Frustrated with the numbers my Quarq is giving me - help me figure out what's going on

Aug 24, 12 7:16

Post #1 of 18 (8738 views)

I've trained with the same Powertap SL+ for the past 20 months and never had a problem with it or the numbers it gave me, I was actually quite happy with it. Lately I've moved to only racing cyclocross and so I thought having a crank based power meter would be the way to go so that I had power no matter which of my 3 tubular wheelsets I was using. I acquired a Quarq second hand from a teammate on Saturday. About 200 miles on the unit, SRAM 46/38 cyclocross rings were factory installed and calibrated. Since this is a different unit from my PT and it was that time anyway, I set out to do a new FTP test yesterday. I was waiting for my zero offset to "settle in" as it had gone from -295 to -650 to -715 to -720 to -740 from Sunday through yesterday; it now seems to be "stable" in the -695 to -740 range. I called Quarq twice about the offset moving quite a bit and both people I talked to assured me the offset would level out and it's nothing to worry about. I'm a numbers geek and obsess over my number so it's been a real challenge not to freak.

So I go out to do my test yesterday and I'm feeling something might be a bit off. Same protocol I've always used for dedicated FTP test, same location, variables are different bikes but set up quite similar. I wasn't expecting any big jumps in numbers yesterday because my training hasn't been super consistent due to life in general getting in the way, but I finished my local short track MTB series a few weeks ago and my racing tells me that my fitness hasn't dropped off a cliff or anything like that either.

Previous test
5' @404w avgHR 181 maxHR 186
20' @335w avgHR 177 max HR 184

yesterday
5' @396w avgHR 180 maxHR 188
12:29@304w avgHR180 maxHR 186
13:06@307w avgHR 183 maxHR 188

I shut the first 20min test down because I was dying, HR was way too high and power was way too low. Reset and tried again, same story. I consistently do 2x20 @300w with HR in the mid 150s. I manually zero'd before each test yesterday and the number was between -695 and -740 . I could have been having a bad day, but my 5' power wasn't that far off from what I was expecting. I have 2 other files from our weekly TT series 21:13 @ 337w no HR data and 21:11 @ 333w avgHR 176 maxHR 185.

Any ideas?

Last edited by: helios: Aug 24, 12 7:16

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [helios] [ In reply to ]

Aug 24, 12 7:30

Post #2 of 18 (8720 views)

did you check the offset after each test?

at constant cadence (say 90rpm), every 3 units is a watt, and drifting from -100 to -103 means you were actually doing 1W more work than what the Quarq was calculating as it applied a correction equivalent to what's needed for -100

that said, you could be off form and your 5 min may not suffer all that much. I certainly experienced increase in 5min power without doing much while watching FTP drop

in case you didn't know, quarq is quite moisture sensitive

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [echappist] [ In reply to ]

Aug 24, 12 7:53

Post #3 of 18 (8694 views)

Yesterday offset was -740 at the beginning of first test and -695 by the end of all testing. I'm familar with the 3pts = 1w which is why I was so concerned with the zero offset not being very consistent. That swing could theoretically account for ~15w, but not the other 15w. I zero'd before each test, but I don't remember exactly what it was each time, just the extremes stick in my mind. I'm just having a hard time imagining I've lost ~30w of threshold power when as recently as last week I was putting out 300w "comfrotably hard" for 20mins with a HR of 160bpm or less.

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [helios] [ In reply to ]

Aug 24, 12 8:29

Post #4 of 18 (8642 views)

Check the torque of the chain ring bolts. Use a good torque wrench and make sure they are even. If a bolt is loose, it will throw the offset off. If you do adjust the torque of the bolts, you'll have to go through the "settling in" process again.

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [echappist] [ In reply to ]

Aug 24, 12 8:36

Post #5 of 18 (8627 views)

echappist wrote:

did you check the offset after each test?

at constant cadence (say 90rpm), every 3 units is a watt, and drifting from -100 to -103 means you were actually doing 1W more work than what the Quarq was calculating as it applied a correction equivalent to what's needed for -100

that said, you could be off form and your 5 min may not suffer all that much. I certainly experienced increase in 5min power without doing much while watching FTP drop

in case you didn't know, quarq is quite moisture sensitive

Actually, the Quarq is virtually immune to moisture. EVERY Quarq unit undergoes a simple - but important - test before leaving the factory. It sits in a bucket of water for 20min and then undergoes a recheck of all functions. If there is one thing a Quarq is NOT, it's "moisture sensitive." And, due to Jim's excellent work in FEA, it's also quite resistant to temperature swings, because the strain gauges are placed on the spider in such a way that as the spider expands/contracts with temperature, the net effect on the strain gauges is minimized.

