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-   -   Power Meter (http://www.bikeforums.net/road-cycling/944595-power-meter.html)

TexMac 04-23-14 10:02 AM

Power Meter
 
Anyone with experience using iBike Newton cycling power meter? Good/bad? is it worth it. It's the cheapest out there but not sure.

rangerdavid 04-23-14 10:21 AM

I don't have experience with that one, but I do have a Quarq on my sram red bike, and I'm getting a Stages for my Di2 bike. Can't beat the Stages for light weight, ease of installation and service, and most of all PRICE!!! It's half as much as a quarq.

nhluhr 04-23-14 10:22 AM

It is not a power meter. A power meter measures force and speed and therefore has a direct power measurement. The iBike measures wind, gradient, speed, heartrate, etc and extrapolates power based on certain assumptions. Basically it measures almost everything except power and then makes an educated guess at the actual power.

If you want to have power data for training purposes, it's not the right tool. If you want to have approximate power to tell your friends about, it is probably fine.

zymphad 04-23-14 10:24 AM

Damn, stages for $699 for my 105, that's cheaper than I expected. Though I'm not training for anything. Wonder why some use those bulking SRM when the stages is so small!

bikerjp 04-23-14 10:25 AM

Quote:

Originally Posted by zymphad (Post 16695658)
Damn, stages for $699 for my 105, that's cheaper than I expected. Though I'm not training for anything. Wonder why some use those bulking SRM when the stages is so small!

Might be able to get it cheaper via your LBS. Got mine for 20% off.

nhluhr 04-23-14 10:34 AM

the Stages power meter only measures left leg directly and then doubles the reading to provide total power. This is either "accurate enough" or deficient depending on how you look at it. I'm not saying the SRM is worth it, but it measures both legs and is a full crank.

If you want both-leg full-crank measurement, the Quarq is an extremely competitive option, but of course it's not available in Shimano.

jsutkeepspining 04-23-14 10:46 AM

Quote:

Originally Posted by zymphad (Post 16695658)
Damn, stages for $699 for my 105, that's cheaper than I expected. Though I'm not training for anything. Wonder why some use those bulking SRM when the stages is so small!

SRM's actually measure power, where as stages just measure your left leg power and multiply by 2. Also reliability. My srm was only a bit more for the stages, and it was basically brand new..

bikerjp 04-23-14 11:12 AM

Quote:

Originally Posted by jsutkeepspining (Post 16695730)
SRM's actually measure power, where as stages just measure your left leg power and multiply by 2. Also reliability. My srm was only a bit more for the stages, and it was basically brand new..

The only time the left leg only would be an issue is if you wanted to compare numbers from a Stages to something else and in a rider with a leg imbalance. If comparing to ones own data over time this shouldn't matter much. Injuries would skew data too but aside from that your Stages power number should be a fairly consistent measure and something you can use to train. It just might not mean as much to someone with a different PM. If one could borrow the Garmin Vecto for a couple rides it would be an interesting comparison point as you could ride with both PMs and compare.

Looigi 04-23-14 12:29 PM

...Of course a PowerTap G3 hub is <$800 now so not a bad way to go, especially if you can build the wheel around it yourself.

jsutkeepspining 04-23-14 12:35 PM

powertap > stages.

yeah stages isn't terrible, but why waste that much money on something that only does half the job?

hhnngg1 04-23-14 12:36 PM

Apparently the Stages PM is good enough for pro team SKY this year.

Stages, Wahoo sponsor Team Sky, CycleOps sponsors Trek Pro team, and Team Lampre on ROTOR Power, Movistar on Power2Max | DC Rainmaker

jsutkeepspining 04-23-14 12:38 PM

you give someone money they will ride what every you want. They are also riding pinerellos which are typically heavier and less aerodynamic than other possible bike sponsors.

sijray21 04-23-14 12:41 PM

power2max is a great option for crank-based power meters and it can be pretty affordable. it compensates for temperature drift, options for some cranks with removable spiders, and does L-R balance as well. I'd probably get that over the quarq since it doesn't account for temperature drift and is substantially more expensive.

