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Old 02-09-14, 08:58 AM   #1
karungguni
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Type of Power Meters

Starting to think about power meters. Does anybody have knowledge of using the different types (hub, crank, and pedal)? Will probably be awhile before there are other companies are doing pedal based and prices drop. Interested to hear about real world experience. Am currently building a 2013 Specialized S-Works Tarmac SL4 with components from a crashed 2012 Specialized Tarmac Pro.
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Old 02-09-14, 10:06 AM   #2
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Starting to think about power meters. Does anybody have knowledge of using the different types (hub, crank, and pedal)? Will probably be awhile before there are other companies are doing pedal based and prices drop. Interested to hear about real world experience. Am currently building a 2013 Specialized S-Works Tarmac SL4 with components from a crashed 2012 Specialized Tarmac Pro.
Search is your friend : but in short

Hub : Powertap obviously locked into the rear wheel.. I don't change wheels often so I chose this option on my carbon hoops (Enve 3.4 build)
Crank : Quarq, SRM, Pioneer, Stages(non drive arm)..maybe others…
Pedals: Garmin, Look(polar headunit.. don't think it's ant+)

This guy is always a pretty good read :
http://www.dcrainmaker.com/product-reviews/power-meters
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Old 02-09-14, 10:14 AM   #3
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Search is your friend : but in short

Hub : Powertap obviously locked into the rear wheel.. I don't change wheels often so I chose this option on my carbon hoops (Enve 3.4 build)
Crank : Quarq, SRM, Pioneer, Stages(non drive arm)..maybe others…
Pedals: Garmin, Look(polar headunit.. don't think it's ant+)

This guy is always a pretty good read :
http://www.dcrainmaker.com/product-reviews/power-meters
Subscribe to his feed. Just looking for other's experiences. The negative on the hub is that I just got a new rear wheel. Saw the Quarq on a built up S-Works and peaked my interest again.
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Old 02-09-14, 10:30 AM   #4
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There are other types of PMs than those mentioned. Crank, pedal, and hub systems are what can be called direct force meters, and are undoubtedly the most accurate. Other types might be called power calculators, which include devices like the Cycleops Powercal which calculates power off heart rate, and another category, exemplified by the iBike Newton, might be called oppositional force meters, which measures power based on wind resistance and other quantifiable forces that resist a riders forward motion.

Which system is better for any particular user is a complicated question that depends on various factors like objectives, costs, needs, and so on, to answer. For example, I do my training year-round on a stationary bike with a direct force meter (Cyleops PT300), and also have a Powertap wheel on my spring/winter bike which I use to evaluate my pre-season road riding, but by the time summer rolls around and I'm on my race bike, I use a Powercal because it's light, inexpensive, unobtrusive, provides maximum flexibility, and gives me the general power number that I need for assessing pacing and macro effort.

Once you define your needs and objectives, you can choose a power meter type best suited to them.
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Old 02-18-14, 08:33 PM   #5
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We got my son powertap wheels this past Christmas. Only been riding on a trainer with them but has 200 or so miles on them and really like them I saw the garmin pedals but a msrp of 1700 is very high...would hate to crash on them too. I like the hubs, we got the whole wheelset and once snow melts will be his training wheels. I like hub idea because can always build new wheel with them too.
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Old 02-19-14, 12:04 AM   #6
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Originally Posted by karungguni View Post
Starting to think about power meters. Does anybody have knowledge of using the different types (hub, crank, and pedal)? Will probably be awhile before there are other companies are doing pedal based and prices drop. Interested to hear about real world experience. Am currently building a 2013 Specialized S-Works Tarmac SL4 with components from a crashed 2012 Specialized Tarmac Pro.
A hub works with any crank, and pedals. It can't calculate left/right power. It can swap without tools to any bike using the same wheel configuration, like road, touring, and cross bikes using 700c wheels with rim brakes. Used second generation wired Powertaps which only talk to the little yellow computer can be found for $200 and change if you're really cheap.

A crank works with any wheels and pedals. A 110mm BCD crank would work well for road riding and cyclo-cross with a ring change. You'd be out of luck on your 700C touring bike with a triple crank. Left crank arm versions don't measure total power.

New hub (PowerTap), crank arm (Stages), and crank spider (Power2Max) units are available with similar prices and accuracy.

Pedals work with any crank and wheels. Existing examples use road cleats so you probably won't use them on a cyclo cross bike. Garmin and Polar's prices are painful. Exustar has announced their own podless power measuring road pedal with a projected $1000 price.

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Old 02-20-14, 06:36 AM   #7
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You'd be out of luck on your 700C touring bike with a triple crank.
From the power2max website on the faq page:
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It is possible to build up a power2max as a triple crank set. However, this is only possible if you use a square taper bottom bracket since it allows you to use a longer axle.

