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Big jump in Quarq Calibration Numbers
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I put a whole new drivetrain on my bike with the exception of my Quarq Cinco and cranks. My calibration numbers used to be around 170 for years and now they have jumped to around 245 consistently for a few weeks. Is that normal?

I'm having trouble hitting my power numbers in training with a race coming up in a week so can't retest FTP to set new baseline. I looked back at some hill repeats before and after the swap thinking these would be least affected by different conditions at a slow speed. I may be answering my own question but there was around a 10 watt difference for about a 5:20 effort at 290-300 watts. The reported watts were consistently lower after the swap.
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Re: Big jump in Quarq Calibration Numbers [Stelvio] [ In reply to ]
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Re: Big jump in Quarq Calibration Numbers [Mike Alexander] [ In reply to ]
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Thanks Mike. This was on page 5 of search results!

I'll try a battery this morning but will need to check the chainring bolts tourque and use the Qalvin tool. I'll have to go back to the shop for that, wish this week wasn't so busy and I could get it done before my race.
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Re: Big jump in Quarq Calibration Numbers [Stelvio] [ In reply to ]
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Wasn't the battery and there was no moisture in the battery compartment. My torque wrench doesn't' go high enough to check that now.
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Re: Big jump in Quarq Calibration Numbers [Stelvio] [ In reply to ]
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Stelvio wrote:
I put a whole new drivetrain on my bike with the exception of my Quarq Cinco and cranks. My calibration numbers used to be around 170 for years and now they have jumped to around 245 consistently for a few weeks. Is that normal?

I'm having trouble hitting my power numbers in training with a race coming up in a week so can't retest FTP to set new baseline. I looked back at some hill repeats before and after the swap thinking these would be least affected by different conditions at a slow speed. I may be answering my own question but there was around a 10 watt difference for about a 5:20 effort at 290-300 watts. The reported watts were consistently lower after the swap.

The jump you described wouldn't result in 10w.

The zero offset # is measured in 32nds (don't ask) of a Nm. So (245-170)/32*(80rpm/60spm) -- essentially, the difference in zero offsets, divided by 32, to give the difference in Nm, multiplied by a cadence of 80rpm, divided by 60 to give revolutions per second. At 80rpm, that'd be a difference of 3w, or about 1%, which is well within the stated accuracy of 1.5%.

Now, with that said, the jump in zero offsets could be indicative of slope drift, and even a very minor drift in slope could be enough to throw your ride by 10w.

But strictly speaking in absolute terms, a zero offset jump of 70 "points" is not enough to be problematic in terms of affecting accuracy.

EDIT: my mistake. Forgot the 2*pi factor for conversion to radians per sec. So multiply that 3w by 6.28 or 18.8w...

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp
Last edited by: Rappstar: Jun 18, 17 14:19
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Re: Big jump in Quarq Calibration Numbers [Rappstar] [ In reply to ]
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Rappstar wrote:
Stelvio wrote:
I put a whole new drivetrain on my bike with the exception of my Quarq Cinco and cranks. My calibration numbers used to be around 170 for years and now they have jumped to around 245 consistently for a few weeks. Is that normal?

I'm having trouble hitting my power numbers in training with a race coming up in a week so can't retest FTP to set new baseline. I looked back at some hill repeats before and after the swap thinking these would be least affected by different conditions at a slow speed. I may be answering my own question but there was around a 10 watt difference for about a 5:20 effort at 290-300 watts. The reported watts were consistently lower after the swap.


The jump you described wouldn't result in 10w.

The zero offset # is measured in 32nds (don't ask) of a Nm. So (245-170)/32*(80rpm/60spm) -- essentially, the difference in zero offsets, divided by 32, to give the difference in Nm, multiplied by a cadence of 80rpm, divided by 60 to give revolutions per second. At 80rpm, that'd be a difference of 3w, or about 1%, which is well within the stated accuracy of 1.5%.

Now, with that said, the jump in zero offsets could be indicative of slope drift, and even a very minor drift in slope could be enough to throw your ride by 10w.

But strictly speaking in absolute terms, a zero offset jump of 70 "points" is not enough to be problematic in terms of affecting accuracy.

Jordan,

I think you're off on that estimate. IIRC each 1/32 Nm At 90rpm is ~ .33 watts so a difference of 75 would cause more on the order of a 25 watt shift rather than 3 watts. I'll get my thinking cap out and actually compute it.

Hugh

Genetics load the gun, lifestyle pulls the trigger.
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Re: Big jump in Quarq Calibration Numbers [Rappstar] [ In reply to ]
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Rappstar wrote:
Stelvio wrote:
I put a whole new drivetrain on my bike with the exception of my Quarq Cinco and cranks. My calibration numbers used to be around 170 for years and now they have jumped to around 245 consistently for a few weeks. Is that normal?