When you see a big change in zero offset, that MIGHT be that your chainring bolts are coming loose. If you have a torque wrench, you can re-check the torque on the bolts. That being said, the settling of the offset value is often just the bolts themselves stretching (which is normal) and settling in.

To the OP, best thing to do is ride with both the PT and the quarq together for a bit to see if they correlate. It's normal for powermeters to read differently, though in my experience, the quarq and powertap values read very similar (within margin of error).

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [helios] [ In reply to ]

Aug 24, 12 8:41

Post #6 of 18 (8616 views)

Although I love my quarq, I have had similar problems as has a friend. I've always felt my PT numbers are more consistent.

I think that if you give it another week the numbers will settle down and be internally consistent. One thing I have learned this summer having had essentially 4 PM's (old Quarq, replacement Quarq, re-replacement Quarq, PT while Quarq was in the shop) is that they all seem to vary in their readings--by a significant margin. I've essentially had 4 ftps this year, makes it confusing!! (I did like it when they first sent the replacement unit and it was reading way high--felt studly, briefly). A year ago, I just kind of assumed that PM's were roughly similar withing a 2-3% range. I don;t believe that at all anymore. In fact, just to make sure I wasn;t crazy, I hooked up the replacement Quarq and the PT at the same time and ran different head units and the numbers were significantly different, but internally consistent, i.e., when the PT went up so did the Quarq and by roughly the same percentage. I think all you can hope for is internal consistency within your unit. I think you'll get that within another week and at that point you just need to reset your ftp in line with whatever the unit is reading.

Edit: see Rappstar post above. My variance was NOT within the margin of error even assuming both units had a directly opposite margin of error of 2%.

Last edited by: phil combs: Aug 24, 12 8:45

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [Rappstar] [ In reply to ]

Aug 24, 12 8:50

Post #7 of 18 (8601 views)

I've also recently moved from PT to quarq. I use an Edge 500 - am I meant to calibrate it every ride? and what is the correct method - pedaling backwards during calibration or not pedaling at all?

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [amagangan] [ In reply to ]

Aug 24, 12 8:55

Post #8 of 18 (8585 views)

Yes - when I say I zero'd before every test I mean I used the Calibrate function on the Edge 500 (or my iPhone's Qalvin app) to "manually zero" the unit. Pedal backwards to make sure the Quarq is awake and then place the driveside crankarm at 6 o'clock. Pedaling backwards 4 times during a ride should also Auto Zero the Quarq.

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [Rappstar] [ In reply to ]

Aug 24, 12 9:46

Post #9 of 18 (8546 views)

Rappstar wrote:

echappist wrote:

did you check the offset after each test?

at constant cadence (say 90rpm), every 3 units is a watt, and drifting from -100 to -103 means you were actually doing 1W more work than what the Quarq was calculating as it applied a correction equivalent to what's needed for -100

that said, you could be off form and your 5 min may not suffer all that much. I certainly experienced increase in 5min power without doing much while watching FTP drop

in case you didn't know, quarq is quite moisture sensitive

Actually, the Quarq is virtually immune to moisture. EVERY Quarq unit undergoes a simple - but important - test before leaving the factory. It sits in a bucket of water for 20min and then undergoes a recheck of all functions. If there is one thing a Quarq is NOT, it's "moisture sensitive." And, due to Jim's excellent work in FEA, it's also quite resistant to temperature swings, because the strain gauges are placed on the spider in such a way that as the spider expands/contracts with temperature, the net effect on the strain gauges is minimized.

When you see a big change in zero offset, that MIGHT be that your chainring bolts are coming loose. If you have a torque wrench, you can re-check the torque on the bolts. That being said, the settling of the offset value is often just the bolts themselves stretching (which is normal) and settling in.

