,389
    Jim, is there anywhere I can get instructions for this process? :?
    Start with a budget, finish with a mortgage!
  • DaveyLDaveyL Posts: 5,167
    jibberjim wrote:
    hopper1 wrote:
    Plenty of dongles, cheers Jim. :wink:
    The dongles only seem to mention Forerunner 50, or 405's, is there a specific model for the 705, or are the all generic fit?

    They're for your PC, they won't talk to the 705, you use the PC and the dongle to talk to the powertap unit.

    Doesn't matter if you get one for 405 / 705 or whatever.

    Presumably this is how you get a live feed from your PowerTap into Golden Cheetah? (Not sure if it can actually do this yet but I'm sure I read about it!)
    Le Blaireau (1)
  • yep. its possible. when in spain (bonmati girona) I saw a rabobank car out with a laptop collecting a riders ANT data live from his TT bike.
  • hopper1hopper1 Posts: 4,389
    hopper1 wrote:
    Jim, is there anywhere I can get instructions for this process? :?

    Doh!
    Sorry Jim, I've only just noticed the link to your musings!
    Thank you for that.
    I'll have a go at it when I get home... see how it all pans out!
    Hopefully the 'dongle' will have arrived by then... It is attached to more equipment that I don't really need, but do really need, if you see what I mean! :roll: :oops: :wink:
    Start with a budget, finish with a mortgage!
  • PokerfacePokerface Posts: 7,960
    Well - checked my Garmin against my LYC - and they match. I guess I just wasn't pushing hard enough at the time!
  • jibberjimjibberjim Posts: 2,810
    hopper1 wrote:
    Sorry Jim, I've only just noticed the link to your musings!
    Thank you for that.
    I'll have a go at it when I get home... see how it all pans out!
    Hopefully the 'dongle' will have arrived by then... It is attached to more equipment that I don't really need, but do really need, if you see what I mean! :roll: :oops: :wink:

    Yep, feel free to drop me an email, or anything if you need any more help on it!
    Jibbering Sports Stuff: http://jibbering.com/sports/
  • chrisw12chrisw12 Posts: 1,246
    jibberjim wrote:
    hopper1 wrote:
    Sorry Jim, I've only just noticed the link to your musings!
    Thank you for that.
    I'll have a go at it when I get home... see how it all pans out!
    Hopefully the 'dongle' will have arrived by then... It is attached to more equipment that I don't really need, but do really need, if you see what I mean! :roll: :oops: :wink:

    Yep, feel free to drop me an email, or anything if you need any more help on it!

    Please don't do that, this is a very interesting and informative thread if you've got a powertap. I'll be interested how Hopper gets on.
  • jibberjimjibberjim Posts: 2,810
    edited June 2010
    chrisw12 wrote:
    JibberJim wrote:
    Yep, feel free to drop me an email, or anything if you need any more help on it!

    Please don't do that, this is a very interesting and informative thread if you've got a powertap. I'll be interested how Hopper gets on.

    Yeah, but the complicated parts of getting it hooked up are all working with virtual machines and playing with linux, not really the on topic relevance of testing the PT, which hopefully can stay here!
    Jibbering Sports Stuff: http://jibbering.com/sports/
  • hopper1hopper1 Posts: 4,389
    Thanks, Jim...
    When I get home (mid next week), I'll be in touch, to get this all resolved.

    chrisw12, once it's all done, I will post all info up on here for those interested. :wink:
    Start with a budget, finish with a mortgage!
  • amaferangaamaferanga Posts: 6,789
    Is the software easy enough to set up once you have the virtual machine and linux installed? I've set up VMs at work and it wasn't that much of a headache, but if the Quarqd stuff requires a degree in computer science to set up then I'll be stuffed.
    More problems but still living....
  • hopper1hopper1 Posts: 4,389
    amaferanga wrote:
    Is the software easy enough to set up once you have the virtual machine and linux installed? I've set up VMs at work and it wasn't that much of a headache, but if the Quarqd stuff requires a degree in computer science to set up then I'll be stuffed.

    You'll be stuffed!... I've spent 26 years mastering a sledge hammer and a 48 :shock:
    If I can't install it with the 48, then I mash it with the sledgey... :twisted: :twisted:
    Start with a budget, finish with a mortgage!
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