# best power meter for my dogma?



## Donn12 (Apr 10, 2012)

Which one is the best and why? I have zipp 303s, campy SR EPS and I find myself leaning towards a PM for the rear hub for some reason. any advantages to this or something else? I don't really want the campy crank setup for $2k +. It seems like new designs are starting to come out so I think in a couple of years power meters are going to be cheaper and more popular .

Also - I like the sound the zipps make when freewheeling because they are very loud and it gives people I am approaching a heads up without me doing anything


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## looigi (Nov 24, 2010)

Garmin Vector pedals if you're OK with Look type pedals/cleats.


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## mikerp (Jul 24, 2011)

P2Max and SRM would be a drop in and you would have spare cranks if you needed something serviced, but as you mention they come at a cost.

If you like the Zipp sound the hub solution is off the table.

That leaves a pedal solution Look or Garmin (as mentioned by looigi)


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## g-Bike (Jan 25, 2006)

*SRM with UCB (User changeable battery) IS the way to go.*



mikerp said:


> P2Max and SRM would be a drop in and you would have spare cranks if you needed something serviced, but as you mention they come at a cost.
> 
> If you like the Zipp sound the hub solution is off the table.
> 
> That leaves a pedal solution Look or Garmin (as mentioned by looigi)


--- Go with an SRM and only spend your money once. They are and will be for sometime the gold standard in durability / reliability as well as accuracy. I am on my 2nd unit, one on the road bike, now one with UCB on the CX bike and soon one for the mtn bike. Buy it and spend time riding not sending it back for service or warranty issues. The new UCB lasts 4,000 hours of use, no other manufacture can come even close. Check them out at Home or if you are at Sea Otter this weekend come by the booth. Be well.


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## LouisVuitton (Aug 31, 2009)

Do not waste money on an SRM. They are overpriced, not worth the money, and do not even have a battery that you can replace yourself. 

Go with a PowerTap hub or the Garmin Vector pedals-based power meter if you're running Campy. If you were running Shimano or SRAM, then I would then recommend the crank based Quarq which is a way better way to go than the SRM and just as accurate. 



g-Bike said:


> --- Go with an SRM and only spend your money once. They are and will be for sometime the gold standard in durability / reliability as well as accuracy. I am on my 2nd unit, one on the road bike, now one with UCB on the CX bike and soon one for the mtn bike. Buy it and spend time riding not sending it back for service or warranty issues. The new UCB lasts 4,000 hours of use, no other manufacture can come even close. Check them out at Home or if you are at Sea Otter this weekend come by the booth. Be well.


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## mikerp (Jul 24, 2011)

LouisVuitton said:


> Do not waste money on an SRM. They are overpriced, not worth the money, and do not even have a battery that you can replace yourself.
> 
> Go with a PowerTap hub or the Garmin Vector pedals-based power meter if you're running Campy. If you were running Shimano or SRAM, then I would then recommend the crank based Quarq which is a way better way to go than the SRM and just as accurate.


You missed his point, with SRM you don't spend time changing the battery due to the battery lasting for (claimed 4000 hours). With Powertap I seemingly find myself changing batteries a good deal (upgraded firmware last night and swapped battery as it went dead on a ride). I'll see how the P2Max goes with batteries when I get one (next month if the Campy cranks are ready). I'll have 3 systems at that point.


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## spade2you (May 12, 2009)

Quarq? I have a Sram crankset with Rotor 10.5 speed rings. Works just fine with my Campy components. I didn't like how much the SRM costs.


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## Cinelli 82220 (Dec 2, 2010)

mikerp said:


> That leaves a pedal solution Look or Garmin (as mentioned by looigi)


Look comes bundled with Polar head unit and is a PITA to set up and run.

The Garmin is a much better option.


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## spdntrxi (Jul 25, 2013)

Cinelli 82220 said:


> Look comes bundled with Polar head unit and is a PITA to set up and run.
> 
> The Garmin is a much better option.


yes garmin by a mile ... look is locked into polar.


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## mikerp (Jul 24, 2011)

LouisVuitton said:


> If you were running Shimano or SRAM, then I would then recommend the crank based Quarq which is a way better way to go than the SRM and just as accurate.