To the OP, best thing to do is ride with both the PT and the quarq together for a bit to see if they correlate. It's normal for powermeters to read differently, though in my experience, the quarq and powertap values read very similar (within margin of error).

what you said means that the Quarq has the ability to withstand moisture and not short circuit, but does nothing to address the fact that the pressure on the spider will change due to moisture. The electronics can all be hermetically sealed, but if the forces on the spider itself changes, the reading will still be off.

i know they endorse you, but what you are saying is false. I called up Quarq three time regarding this, and that's what the reps told me. Furthermore, I was told that this has not been addressed with the latest iteration of Quarqs.

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [echappist] [ In reply to ]

Aug 29, 12 11:12

Post #10 of 18 (8374 views)

echappist wrote:

Rappstar wrote:

echappist wrote:

did you check the offset after each test?

at constant cadence (say 90rpm), every 3 units is a watt, and drifting from -100 to -103 means you were actually doing 1W more work than what the Quarq was calculating as it applied a correction equivalent to what's needed for -100

that said, you could be off form and your 5 min may not suffer all that much. I certainly experienced increase in 5min power without doing much while watching FTP drop

in case you didn't know, quarq is quite moisture sensitive

Actually, the Quarq is virtually immune to moisture. EVERY Quarq unit undergoes a simple - but important - test before leaving the factory. It sits in a bucket of water for 20min and then undergoes a recheck of all functions. If there is one thing a Quarq is NOT, it's "moisture sensitive." And, due to Jim's excellent work in FEA, it's also quite resistant to temperature swings, because the strain gauges are placed on the spider in such a way that as the spider expands/contracts with temperature, the net effect on the strain gauges is minimized.

When you see a big change in zero offset, that MIGHT be that your chainring bolts are coming loose. If you have a torque wrench, you can re-check the torque on the bolts. That being said, the settling of the offset value is often just the bolts themselves stretching (which is normal) and settling in.

To the OP, best thing to do is ride with both the PT and the quarq together for a bit to see if they correlate. It's normal for powermeters to read differently, though in my experience, the quarq and powertap values read very similar (within margin of error).

what you said means that the Quarq has the ability to withstand moisture and not short circuit, but does nothing to address the fact that the pressure on the spider will change due to moisture. The electronics can all be hermetically sealed, but if the forces on the spider itself changes, the reading will still be off.

i know they endorse you, but what you are saying is false. I called up Quarq three time regarding this, and that's what the reps told me. Furthermore, I was told that this has not been addressed with the latest iteration of Quarqs.

I'm sorry, but you must have misunderstood. I forwarded this thread to Jim Meyer, Quarq's founder and head engineer, and discussed it with him because I couldn't conceive of any way that what you were saying made sense. And neither did Jim.

His reply, "Humidity and air density are not related to the power measurement in any way."

Sorry for any misunderstanding you may have had with tech support. Air density (and humidity, because it affects air density) does certainly affect the power required to go a given speed. Maybe that's what you misunderstood? Not sure. But the Quarq itself is not in any way "moisture sensitive."

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [Rappstar] [ In reply to ]

Aug 29, 12 11:57

Post #11 of 18 (8331 views)

Rappstar wrote:

I'm sorry, but you must have misunderstood. I forwarded this thread to Jim Meyer, Quarq's founder and head engineer, and discussed it with him because I couldn't conceive of any way that what you were saying made sense. And neither did Jim.

His reply, "Humidity and air density are not related to the power measurement in any way."

First let me say that I currently own two Quarq's (having owned 2 each of SRMs and PTs and also a Polar unit in the past) and I think that they are excellent -- the most reliable PM in terms of failure rate in my experience and very consistent and accurate as long as you install the chainrings properly. I would recommend them to anyone in a second.

That said, in my experience if you soak the crank in water, e.g. if you pressure wash your bike, the zero offset can sometimes temporarily drop by up to 100 pts -- by "temporarily" I mean that the ZO will slowly revert over about the next day. My (rather uneducated) guess is that the water gets in between the chainrings and lubricates things a bit so that there is more slip/stretch in the system. This is no big deal as long as you zero your PM.