I'm not sure if it's worth the trouble for you or not, but there are solutions if you do want a crank power meter with a triple.
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Old 02-23-14, 01:10 PM   #8
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I just purchased a very lightly used wireless powertap 2.4 wheel/head unit last week with a new cluster and decent tire for $400. I am extremely happy with my purchase. It records and downloads power, cadence, heart rate, speed and torque and also nine intervals.
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Old 02-25-14, 06:41 PM   #9
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Pioneer has revamped their crank meter. "Why not give it a try?"

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Old 02-27-14, 12:25 AM   #10
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Something to think about is that the powertab hubs can be used on just about any road bike - the new 11 speed hubs can be used on a 10 speed drive train with a little spacer. I have a slightly older model (whatever was right before G3) and except for the time the batteries died in the middle of a century it's been really solid for me.

But... I have other wheel sets and now I feel like I can't use them or I'll lose out on my power data.

I'm looking for a crank based power meter now and holy crap they're expensive! Power2Max is probably the most reasonably priced one that I've seen, especially if you have a compatible crank already. Quarq is probably the leading candidate for us consumers because you can change chainrings, batteries etc. on the newer models without sending the whole crank in for service. Let that sink in for a minute. I believe P2M is the same but SRM is very user-unfriendly in that regard. For cranks, you also have the varying BB standards to deal with (really just 30mm and 24mm axles) and whether you want 130 BCD or 110, so there are potential compatibility issues and again, you're locked into one crank.

So, if you ride one bike all the time and like to change wheels - get a crank power meter.
If you ride different bikes and might swap the wheelset between them, powertap.
If you only intend to have one bike with one wheelset, either will work fine.
Pedals will give you the most flexibility of course.

PS I completely forgot about Stages because I'm a kind of one-legged power generator but if you are mostly normal in both legs that's a perfectly viable alternative. Checkout DC Rainmaker's reviews for detailed info, he seemed to think they worked just fine.
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Old 03-02-14, 07:59 AM   #11
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But... I have other wheel sets and now I feel like I can't use them or I'll lose out on my power data.
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Pedals will give you the most flexibility of course.
I'd argue the iBike Newton is the most flexible power meter out there because you're not locked into anything other than having a handlebar or stem to mount it to! Both the pedal systems lock you into 3 bolt cleat systems and shoes, and the Look further locks you into the Polar protocol.
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Old 03-02-14, 11:59 AM   #12
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I'd argue the iBike Newton is the most flexible power meter out there because you're not locked into anything other than having a handlebar or stem to mount it to! Both the pedal systems lock you into 3 bolt cleat systems and shoes, and the Look further locks you into the Polar protocol.
That's expensive too... 500 for the unit and you're up to almost 800 by the time you add in the HR strap and software. It seems to be a real trial to set up and nobody has really come out and said "yep, this is for me" (that I found in my limited search time). Obviously it's all estimates, as opposed to measurements. All I have to do to get my power tap set up is spin the wheel to start the thing up. Easy.

No cheap answers, that's for sure.
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Old 03-02-14, 05:46 PM   #13
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I'm a nerd, what can I say.




That's expensive too... 500 for the unit and you're up to almost 800 by the time you add in the HR strap and software. It seems to be a real trial to set up and nobody has really come out and said "yep, this is for me" (that I found in my limited search time). Obviously it's all estimates, as opposed to measurements. All I have to do to get my power tap set up is spin the wheel to start the thing up. Easy.

No cheap answers, that's for sure.
iBike say emphatically that Newton measures power; it does not estimate it.

No, the Newton was not 'for me' either (my coach has one, though), but flexibility is independent of ease-of-use, and Newton is the most flexible.
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Old 03-02-14, 06:05 PM   #14
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iBike say emphatically that Newton measures power; it does not estimate it.
They're emphatically wrong then. They're calculating power based on other measurements perhaps (but not directly measuring it!), but I don't need to weigh myself, my bike & my water bottles to use a power tap.
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Old 03-03-14, 05:06 AM   #15
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They're emphatically wrong then. They're calculating power based on other measurements perhaps (but not directly measuring it!), but I don't need to weigh myself, my bike & my water bottles to use a power tap.
This gets into deep questions about what defines estimate, calculation, and measurement, and really the only distinction is certainty, which most fields try to address through precision.

I think, though, that measuring force directly is not possible, and we always have to measure it as it acts on something. In the case of crank power meters, force is not measured directly, but calculated through the behavior of metal subjected to it combined with angular velocity Strain gauges themselves must be calibrated with knowledge of how the host material behaves under force. This is why we don't see carbon fiber hosting strain gauges, because its behavior under force is inconsistent.

The Newton measures not metal deflection, but oppositional forces like air pressure to calculate force. iBike cleverly named their meter Newton in hopes it may trigger your recollection of the famed mathematician's 3rd Law of Motion.

So pick your poison, I guess, because if you want to calculate force, you'll have to measure something else first. Of course not all measurements are equally precise, and at some level of imprecision we have to call it a guess. Looking at The Newton's results and comparing to other types of power measurement, it's clearly not guesswork.
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