Forgot to bring this up earlier Quarg claims +/- 1.5%, SRM less than +/- 1%. Most mortals won't be able to tell the difference but one is clearly more accurate than the other. From memory SRM uses 8 strain gauges Quarg and P2M use 4. I'm not sure if SRM has some corrections in their software to make adjustments if a gauge starts to fail (you can interpolate with 8 gauges in a circular pattern - you can't do it with less).


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## rchung (Apr 19, 2009)

mikerp said:


> Forgot to bring this up earlier Quarg claims +/- 1.5%, SRM less than +/- 1%. Most mortals won't be able to tell the difference but one is clearly more accurate than the other. From memory SRM uses 8 strain gauges Quarg and P2M use 4. I'm not sure if SRM has some corrections in their software to make adjustments if a gauge starts to fail (you can interpolate with 8 gauges in a circular pattern - you can't do it with less).


It's not quite that simple: some models of the SRM use 16 strain gages, others use eight. In the past, some older SRM models used as few as two while the old "Scientific" model had 20. The Quarq currently uses five, but in a particular orientation. The Power Tap has eight, the Power2Max uses four. In all of these cases, as long as the "rosette" of strain gages are properly designed, what determines accuracy and precision isn't the raw number of gages (btw, it's an historical oddity that it's spelled "gages" and not "gauges") but the stiffness of the thing they're mounted onto: SRM uses 16 gages on some cranks because they're not as stiff as the ones they put eight on, and SRM has admitted that if accuracy and precision are essential then some of their crank models are to be preferred over others. In addition, there's a separate issue about temperature compensation which, again, isn't exactly dependent on the raw number of strain gages. Bottom line, the world would be simpler if you could just say "this PM has more strain gages than that one so it's more accurate". Accuracy and precision are more complicated than that.


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## Dunbar (Aug 8, 2010)

mikerp said:


> With Powertap I seemingly find myself changing batteries a good deal (upgraded firmware last night and swapped battery as it went dead on a ride).


My G3 batteries last about 100-120 hours of riding. Obviously longer is better but the hardest part about changing the battery is removing and reinstalling the rear wheel. The main disadvantage of Powertaps are they lock you into using one wheel set (unless you install one on every wheel set you own.) I can pretty much guarantee the OP won't want to train without power after they start using a PM.

Power2Max and Quarq are more reasonably priced than SRM if the OP isn't opposed to running a non-Campy crank.


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## tom_h (May 6, 2008)

PMs being so expensive, it behooves OP to join the Google "Wattage Forum", where there is a trove of experience concerning PMs, before dropping $800-2500 on a PM.

An excellent overview of PMs at:
Alex's Cycle Blog: Which power meter?
I believe Alex Simmons is also one of the moderators at "Wattage".

IMO, the only "proven" and reasonably mature PMs at this point are:
SRM, Powertap, and Quarq.

Garmin pedals are still on a steep learning curve, and installation can be tricky to ensure correct & accurate calibrations.

About a year I ago I installed a Quarq Riken PM on my otherwise Chorus 11 drivetrain.

I was _not _totally happy with the SRAM chainring shifting -- fewer pins & ramps than Campy rings -- and front shifting was a little slower & less precise.
However, I recently installed WickWerks rings and IMO they shift as well, maybe a little better, than Campy. 

With the latest v21 firmware update, my Quarq Riken has been rock-steady on zero offset drift -- what Garmin head units erroneously call "calibration".
Typically I only get 10-12 point ZO drift before, during, and after 3+ hr rides -- equivalent to a 3-4 watt drift @ 90 rpm.
Quite negligible drift, although I typically will zero the PM before a hill climb interval, anyway.

BackCountry.com has 20% off sale valid thru Sunday April 13, so consider pulling the trigger on a PM from them.
power meter - Search Results | Backcountry.com

The Quarq & Powertaps PMs are eligible for the discount, Garmin & SRM are _not_.

Rash decisions are rarely a good idea, but if the PM is new and unused, you can return it for a refund if you change your mind later in the week.


