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PostPosted: Sun Jun 10, 2012 2:12 am 
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Joined: Sun Apr 24, 2011 2:21 am
Posts: 258
I bought myself a new powertap G3 wheelset pretty recently, but there is one problem. The calibration value is WAY OFF.


From what I understand, the value should be 512 +-12. Mine is -3471. As a result, all my power and cadence values are zero.


I use a Garmin 500 & 800. Does anyone know how to recalibrate the powertap so it can read accurately?


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PostPosted: Sun Jun 10, 2012 3:57 am 
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Joined: Tue Sep 14, 2010 3:28 pm
Posts: 1390
Sounds like something is wrong with your hub. Do you have the latest firmware(3.0)?


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Posted: Sun Jun 10, 2012 3:57 am 


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PostPosted: Sun Jun 10, 2012 2:05 pm 
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Joined: Fri Jan 06, 2012 2:19 pm
Posts: 64
Have you tried to recalibrate it? I always do my calibration when off the bike. I THINK old PT designs wanted you to coast. Just making sure you're going through the right process.

If you've done all that, then likely you need to send the internals to saris.


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PostPosted: Mon Jun 11, 2012 5:24 pm 
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Joined: Mon Jun 11, 2012 5:21 pm
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When you calibrate using a Garmin head unit, the number you get back is the ANT+ ID of the Powertap. It is NOT the 512 number - you can only see that calibration number if you use the Joule head unit, unfortunately.


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PostPosted: Mon Jun 11, 2012 7:42 pm 
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Joined: Tue Dec 27, 2011 2:19 pm
Posts: 447
sounds about like my power levels, I think your good to go!

:thumbup: :thumbup: :thumbup:


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PostPosted: Wed Jul 03, 2013 3:44 am 
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Joined: Wed Jul 03, 2013 3:43 am
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Hi Ghost234, how did you go resolving the calibration?
Cheers
Stu


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PostPosted: Wed Jul 03, 2013 1:40 pm 
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Joined: Fri Sep 17, 2010 4:48 pm
Posts: 137
When you calibrate on a Garmin (500) you get two values:

One is the "Current Calibration" which should be between -512 and +512. Any value between is A-OK
The second is "Torque" which should be as close to zero as possible (provided you calibrate while not moving an after the hub has acclimatized to the temperature/pressure etc...

Having been through this MANY times (I'm on my 6th PT wheel on my winter bike- winter kills PTs. I also run a Quarq on my race bike) I hate to be the one to tell you but you're going to HAVE to send that wheel back to Saris as the strain gauges/torque tube are shot and will need to be replaced. If the wheel is under warranty it will be free (Saris may even send you a shipping label to get the wheel to them!) If it's not under warranty, well... Saris is really good about working with customers to find solutions. This doesn't mean it'll be free but they may have some options for you.

-J


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PostPosted: Wed Jul 03, 2013 2:02 pm 
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Shop Owner

Joined: Sun Jan 03, 2010 4:58 am
Posts: 360
I really like the Powertap system, but realiablity is not the best. Mine was in the shop 5 times in less than 1000 miles. Cost me a boat load of money for shipping and wheel building. After the fifth time, they gave me a new hub. That lasted a year before it was back in the shop.

Bought it while waiting for the Garmin, still waiting.


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PostPosted: Wed Jul 03, 2013 4:02 pm 
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Joined: Tue Jan 13, 2009 2:35 am
Posts: 417
dhague wrote:
When you calibrate using a Garmin head unit, the number you get back is the ANT+ ID of the Powertap. It is NOT the 512 number - you can only see that calibration number if you use the Joule head unit, unfortunately.


This was my experience as well.


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PostPosted: Wed Jul 03, 2013 5:42 pm 
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in the industry

Joined: Mon Sep 26, 2011 10:34 pm
Posts: 103
Location: Madison, WI
Garmins are a strange bunch when it comes to checking the calibration of a PowerTap. Previous generations of their firmware simply read the sensor ID rather than the calibration (as reported above), but they were supposed to have fixed that with an update. Personally, I haven't seen any consistency regarding it--some Garmins will read the proper three digit value, some will read a negative four or five digit value. I don't know the current status of what they are actually supposed to read, but I think I'll check in our management team on that. That said, they CAN do it.

The function called "calibrate" on a Garmin is what's actually a manual zero, also known as zeroing the torque. You want to do this when the hub has no force applied. Personally I don't recommend doing this while coasting. Just do it when the bike is not moving. If after doing this your power is still zero (or very high), the hub will have to come in for re-calibration. Be sure to check the power while actually riding and not just by spinning the wheel in a repair stand.

FYI you will still get cadence and speed from the hub even if it's out of calibration. Those metrics are not dependent upon the torque offset.

If you have further issues, drop me a PM and I'll help get you sorted.

_________________
Michael Fioretti
PowerTap Technical Support


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Posted: Wed Jul 03, 2013 5:42 pm 


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