I'm having trouble hitting my power numbers in training with a race coming up in a week so can't retest FTP to set new baseline. I looked back at some hill repeats before and after the swap thinking these would be least affected by different conditions at a slow speed. I may be answering my own question but there was around a 10 watt difference for about a 5:20 effort at 290-300 watts. The reported watts were consistently lower after the swap.


The jump you described wouldn't result in 10w.

The zero offset # is measured in 32nds (don't ask) of a Nm. So (245-170)/32*(80rpm/60spm) -- essentially, the difference in zero offsets, divided by 32, to give the difference in Nm, multiplied by a cadence of 80rpm, divided by 60 to give revolutions per second. At 80rpm, that'd be a difference of 3w, or about 1%, which is well within the stated accuracy of 1.5%.

Now, with that said, the jump in zero offsets could be indicative of slope drift, and even a very minor drift in slope could be enough to throw your ride by 10w.

But strictly speaking in absolute terms, a zero offset jump of 70 "points" is not enough to be problematic in terms of affecting accuracy.

A 70 unit point drift on a Quarq most definitely is problematic.

Angular velocity is measured in radians per second, not revs per sec.
Hence an error of 70 x 1/32 Nm torque units on a Quarq at 80rpm will mean:

70 / 32 * 80rpm / 60sec/min * 2 * Pi = 18.3W

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Re: Big jump in Quarq Calibration Numbers [AlexS] [ In reply to ]
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Thank you to you and Hugh for correcting my math.

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp
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Re: Big jump in Quarq Calibration Numbers [Rappstar] [ In reply to ]
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Wow 18.3 watts is a lot. I don't have the time to get re-calibrated before my race. I can certainly race by adjusting to lower output number, just messes up the continuity of the values over time. Thanks for working out the math!!!
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Re: Big jump in Quarq Calibration Numbers [Stelvio] [ In reply to ]
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Stelvio,

Just because the zero offset has shifted it doesn't mean that the slope of the unit has changed. As long as the new ZO is consistent, it's quite likely the unit is actually fine. Your method of testing it via climb time on a hill isn't precise enough to really sift out a 10 watt difference. FWIW I've seen several Quarqs have ZO shifts when moved from one bike to another with no harm to their slope. Now when the ZO shifts a good bit within rides you're in a worse situation.

YMMV,

Hugh

Genetics load the gun, lifestyle pulls the trigger.
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Re: Big jump in Quarq Calibration Numbers [sciguy] [ In reply to ]
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sciguy wrote:
Stelvio,

Just because the zero offset has shifted it doesn't mean that the slope of the unit has changed. As long as the new ZO is consistent, it's quite likely the unit is actually fine. Your method of testing it via climb time on a hill isn't precise enough to really sift out a 10 watt difference. FWIW I've seen several Quarqs have ZO shifts when moved from one bike to another with no harm to their slope. Now when the ZO shifts a good bit within rides you're in a worse situation.

YMMV,

Hugh

I have two quarqs that I use regularly - one with a 56T and one with a 54T. Whenever I swap them, there is - initially - a change in the ZO. However, after 30min of riding, the values return to normal. But immediately after swapping them, the ZO is out of whack by a bit. To be clear, I'm not referring to the difference in ZOs between the two quarqs; what I'm saying is that I know the ZO (approximately) for each one, and when I install a given quarq, there's a delta of about 30-60 "points" at first which returns to normal after about 20-30min of riding.

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp
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Re: Big jump in Quarq Calibration Numbers [Rappstar] [ In reply to ]
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I was once told by someone way smarter than me, that knew the math, that the simple way of looking at it was to take the offset difference, and divide it by 3 to get the difference in the wattage readings. I know there can be a difference based on cadence, so it's just a ballpark estimate.

That said, I keep forgetting if it's more or less watts.

So if your reading increases from 100 to 160, or increases say from -160 to -100, that's a 60 point increase. Does that mean your PM was reading approximately 20 watts higher, or 20 watts lower prior to the recalibration?
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Re: Big jump in Quarq Calibration Numbers [sciguy] [ In reply to ]
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Thanks. Good to know. I do think things are off though. Beginning with the first ride after the change my power numbers have been lower but speeds have been up consistently. Obviously, in no way scientific except that it has happened consistently over the last 4 weeks on rides other than the climbs I mentioned earlier (those climbs were repeats, comparing 8 climbs vs. 32 over the prior few weeks). I'll get it recalibrated with a Qalvin and see if things change.
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