Stages Power Meter

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Re: Stages Power Meter

Postby Arlberg » Thu Mar 27, 2014 9:06 pm

toolonglegs wrote:Arlberg... 360w at 80kgs.


The 360 watts I can only hold for about 12-15 minutes on a climb. My actual FTP over an hour is more like 330.

Tested here, (I think you will need to log in to Strava to see them)

http://www.strava.com/activities/90952221/overview and here:
http://www.strava.com/activities/89930616/overview

both when I was 80kg.

I have since dropped another 2 kg and am now 78 kg by the way, and I am aiming for 76kg. From there I will keep going lower until I feel I am starting to feel weak/drop in power indicating I may have lost too much weight.

I calibrate the Stages before each ride, very quick and easy.
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by BNA » Thu Mar 27, 2014 11:39 pm

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Re: Stages Power Meter

Postby toolonglegs » Thu Mar 27, 2014 11:39 pm

Arlberg wrote:The 360 watts I can only hold for about 12-15 minutes on a climb. My actual FTP over an hour is more like 330.

Might be higher than you think mate... that is a good ride but pacing is all over the place, a well paced 20 or 30 minutes would give you a better idea.
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Re: Stages Power Meter

Postby Alex Simmons/RST » Fri Mar 28, 2014 9:57 am

toolonglegs wrote:Is there a way to check the calibration personally on a stages?.

No, unless you can directly access the torque readings somehow.
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Re: Stages Power Meter

Postby dale79 » Fri Mar 28, 2014 8:13 pm

yes you can directly access the torque readings
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Re: Stages Power Meter

Postby Arlberg » Fri Mar 28, 2014 8:54 pm

toolonglegs wrote:but pacing is all over the place, a well paced 20 or 30 minutes would give you a better idea.


Just curious as to why you think that with the pacing? On Doi Suthep my brief was to ride at a constant 330-340W average and to keep the heart rate as near as possible to just below lactate threshold, which for me kicks in at 167 bpm. That's exactly what happened. The power fluctuations are normal and the overall output average is constant from start to finish, as you can see from the generally horizontal line on the power graph.

The Doi Tung pacing is certainly not as consistent but neither is the incline of that ascent, very hard to maintain a steady wattage output and HR.
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Re: Stages Power Meter

Postby toolonglegs » Fri Mar 28, 2014 11:26 pm

Arlberg wrote:
toolonglegs wrote:but pacing is all over the place, a well paced 20 or 30 minutes would give you a better idea.


Just curious as to why you think that with the pacing? On Doi Suthep my brief was to ride at a constant 330-340W average and to keep the heart rate as near as possible to just below lactate threshold, which for me kicks in at 167 bpm. That's exactly what happened. The power fluctuations are normal and the overall output average is constant from start to finish, as you can see from the generally horizontal line on the power graph.

The Doi Tung pacing is certainly not as consistent but neither is the incline of that ascent, very hard to maintain a steady wattage output and HR.


Slightly OT... better for the training thread, but hey :P .
Your idea of steady pacing and mine ( bottom pic ) is a bit different... and I didn't pace mine very well either. I would think looking at your effort ( on the first link ) that you are spending a lot of time above threshold ( in VO2 effort zone ) which would make you fatigue a lot quicker than if you were sitting right around FTP. Looking at this segment http://www.strava.com/activities/909522 ... 1904255834 ... you average 346w for the first 6km, 325w for the 2nd 6km's. That's a big drop. Personally I can't do steady efforts on climbs...unless they are one or two percent.
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Re: Stages Power Meter

Postby Alex Simmons/RST » Sat Mar 29, 2014 6:08 am

dale79 wrote:yes you can directly access the torque readings

Do they provide the factory calibration slope value to make a comparison with?

I think I read somewhere that the Stages temperature compensation adjusts slope and not just zero offset. Which would make checking slope calibration tricky without precise details of how the temp compensation algorithm works.

In any case, one could use the torque values (units unknown) to come up with a slope value, and then see if that value moves over time.
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Re: Stages Power Meter

Postby Arlberg » Sat Mar 29, 2014 11:41 am

toolonglegs wrote:
Arlberg wrote:
toolonglegs wrote: and I didn't pace mine very well either. I would think looking at your effort ( on the first link ) that you are spending a lot of time above threshold ( in VO2 effort zone ) which would make you fatigue a lot quicker than if you were sitting right around FTP. Looking at this segment http://www.strava.com/activities/909522 ... 1904255834 ... you average 346w for the first 6km, 325w for the 2nd 6km's. That's a big drop.