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## Donn12 (Apr 10, 2012)

I am leaning towards the garmin pedals. seems like the best solution for me. i don't want to change my crank arms and i have to many bikes for a power tap..


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## tom_h (May 6, 2008)

Donn12 said:


> I am leaning towards the garmin pedals. seems like the best solution for me. i don't want to change my crank arms and i have to many bikes for a power tap..


You should definitely subscribe to the Google "Wattage" forum ... you will find tips on how to setup the garmin pedals ... the pedals do have some quirks, but IIRC none of the quirks seem fundamental or insurmountable.

If you dont already have a good quality torque wrench, you'll probably need one for the garmin pedals, they seem sensitive to it.


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## looigi (Nov 24, 2010)

Another very good source of info on PMs is: Power Meters | DC Rainmaker

Also, his "in depth" review of the Garmin Vector PM pedals: Garmin Vector In-Depth Review | DC Rainmaker

...if it hasn't been mentioned already.


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## Jay Strongbow (May 8, 2010)

Out of curiosity does anyone know if pedal power meters can tell the difference between pressure that results in power getting to the back wheel and power that doesn't?
In other words would standing put not actually pedaling going over a washboard or not unweighting on the upstroke register as power?


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## Dunbar (Aug 8, 2010)

Jay Strongbow said:


> In other words would standing put not actually pedaling going over a washboard or not unweighting on the upstroke register as power?


All power meters need to measure torque and cadence. You can have torque but if cadence is 0 than power would be 0 watts. Think track standing at a light, power would be zero if you're stationary. I'm not clear on the scenario you're asking about but if you have torque and cadence >0 it would register some power.


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## Jay Strongbow (May 8, 2010)

Dunbar said:


> All power meters need to measure torque and cadence. You can have torque but if cadence is 0 than power would be 0 watts. Think track standing at a light, power would be zero if you're stationary. I'm not clear on the scenario you're asking about but if you have torque and cadence >0 it would register some power.


ah, makes sense. Thanks.


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## looigi (Nov 24, 2010)

Yet another reason for one to pay or have paid attention in their high school physics class.


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## tom_h (May 6, 2008)

Jay Strongbow said:


> #1 Out of curiosity does anyone know if pedal power meters can tell the difference between pressure that results in power getting to the back wheel and power that doesn't?
> #2 In other words would standing put not actually pedaling going over a washboard or
> #3 not unweighting on the upstroke register as power?


Three questions --

#1  No, it cannot, Garmin pedals will only msr power delivered to the pedals. Similarly, a crank PM (Quarq, SRM) will only measure avg power applied to the crank.
A reasonably clean & lubed drive train will have ~2% or less power losses from crank to rear wheel.

#2 And as stated above, Power = Torque x RPM x (fixed constants).

#3 Weighting down the pedal on the rear _upstroke_, is defined & interpreted as "negative" torque by the crank & pedal PMs.
The neg torque subtracts from the "positive" torque on the other leg's downstroke. Net effect, less average power applied to the crank.

There have been a number of exercise physiology studies on "pedaling styles" over the years. One measured that the best TT racers, when using their "preferred" pedaling, actually did not fully unweight the upstroke leg, ie there was some neg torque on the up leg. They just pushed harder on the down leg.
There are some interesting nervous system peculiarities involved.


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## looigi (Nov 24, 2010)

Check this: PezCycling News - What's Cool In Pro Cycling : Pioneer’s Power Meter Advances Pedaling Analysis









It's important to understand that useful torque is due to the component of the force vector that is tangential to rotation. The radial component does no useful work, though it does consume rider energy. 

I'll just mention that for training purposes, the point is to measure the effective relative effort/power produced by the rider. Efficiency of the drive train is pretty much irrelevant as is absolute accuracy. Accuracy can be useful though in that it allows comparison between PM devices.


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## g-Bike (Jan 25, 2006)

*Are you sure Here is the SRM FSA 386 User Changeable Battery System*

SRM PowerMeter FSA K-Force BB386 UCB






LouisVuitton said:


> Do not waste money on an SRM. They are overpriced, not worth the money, and do not even have a battery that you can replace yourself.
> 
> Go with a PowerTap hub or the Garmin Vector pedals-based power meter if you're running Campy. If you were running Shimano or SRAM, then I would then recommend the crank based Quarq which is a way better way to go than the SRM and just as accurate.