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [lanierb] [ In reply to ]

Aug 29, 12 14:33

Post #12 of 18 (8259 views)

lanierb wrote:

Rappstar wrote:

I'm sorry, but you must have misunderstood. I forwarded this thread to Jim Meyer, Quarq's founder and head engineer, and discussed it with him because I couldn't conceive of any way that what you were saying made sense. And neither did Jim.

His reply, "Humidity and air density are not related to the power measurement in any way."

First let me say that I currently own two Quarq's (having owned 2 each of SRMs and PTs and also a Polar unit in the past) and I think that they are excellent -- the most reliable PM in terms of failure rate in my experience and very consistent and accurate as long as you install the chainrings properly. I would recommend them to anyone in a second.

That said, in my experience if you soak the crank in water, e.g. if you pressure wash your bike, the zero offset can sometimes temporarily drop by up to 100 pts -- by "temporarily" I mean that the ZO will slowly revert over about the next day. My (rather uneducated) guess is that the water gets in between the chainrings and lubricates things a bit so that there is more slip/stretch in the system. This is no big deal as long as you zero your PM.

you put it a lot better than I did. The only issue the the no big deal as long as you zero the PM b/c it'll change during the ride, so lots of back pedaling needed on a rainy day. I have personally seen swings of 30-40 units within 30 minutes, That said, they do eventually return to normal 1-2 days after a rainy ride.

but regardless, I still love my rotor quarq and would enthusiastically recommend quarqs to anyone who asks.

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [Rappstar] [ In reply to ]

Jun 23, 15 7:18

Post #13 of 18 (6229 views)

Rappstar wrote:

echappist wrote:

Rappstar wrote:

echappist wrote:

did you check the offset after each test?

at constant cadence (say 90rpm), every 3 units is a watt, and drifting from -100 to -103 means you were actually doing 1W more work than what the Quarq was calculating as it applied a correction equivalent to what's needed for -100

that said, you could be off form and your 5 min may not suffer all that much. I certainly experienced increase in 5min power without doing much while watching FTP drop

in case you didn't know, quarq is quite moisture sensitive

Actually, the Quarq is virtually immune to moisture. EVERY Quarq unit undergoes a simple - but important - test before leaving the factory. It sits in a bucket of water for 20min and then undergoes a recheck of all functions. If there is one thing a Quarq is NOT, it's "moisture sensitive." And, due to Jim's excellent work in FEA, it's also quite resistant to temperature swings, because the strain gauges are placed on the spider in such a way that as the spider expands/contracts with temperature, the net effect on the strain gauges is minimized.

When you see a big change in zero offset, that MIGHT be that your chainring bolts are coming loose. If you have a torque wrench, you can re-check the torque on the bolts. That being said, the settling of the offset value is often just the bolts themselves stretching (which is normal) and settling in.

To the OP, best thing to do is ride with both the PT and the quarq together for a bit to see if they correlate. It's normal for powermeters to read differently, though in my experience, the quarq and powertap values read very similar (within margin of error).

what you said means that the Quarq has the ability to withstand moisture and not short circuit, but does nothing to address the fact that the pressure on the spider will change due to moisture. The electronics can all be hermetically sealed, but if the forces on the spider itself changes, the reading will still be off.

i know they endorse you, but what you are saying is false. I called up Quarq three time regarding this, and that's what the reps told me. Furthermore, I was told that this has not been addressed with the latest iteration of Quarqs.

I'm sorry, but you must have misunderstood. I forwarded this thread to Jim Meyer, Quarq's founder and head engineer, and discussed it with him because I couldn't conceive of any way that what you were saying made sense. And neither did Jim.

His reply, "Humidity and air density are not related to the power measurement in any way."

Sorry for any misunderstanding you may have had with tech support. Air density (and humidity, because it affects air density) does certainly affect the power required to go a given speed. Maybe that's what you misunderstood? Not sure. But the Quarq itself is not in any way "moisture sensitive."

Any idea then why after my second wet and rainy ride in my quarq, my zero offsets go to some crazy number like 1800 or so?? Like I said, this is the second time this has happened. I'd say I spent 20 minutes riding in pouring rain and when I get home, I dry everything off but the next morning, my offset number is significantly higher than normal. Usually I'm about 350 or so, but after a wet ride I'm up to 1800 or 1700 and I can tell that my power numbers are coming in much lower than normal. After the first time, the offset and numbers eventually returned to normal, but right now, after my second wet ride last night, my calibration is high and my power numbers are low. Any thoughts?