LT/Anaerobic Threshold for me is 167 bpm. I probably went out a bit hard in terms of power output over the first few kms but I rarely went above LT threshold/Anaerobic threshold the whole climb, and even then only for a few seconds until my HR came back under 167 bpm. Your power graph on that particular ride is certainly more consistent than mine, I think part of the problem with my pacing on that effort was I was using the 30 second power average on the Garmin. I have since switched to the three second average instead which allows for more precise power control.
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Re: Stages Power Meter

Postby Xplora » Sat Mar 29, 2014 2:10 pm

Arlberg, could part of the pacing issue be that you aren't using your best pacing tool? ;)

HR has been abandoned for FTP work because it just isn't responsive enough. If your heart rate has gone beyond LT HR, you've possibly been above LT power for a few more seconds than that... to get the heart rate back under you need to dip below your FTP; this is discounting the possibility that you've overcooked the start of the effort considerably (which seems to be what TLL picked up).

30s is good for keeping your efforts down (prevents overexuberance after a hard initial effort) conbined with instant power or 3s power, but you need that second figure to ensure you keep your effort level up while you gradually return to FTP 30s average power. You might hit the pinch and smash out 600W for 12 seconds, then return to 320W... but your 30s average reads 320, then 360 then 400, then 360, then 320... trying to make that figure say 320 quickly is easy but you'll end up doing 200W instead and that of course is pointless.
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Re: Stages Power Meter

Postby Arlberg » Sat Mar 29, 2014 7:11 pm

Thanks Xplora.

I actually do pace myself now with power rather than HR as you describe. Keep in mind that the Doi Suthep effort was ridden back in October, just weeks after I bought the power meter and before I had learned to use it to its potential.

I now ride/race using FTP and train using HR. For a ride effort such as a TT or hill climb I calculate what wattage I will 'dial in' based on the estimated time the effort will take. As my FTP is 330W, if it's a one hour effort/hill climb I will ride at 330 watts for the duration. If its less than 1 hour then add 1 watt for every minute that the effort is less than 1 hour. eg for a 30 minute effort I ride at 360 watts. A 15 minute effort I ride at 375 watts, a 5 minute effort 385 watts. If its over 1 hour I subtract 1 watt for every minute the duration is longer than one hour. eg A 90 minute effort I will ride 300 watts. Obviously the further the effort deviates from 1 hour the less accurate this method is but generally it seems to work quite well.

And yes I realise its probably about time for another FTP test, but finding a suitable place around Sydney is not easy. Any even slight descent skews the figures dramatically, let alone traffic lights or intersections etc. Might have to wait until i go back to Nth Thailand to 'recalibrate' my FTP.
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Re: Stages Power Meter

Postby Cmm » Tue Apr 01, 2014 7:57 am

Can any one give a definitive answer to if there is a clearance issue when using stages with a giant advanced sl range with an external battery on the chainstay?
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Re: Stages Power Meter

Postby Lukeyboy » Tue Apr 01, 2014 8:08 am

The DI2 battery will pose no issues for stages.
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Re: Stages Power Meter

Postby Cmm » Tue Apr 01, 2014 8:15 am

Thanks! There where reports they would hit each other
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Re: Stages Power Meter

Postby george-bob » Tue Apr 01, 2014 8:32 am

Arlberg wrote:Thanks Xplora.

I actually do pace myself now with power rather than HR as you describe. Keep in mind that the Doi Suthep effort was ridden back in October, just weeks after I bought the power meter and before I had learned to use it to its potential.

I now ride/race using FTP and train using HR. For a ride effort such as a TT or hill climb I calculate what wattage I will 'dial in' based on the estimated time the effort will take. As my FTP is 330W, if it's a one hour effort/hill climb I will ride at 330 watts for the duration. If its less than 1 hour then add 1 watt for every minute that the effort is less than 1 hour. eg for a 30 minute effort I ride at 360 watts. A 15 minute effort I ride at 375 watts, a 5 minute effort 385 watts. If its over 1 hour I subtract 1 watt for every minute the duration is longer than one hour. eg A 90 minute effort I will ride 300 watts. Obviously the further the effort deviates from 1 hour the less accurate this method is but generally it seems to work quite well.

And yes I realise its probably about time for another FTP test, but finding a suitable place around Sydney is not easy. Any even slight descent skews the figures dramatically, let alone traffic lights or intersections etc. Might have to wait until i go back to Nth Thailand to 'recalibrate' my FTP.


If you are interested in a flat spot to do FTP testing: centennial park is good, or Kurnell.