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## Donn12 (Apr 10, 2012)

I just found this ....maybe the is version will have the loud hub I want? if so i could maybe convert my trainer bike to campy 11 (I would save $600 vs garmin pedals) and then be able to move this between 2 bikes with the rear wheel vs switching pedals. I would skip power meter for MTB and CX


PowerTap GS Hub PowerTap GS Hub PowerTap GS Hub PowerTap GS Hub PowerTap GS Hub PowerTap GS Hub
POWERTAP GS HUB
Title

Qty: 
Price$1,089.99
PERFORMANCE. TECHNOLOGY. GS.

Industry-leading power accuracy wrapped up in a bomb-proof hub shell.

With the expertise of 15+ years of power measurement, PowerTap looked to DT Swiss and their renowned reputation for quality and performance to join efforts in creating the PowerTap GS.

The GS is everything you'd expect from a PowerTap hub, with the added bonus of the DT Swiss Ratchet System™ technology. From the press fit assembly with contact-free seals, to the DT Swiss bearings to the exchangeable rotor body, every DT Swiss hub is designed to transform a rider's energy into forward momentum. Combine PowerTap's +/- 1.5% accuracy with ideal strength to weight ratio and straight-pull spoke technology, you'll get a stiffer, more responsive, and better riding wheel.

- See more at: PowerTap GS Hub by PowerTap | PowerTapÂ®


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## tom_h (May 6, 2008)

Donn12 said:


> I just found this ....maybe the is version will have the loud hub I want?
> PowerTap GS Hub PowerTap GS Hub PowerTap GS Hub PowerTap GS Hub PowerTap GS Hub PowerTap GS Hub
> POWERTAP GS HUB
> Qty:
> ...


Nearly $1100 for _hub only ?!_
It will be in the high $1000s by the time you build a wheel using comparable components, probably over $2K if you lace another Zipp rim to it.

DT Swiss hubs _are _loud, but that's a lot to pay to just to get loud.

Had you acted on the Backcountry.com discount, you could have had Quarq Riken (crankset) PM for under $1300, and used it with any wheelset,including the very nice Zipp 303 that you already own.


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## Donn12 (Apr 10, 2012)

I was planning on putting it on the wheel I already have not another one...is that a bigger deal than I realize? I don't really have any interest in anything besides one of these or the pedals. I would prefer this because I can move to from bike to bike by just changing the rear wheel. It will be interesting to see what comes out down the road though!


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## tom_h (May 6, 2008)

Donn12 said:


> I was planning on putting it on the wheel I already have not another one...is that a bigger deal than I realize? I don't really have any interest in anything besides one of these or the pedals. I would prefer this because I can move to from bike to bike by just changing the rear wheel. It will be interesting to see what comes out down the road though!


No, not a big deal.

If you're going to go that route, and depending on where you live, you may want to check out wheelbuilder.com in So Calif. They have a very good reputation, although I've never had any reason to use them.

For some different scenarios, read:

Zipp PowerTap Wheels - Wheelbuilder.com

Zipp PowerTap Wheel - Wheelbuilder.com

PowerTap Wheel Carbon Rim Upgrade (Using Your Own PowerTap) - Wheelbuilder.com


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## g-Bike (Jan 25, 2006)

Which ever device you chose I say spend your money locally. Yes you can save 10-20% on-line and if it is worth that saving to undercutting your local bike shop and employees then go for it. You seem to be someone who has the ability to spend their money as they like and spending it locally makes more of an economical difference then the small amount of savings by shopping on-line. Just a thought...


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## Donn12 (Apr 10, 2012)

All my purchases go through my LBS with the exception of campy parts. If my LBS has any financial problems it is definitely not because of me! They did tell me that the shimano stuff is so cheap they are using that more than ever.


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## MMsRepBike (Apr 1, 2014)

Team Sky knows what they are doing.

