The zero offset changes with temperature, but any long-term changes (barring global warming <g>) are due to changes in the state of the battery in the crank. As it runs runs down (over years - our track SRM from 2002 is still going strong on its original battery) the zero offset will gradually decrease.

What Tom A. and I were discussing were changes in the slope itself. At least at one point, this would drift steadily for a couple of years, then begin to stabilize (and as I mentioned, neither of ours have seemingly changed in 5+ y). SRM blamed this on a bad batch of epoxy that required a long time to cure, but I've always wondered if perhaps it weren't due to "work hardening" of the crank spider to which the strain gages are bonded (any engineers out there, feel free to chime in and correct me if this isn't possible/logical).

I am no expert in any way. I am a new power user, owner of Cinqo/Edge 500.
I don't think either system is better than the other. For me, it was a pure price. I wanted wireless/ ANT+ system, no wires......No way I was going to pay for SRM in my wildest dreams, even if I had the money. I don't care how long it has been on the market.
Cinqo turned for me as a lot more viable option given the fact that I am a father of two, triathlon is my hobby.
On the other hand (I was born and raised in Europe), I found that many European products are over priced.
I used to be an Audi owner. This power meter comparison has a lot in common with this comparison(if you know about cars):
line up
Audi RS4 $76000
BMW M3 $65000+
Mitsubishi Lancer Evolution X $35000
Subaru WRX STI $40000

In many cases, on track, both Japanese vehicles can run in circles around German heavy weights.
Hope you get the message with this story.

Can I show this to my wife? We are picking up her new BMW 5 series friday. She is killing me. It was her justification to me getting at 2010 ttx 9.9 with bells and whistles and all the training hours I'm doing for IMLP. Payback was a bitch!

Hey, at least you got a bike out of the deal. I've gotta pay her in full before I even get the blasted bike. 10 months left to go.

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"The solution is to just go faster"

Like I said above...all you need to do is buy a cheap ANT+ dongle for your computer and download quarq-d and you're good to go ;-)

http://webapps.nuhorizons.com/...efront/PartSearch.do

http://opensource.quarq.us/quarqd/

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http://bikeblather.blogspot.com/

Except...one typically needs to both change a battery AND calibrate the slope on an SRM...while with a Quarq it's typically just change a battery ;-)

And...if one REALLY needs to calibrate the CinQo...see my post above to AC about how you can go about doing it. And, unlike changing the battery yourself on an SRM, changing the slope cal on a CinQo doesn't void the warranty :-)

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http://bikeblather.blogspot.com/

I can understand that rationale, especially from a user such as yourself whom I would consider qualified enough to interpret and adjust the slope. I would not be surprised to find that many 'average' users don't even remember to zero their torque offsets before most rides, i.e. they don't even always use the basic features that they do have available let alone much more advanced and infrequently used features such as slope adjustment.

As I've stated in the past, I don't believe either the SRM or the Quarq is the ‘best’ power meter, nor that such a thing that exists, what is best is dependent on your unique needs. Admittedly subjectively, when it comes to crank-based I feel that the Quarq + Edge 500/705/310xt/Joule/etc options are both more affordable and flexible for many if not most users, but I still see the cases where and understand why some will always prefer SRM.

Go with the quark. It works just fine and it will save you money.

And so am having been pounded by hail during a race in a heavy thunderstorm resulting in the display on my SRM PC VI going blank late in the race despite having been fully charged before the start this past Saturday. Worse yet, after charging the PC VI overnight, while the display came back, there was no data from the previous days racing in the devices memory. Ironically there were several Garmin Edge 500 users in the in the lead group alongside me, none of whom had issues with the computer going flat and while I had been on the fence between getting the new PC VII or an Edge 500, this past weekend helped me decide and I am now waiting on a Garmin Edge 500 to arrive in the mail.

Back on topic, despite my issue with the SRM PC VI, if the discussion is limited to the power meter itself and not the head units, then as an owner of 1 wired and 2 wireless SRM's, I also think that it is the gold standard. As for fidgeting to make it work, other than 30-40 seconds to pair the PC VI head unit to the power meter and the ANT+ speed sensor on the road and time trial bikes and another 15-20 seconds for zero offeset, the issue this past weekend has been my only problem with SRM's. But like you, I just can't justify paying nearly $1000 for a new Power Control that offers very little in terms of customization to suit the needs of my training and racing.

