Help! Powertap calibration is WAY off!

Discuss light weight issues concerning road bikes & parts.
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by Ghost234

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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by bricky21

Sounds like something is wrong with your hub. Do you have the latest firmware(3.0)?

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by mtnbkr

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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Joined: Mon Jun 11, 2012 5:21 pm

by dhague

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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by mjduct

sounds about like my power levels, I think your good to go!

:thumbup: :thumbup: :thumbup:

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by stut

Hi Ghost234, how did you go resolving the calibration?

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by showdown

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.


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by Butcher

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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by topflightpro

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.

in the industry
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Location: Madison, WI

by fio

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.

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Joined: Mon May 19, 2014 5:19 pm

by jmomentum

Can someone advise me on my Powertap G3. It is relatively new with only 1000 kms on it. It worked well until yesterday. During a normal ride which started out with normal power readings, the power readings on my Garmin Edge 500 became very high (3000-4000W). This seemed to happen suddenly and at random. I checked the calibration reading when I returned home and it was 239 instead of the normal 510. I did the firmware update, changed battery, and reset for 10 seconds. Still the calibration reading at zero torque is 239. Does anyone have experience with this product? Why would the calibration suddenly change? It seems odd to me and very frustrating. I really don't want to send my wheel in for service. That seems ridiculous for a brand new product.

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Joined: Wed Nov 02, 2011 2:17 pm

by RServranckx

Saris/PowerTap have excellent customer service, and will offer email or phone support at no charge - ask for their advice. They were really helpful when I had problems updating the firmware on my G3

I cannot help you with your specific problem. I did have one incident similar to yours, but it was resolved by replacing the G3's battery.


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by Causidicus

Last edited by Causidicus on Wed Jun 18, 2014 1:19 am, edited 1 time in total.

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by Butcher

Wishing you do not have to send it to the shop, is wasting your wishes. It needs to be sent away. Although Powertap has a nice service dept. it does not help much with the shipping. I have sent mine in and I only got free shipping once. You ship it to them and they send it back for free. Either way, it is a pain in the but.

Great service dept, but I do not ever see myself buying another Powertap product.

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Joined: Mon May 19, 2014 5:19 pm

by jmomentum

I assume this will have to be shipped to a US location? I am in Canada and I just confirmed that shipping my wheel will be $80. I can't see myself disassembling the wheel just to ship the hub. Is there any way to get a refund for this product? Maybe I'm just used to electronics but normally it's possible to get a full refund if a product is defective. I don't see why I should spend this money to have a new hub serviced. If I was guaranteed to not have this problem again then I might consider it to be worthwhile to repair but the last thing I want is to be sending in my wheel every six months.

I am incredibly disappointed in the fact that I spent about 2-3 years researching various power options before being comfortable with the new G3 price/option. I really thought reliability would be a strong point.

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