Alex (or anyone who is better at this stuff) is it useful to define a flat and climbing FTP? I can definitely hold a higher power on a climb than I can on the flat, is it useful to define both a flat and climbing FTP?
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Re: Stages Power Meter

Postby earlybird » Tue Apr 01, 2014 9:02 am

Cmm wrote:Thanks! There where reports they would hit each other


On a 2013 TCR Advanced 0 with the battery on the chainstay the stages just touches the battery lever. Nothing that will cause damage to either. However, a couple of bevelled shims fixes it.
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Re: Stages Power Meter

Postby Xplora » Tue Apr 01, 2014 9:04 am

Alex gave me a really good run down of climbing power (particularly with a Q ring) v flat last week. This is his info lol

You slow down your cadence on a hill naturally because inertia has a greater effect on the hill, and as a result you spend a bit more time in the power phase of the pedal stroke. You don't generate that 600w over 360 degrees, so the power meter is making calculations to give you the 600w. Lowered cadence and high inertia on a hill naturally increases the reading. Q ring increases the time spent in the power phase as well, that's the point of the elliptical ring.

I think that you wouldn't calculate a separate climbing FTP but you might adjust your target power to suit the climb. You might give yourself 340w over the climb instead of your FTP of 315w to allow for that difference. Your lactate levels are the same, your power is similar but your PM has a flaw for measuring hill power accurately. I guess my point is that you wouldn't test a separate FTP but don't let your FTP be the sole guide.
Apologies to Alex if something was lost in translation. It makes you realise that making a power meter is very very difficult because you aren't just measuring output on a strain gauge, there is more to it and it has to be super reliable. Made me much much more interested in an SRM when thinking through the implications for training and performance. It never occurred to me that I could be tricking my quarq into false figures :idea: even if they make me feel good :lol:
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Re: Stages Power Meter

Postby boss » Tue Apr 01, 2014 9:34 am

I am waiting with baited breath for Alex to weigh in :D
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Re: Stages Power Meter

Postby Alex Simmons/RST » Tue Apr 01, 2014 9:57 am

Xplora wrote:Alex gave me a really good run down of climbing power (particularly with a Q ring) v flat last week. This is his info lol

You slow down your cadence on a hill naturally because inertia has a greater effect on the hill, and as a result you spend a bit more time in the power phase of the pedal stroke. You don't generate that 600w over 360 degrees, so the power meter is making calculations to give you the 600w. Lowered cadence and high inertia on a hill naturally increases the reading. Q ring increases the time spent in the power phase as well, that's the point of the elliptical ring.

I think that you wouldn't calculate a separate climbing FTP but you might adjust your target power to suit the climb. You might give yourself 340w over the climb instead of your FTP of 315w to allow for that difference. Your lactate levels are the same, your power is similar but your PM has a flaw for measuring hill power accurately. I guess my point is that you wouldn't test a separate FTP but don't let your FTP be the sole guide.
Apologies to Alex if something was lost in translation. It makes you realise that making a power meter is very very difficult because you aren't just measuring output on a strain gauge, there is more to it and it has to be super reliable. Made me much much more interested in an SRM when thinking through the implications for training and performance. It never occurred to me that I could be tricking my quarq into false figures :idea: even if they make me feel good :lol:

You kind of got the jist of it, although the non-circular rings will fool all crank meters (Quarq, SRM etc) in a similar manner, since they all make an assumption about constant crank rotational velocity per revolution when calculating power. The error is exacerbated when climbing as the crank velocity variation per revolution is greater.

Tom Anhalt explained it in this blog post, although it's not a new revelation:
http://bikeblather.blogspot.com.au/2013 ... rings.html


As for hill v flat power, putting aside any power measurement anomalies, that's more a function of several other factors. My power on flats and long climbs is (was when riding competitively) about the same, while for others it can be different and I've known some that can get more power out on flats than on hills. I have my own considered thoughts on it, but I can't point to anything specifically explained by research, probably because it's multifactoral.

Some factors include:
- adaptation to different pedal force - pedal speed scenarios (neuromuscular differences)
- difference in cooling due to large variation in air speed
- tendency of a climb to give much more instant feedback of slowing down than happens on the flat (the mix of dominant resistance forces and their impact on speed for power changes is significantly different)
- higher concentration level required on flatter terrain to keep power up
- small negative gradients on flatter terrain tend to naturally drop power unless you really work hard at it (the same power going down a slight gradient feels way harder to maintain than same power going up a gradient)
- gearing choices / availability
- bike fit / positional differences
- altitude impacts (if high enough)
- and so on...

In the end, if you work at one or the other you'll improve, and if you need to work on one in particular, then do it. On flats it requires greater levels of concentration to keep the strain on the chain.

As for having a different FTP for flats and hills - no.

FTP is an expression of your physiological capability, the fact that a particular scenario means you are not expressing your full capability doesn't mean your physiological capability has diminished simply because the road is flat.