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¯\_(ツ)_/¯

 

Like I said above...all you need to do is buy a cheap ANT+ dongle for your computer and download quarq-d and you're good to go ;-)

http://webapps.nuhorizons.com/...efront/PartSearch.do T

http://opensource.quarq.us/quarqd/[/reply]
Tom have you actually done a hanging mass calibration on your Quarq to see how the slope compares to the one provided
by the manufactures? By the way,the link to Nuhorizons doesn't lead me to a dongle.

Thanks for the useful information!

SciGuy

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Genetics load the gun, lifestyle pulls the trigger.

[/reply]
Or you can push a few buttons on your SRM PowerControl and change the slope w/o any need for a laptop or desktop computer...very convenient when you find yourself a quarter-mile from home wondering why your displayed power doesn't match your expectations, only to remember that you last used the PowerControl with a different crank. :-)

You don't need the dongle or quarqd to check the slope calibration on a Quarq...with a 705, when you manually zero through the head unit, you're returned a number that's the torque offset in N-m x 32. So, you just compare the torque offset returned with no weight hung from the pedal with the offset returned when the weight is hung. Make sense? And yes...I've done that...and it's always been within specs for me.

Search for "antusb1" on the nuhorizons site. Sorry about that.

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http://bikeblather.blogspot.com/

I am not Tom, nor have I performed a static calibration of the Quarq lent to me (due to the limitations of current ANT+ head units as mentioned previously). What I have done, however, is performed some dynamic comparisons:



Note that data were collected using the same chain, derailleur, and cassette, that the SRM and PowerTap in question were statically calibrated using the same set of weights, and that Quarq verified the calibration of their crank between (IIRC) the 2nd and 3rd trials.

Great post.

The iAero still doesn't return the torque offset value when manually zeroing through the head? Huh...

You don't know someone with a 705 you could borrow for a torque check session?

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http://bikeblather.blogspot.com/

No, and maybe.

Here's the thing, though: suppose I was able to borrow a Garmin and did a static calibration of the Quarq using the same set of weights that I used to calibrate my SRM and PowerTap: either the results would agree with the dynamic comparison, in which case I haven't learned much, or they wouldn't, in which case I'd be more inclined to trust the dynamic comparison, at least in a relative sense. My motivation for performing such a test therefore isn't particularly high.

Is there something special about this dongle? I'm assuming anyone who has a Quarq already has an ANT+ dongle, you need an ANT+ head unit and every head unit should come with a dongle, i.e. the Garmin USB ANT Stick. Or would those not work?

Personally I'm not going to mess with Quarq-d anyway, just was curious.

Not really...I didn't know that the Garmins come with a dongle...at least the 705 doesn't.

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http://bikeblather.blogspot.com/

The 310XT comes with an ANT+ dongle.

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

The 705 doesn't come with a dongle because it talks via USB mini to the computer and not via ANT+

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ishi no ue ni san nen | Perseverance will win in the end. | Blog | @nebmot | Strava | Instagram |

Aaah...because it doesn't have a USB input like the 705...got it.

The readme.txt of quarqd implies that the Garmin dongle is usable.

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http://bikeblather.blogspot.com/

You sure can. You may get us both in trouble, we will get banned from reading this forum. Just joking. Life is a compromise. It is ok as long as you get to drive the Bimmer from time to time.

Ah that was my mistake. Both my 405 and 310XT came with ANT+ USB dongles and I assumed that the Edge's did as well. Looking at the Garmin site, it looks like the Edge 500 doesn't even come with a wireless dongle? That seems bizarre to me.

Here is the official Quarq stance on field adjusting the slope.

We have a word to describe CinQos when the slope drifts: BROKEN. A well designed and well manufactured load cell will not drift in slope over time. The slope on the CinQo is very stable and does not require recalibration.

Moreover, measuring the slope to within 1% in the field is a somewhat technical process and requires a known weight. I expect that allowing general users to change the slope in the field will result in MORE slope error over the installed population of CinQo's than if we keep it buttoned down.

Now currently, changing the chainrings from road to TT does change the effective slope. (Road rings are about the same, and TT rings are about the same, but switching is about 5% different.) This is a legitimate reason to need to adjust the slope. We are working to address this to this and expect to have
a solution by the end of the year. This solution will be compatible with all existing CinQos.

So the Quarq CinQo is better than the SRM because the battery is user replaceable, the slope does not drift over time and it costs less.

On another day I will take issue with the 'gold standard' myth. But not today, as we are still digging out of our backlog of orders. ;-)

Jim

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James Meyer
Quarq Founder / SRAM

You could just operate like the credit card world and call yourself the "platinum" standard. Platinum, diamond, titanium, carbon, black, etc. are all the new "gold." Gold is so last millennium.

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