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [echappist] [ In reply to ]

Jun 23, 15 7:29

Post #14 of 18 (6208 views)

Perhaps try to remove the impact of backpedalling resistance on the zero offset process. Try turning auto-zero off and manually zeroing the Quarq. That will remove the drivetrain dependence on zeroing.

AndyF
bike geek

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [echappist] [ In reply to ]

Jun 23, 15 7:33

Post #15 of 18 (6199 views)

echappist wrote:

Rappstar wrote:

echappist wrote:

did you check the offset after each test?

at constant cadence (say 90rpm), every 3 units is a watt, and drifting from -100 to -103 means you were actually doing 1W more work than what the Quarq was calculating as it applied a correction equivalent to what's needed for -100

that said, you could be off form and your 5 min may not suffer all that much. I certainly experienced increase in 5min power without doing much while watching FTP drop

In case you didn't know, quarq is quite moisture sensitive

Actually, the Quarq is virtually immune to moisture. EVERY Quarq unit undergoes a simple - but important - test before leaving the factory. It sits in a bucket of water for 20min and then undergoes a recheck of all functions. If there is one thing a Quarq is NOT, it's "moisture sensitive." And, due to Jim's excellent work in FEA, it's also quite resistant to temperature swings, because the strain gauges are placed on the spider in such a way that as the spider expands/contracts with temperature, the net effect on the strain gauges is minimized.

When you see a big change in zero offset, that MIGHT be that your chainring bolts are coming loose. If you have a torque wrench, you can re-check the torque on the bolts. That being said, the settling of the offset value is often just the bolts themselves stretching (which is normal) and settling in.

To the OP, best thing to do is ride with both the PT and the quarq together for a bit to see if they correlate. It's normal for powermeters to read differently, though in my experience, the quarq and powertap values read very similar (within margin of error).

what you said means that the Quarq has the ability to withstand moisture and not short circuit, but does nothing to address the fact that the pressure on the spider will change due to moisture. The electronics can all be hermetically sealed, but if the forces on the spider itself changes, the reading will still be off.

i know they endorse you, but what you are saying is false. I called up Quarq three time regarding this, and that's what the reps told me. Furthermore, I was told that this has not been addressed with the latest iteration of Quarqs.

Yup...and the experience of the OP is precisely why a certain young data-driven, biomedical-engineer-turned-med-student I know eventually ditched his Quarqs for SRMs.

ETA: More info here: https://groups.google.com/...attage/quarq$20drift

Last edited by: Andrew Coggan: Jun 23, 15 8:36

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [drluke12] [ In reply to ]

Jun 26, 15 8:46

Post #16 of 18 (6019 views)

Perhaps check to make sure your battery compartment is tight? There's a small torx screw inside. Perhaps it's loose and water is getting in on the backside?

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [Rappstar] [ In reply to ]

Jun 26, 15 8:51

Post #17 of 18 (6014 views)

Well, as expected, and as mentioned previously in this thread, everything comes back to normal after a day or two when everything dries out. This is the second time this has happened to me after riding in the rain. I can report now that my calibration numbers are completely normal and consistent to what they were prior to getting caught in the rain. I would think that if water was getting into the unit, it would permanently destroy the electronics? As a side note, I also had some electrical tape wrapped around the battery cover case to hopefully avoid water getting in (which is what I was thinking happened the first time). I really don't think any water got into the battery area, because I did inspect it after the ride. Could it be (as someone else mentioned) that water gets into the area between the chainrings/spider and messes with the calibration?? I think if this happens again, I will just avoid re calibrating the PM for a few days.

Thanks for the feedback.

Re: Frustrated with the numbers my Quarq is giving me - help me figure out what's going on [Andrew Coggan] [ In reply to ]

Jun 26, 15 8:52

Post #18 of 18 (6009 views)

The older model quarqs had issues, the newer versions are much superior in terms of issues. I am sure there are still examples of failures, (as there are with any device including the so called "gold standard"), but the design for both water resistance and zero offset drift has improved dramatically.

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