But that doesn't mean that you set yourself unrealistic power targets either, base those on what you can do / have done.
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Re: Stages Power Meter

Postby dale79 » Tue Apr 01, 2014 10:00 am

Cmm wrote:Can any one give a definitive answer to if there is a clearance issue when using stages with a giant advanced sl range with an external battery on the chainstay?


on one of my SL's it cleared but it hit on the other, so I just filed the battery mount on a little angle to move the battery under the chain stay a little more and it is fine now
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Re: Stages Power Meter

Postby Lukeyboy » Tue Apr 01, 2014 7:07 pm

It's a bit of a squeeze but there's plenty of space between the two. The cranks should all be the same but mines a dura ace version.

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Re: Stages Power Meter

Postby dale79 » Tue Apr 01, 2014 7:28 pm

This was mine.. Looks like giant put the battery's where ever they want.. Image
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Re: Stages Power Meter

Postby Cmm » Tue Apr 01, 2014 7:29 pm

Thanks guys!
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Re: Stages Power Meter

Postby Lukeyboy » Tue Apr 01, 2014 8:09 pm

Haha. Who knows what's going on :P What length cranks are you running? I'm running 175's.
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Re: Stages Power Meter

Postby dale79 » Wed Apr 02, 2014 9:01 am

mine are 175's as well..

on my SL0 the battery cleared but my SL3 didn't nothing a file to the mount didn't fix lol
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Re: Stages Power Meter

Postby boss » Wed Apr 02, 2014 10:27 am

Alex Simmons/RST wrote:
Xplora wrote:Alex gave me a really good run down of climbing power (particularly with a Q ring) v flat last week. This is his info lol

You slow down your cadence on a hill naturally because inertia has a greater effect on the hill, and as a result you spend a bit more time in the power phase of the pedal stroke. You don't generate that 600w over 360 degrees, so the power meter is making calculations to give you the 600w. Lowered cadence and high inertia on a hill naturally increases the reading. Q ring increases the time spent in the power phase as well, that's the point of the elliptical ring.

I think that you wouldn't calculate a separate climbing FTP but you might adjust your target power to suit the climb. You might give yourself 340w over the climb instead of your FTP of 315w to allow for that difference. Your lactate levels are the same, your power is similar but your PM has a flaw for measuring hill power accurately. I guess my point is that you wouldn't test a separate FTP but don't let your FTP be the sole guide.
Apologies to Alex if something was lost in translation. It makes you realise that making a power meter is very very difficult because you aren't just measuring output on a strain gauge, there is more to it and it has to be super reliable. Made me much much more interested in an SRM when thinking through the implications for training and performance. It never occurred to me that I could be tricking my quarq into false figures :idea: even if they make me feel good :lol:

You kind of got the jist of it, although the non-circular rings will fool all crank meters (Quarq, SRM etc) in a similar manner, since they all make an assumption about constant crank rotational velocity per revolution when calculating power. The error is exacerbated when climbing as the crank velocity variation per revolution is greater.

Tom Anhalt explained it in this blog post, although it's not a new revelation:
http://bikeblather.blogspot.com.au/2013 ... rings.html


As for hill v flat power, putting aside any power measurement anomalies, that's more a function of several other factors. My power on flats and long climbs is (was when riding competitively) about the same, while for others it can be different and I've known some that can get more power out on flats than on hills. I have my own considered thoughts on it, but I can't point to anything specifically explained by research, probably because it's multifactoral.

Some factors include:
- adaptation to different pedal force - pedal speed scenarios (neuromuscular differences)
- difference in cooling due to large variation in air speed
- tendency of a climb to give much more instant feedback of slowing down than happens on the flat (the mix of dominant resistance forces and their impact on speed for power changes is significantly different)
- higher concentration level required on flatter terrain to keep power up
- small negative gradients on flatter terrain tend to naturally drop power unless you really work hard at it (the same power going down a slight gradient feels way harder to maintain than same power going up a gradient)
- gearing choices / availability
- bike fit / positional differences
- altitude impacts (if high enough)
- and so on...

In the end, if you work at one or the other you'll improve, and if you need to work on one in particular, then do it. On flats it requires greater levels of concentration to keep the strain on the chain.

As for having a different FTP for flats and hills - no.

FTP is an expression of your physiological capability, the fact that a particular scenario means you are not expressing your full capability doesn't mean your physiological capability has diminished simply because the road is flat.

But that doesn't mean that you set yourself unrealistic power targets either, base those on what you can do / have done.


Alex, what Xplora seemed to suggest (at least from my reading) is that power meters read high on climbs (or low on flats) regardless of q-rings or regular rings. Was this a misinterpretation?
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