Head to your local Pinarello dealer and buy a Stages Power Meter.


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## tom_h (May 6, 2008)

MMsRepBike said:


> Team Sky knows what they are doing.
> Head to your local Pinarello dealer and buy a Stages Power Meter.


More probable that Stages gave Sky a big $$ sponsorship deal.

Obviously marketing works -- you're advising OP to not waste a minute on a non-Stages PM!

Anyway, the OP has stated he's leaning toward the Garmin PM pedals.


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## MMsRepBike (Apr 1, 2014)

tom_h said:


> More probable that Stages gave Sky a big $$ sponsorship deal.
> 
> Obviously marketing works -- you're advising OP to not waste a minute on a non-Stages PM!
> 
> Anyway, the OP has stated he's leaning toward the Garmin PM pedals.


I read the press article, it was Sky that approached Stages. More specifically it was the mechanics from Sky that were fed up with SRM and wanted a better and easier option. 

Garmin is way overpriced and a HUGE pain in the arse.

Stages is cheap, effective and it's just a non-drive crank arm. So easy to swap between bikes. Crank and hub power meters are too much trouble. Garmin is way too clunky and expensive. 

Stages is what I run, what all of my friends run, what my shop sells the most of and what I predict the masses will all be on soon. It just makes sense.


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## tom_h (May 6, 2008)

MMsRepBike said:


> ... Garmin is way overpriced and a HUGE pain in the arse. ...


 Unfortunately it didnt meet the original Metrigear target of a $1K price point ... and install does seem a bit more fussy.



MMsRepBike said:


> ... Crank and hub power meters are too much trouble. ...


yeah, because swapping a wheel is SO hard and takes SO long :sarc:
If you take off the Stages left crankarm, you've done virtually all the work needed to swap a crank. Literally less than an extra minute, you can remove the entire crankset, and swap a Quarq or SRM to another bike.




MMsRepBike said:


> ... Stages is what I run, what all of my friends run, what my shop sells the most of and what I predict the masses will all be on soon. It just makes sense.


 So you have a $$ incentive to push Stages...
Might also be a regional thing. What I see most of in SoCal is powertaps and crank-based (mostly Quarq, some SRM). 

IMO the biggest issues with Stages are,
- not available with any carbon crankarm AFAIK.

- there isn't any _independent _evidence that a _left-leg-only_ PM will be repeatable over longer periods, or with varying levels of fatigue, or varying levels of power output.

-In fact there is some independent evidence the left-leg-only concept can lead to some large errors: On Bicycles, and.... what else is there?: Sky switch from SRM to Stages


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## Donn12 (Apr 10, 2012)

I changed to a power meter and it should show up any day now. I will be able to swap from bike to bike pretty easily.....crankarm is a no go for me because of that


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## g-Bike (Jan 25, 2006)

The rumor is that most of those Stages units are not even working correctly. Spend your money once and ride your bike more.


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## g-Bike (Jan 25, 2006)

Glad to hear you got it sorted out. Enjoy.


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## mikerp (Jul 24, 2011)

MMsRepBike said:


> I read the press article, it was Sky that approached Stages. More specifically it was the mechanics from Sky that were fed up with SRM and wanted a better and easier option.


Please post a link to the article, my google skills must be lacking as I haven't found it.

BTW, the OP can't use a Stages on his Dogma as he is running Campy as he should be with his Italian frame. Before you start promoting something you might want to check if it will actually work for them. You aren't really suggesting that the OP remove his Campy SR cranks and buy a Durace Crank just to use Stages?
It doesn't even make sense from the crank end.
Crank Review #5 - Fair Wheel Bikes
let alone the cost end.


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## cxwrench (Nov 9, 2004)

MMsRepBike said:


> Team Sky knows what they are doing.
> 
> Head to your local Pinarello dealer and buy a Stages Power Meter.


This question has nothing to do w/ Stages. Why are you telling the OP to "head to your local Pinarello dealer and..."? What does Pinarello have to do w/ Stages? Your advice seems to get stranger and stranger as the days go by. 

Not to mention the fact (already pointed out by others) the OP has Campy on his bike.


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