I don't like the left-balance-doubling Stages, but it is a nice affordable option that doesn't add a lot of weight. no carbon crank options, unless you're willing to mix alloy and carbon for your crank arms.

Bah Humbug 04-23-14 12:43 PM

I'd go with Powertap or Power2Max. Easily.

merlinextraligh 04-23-14 12:44 PM

Quote:

Originally Posted by Looigi (Post 16696096)
...Of course a PowerTap G3 hub is <$800 now so not a bad way to go, especially if you can build the wheel around it yourself.

$889 at Excelsports: PowerTap G3 Hed Belgium C2 Rear Wheel

With the price of Powertaps and Stages, the case for Ibike gets slimmer and slimmer.

Now using an Ibike with a strain gauge based power meter gives you a virtual wind tunnel which could be cool.

Homebrew01 04-23-14 01:09 PM

Quote:

Originally Posted by nhluhr (Post 16695644)
It is not a power meter. A power meter measures force and speed and therefore has a direct power measurement. The iBike measures wind, gradient, speed, heartrate, etc and extrapolates power based on certain assumptions. Basically it measures almost everything except power and then makes an educated guess at the actual power.

If you want to have power data for training purposes, it's not the right tool. If you want to have approximate power to tell your friends about, it is probably fine.

This.

If I had an IBike, I would always be wondering how accurate it really is.

I bought a used wired PowerTap wheel for $250 instead.

bikerjp 04-23-14 01:13 PM

Quote:

Originally Posted by jsutkeepspining (Post 16696107)
powertap > stages.

yeah stages isn't terrible, but why waste that much money on something that only does half the job?

Actually, if you assume a 5% variance in your left/right balance it does 95% of the job.

achoo 04-23-14 01:19 PM

Quote:

Originally Posted by jsutkeepspining (Post 16696107)
powertap > stages.

Not if you ever want to use another wheel for any reason.

Quote:

yeah stages isn't terrible, but why waste that much money on something that only does half the job?
Because it's good enough.

achoo 04-23-14 01:21 PM

Everyone I know who has used an iBike always said they sucked and has always gotten a real powermeter eventually.

nhluhr 04-23-14 01:25 PM

Quote:

Originally Posted by Homebrew01 (Post 16696202)
This.

If I had an IBike, I would always be wondering how accurate it really is.

I bought a used wired PowerTap wheel for $250 instead.

Even worse than its questionable accuracy is its definite lack of repeatability. It requires you to assume certain drag values which are dependent on rider position, clothing, etc, and uses those as part of its algorithm. If you don't wear the same outfit day-by-day then your results would be different each day, making it useless for actual precision training. You'd be better off scrapping the hassle and just going by RPE.

Quote:

Originally Posted by ibike website
Aerodynamic and Frictional Drag Coefficients

As part of initial setup the user enters total bike/rider weight, tire size and road surface, rider height, and ride position. From these inputs the rider’s CdA (coefficient of drag), and bike Crr (coefficient of rolling resistance) are determined.

It's not even using known Cda or Crr values - it's literally guessing based on generalized terms.

TrojanHorse 04-23-14 02:50 PM

It doesn't matter which one you're using, as long as it's repeatable it's perfectly suitable for your purposes, unless you need the highest possible power number to brag about or you want to obsess about leg imbalance.

One thing I dislike about SRM is that you have to send the meter in if you change chainrings. And price, good lord.
One thing I dislike about PowerTap is that you can only use the one wheel. once you start getting multiple wheels you're in a situation where you may as well shell out for a crank based power meter.
Of course, with crank based power meters, now you're limiting yourself to one bike unless you REALLY want to spend some money.

Power2Max seems to be the best over all cost/value solution in today's market with stages & powertap making a similar strong case.

It's not cheap, no matter what you choose, that's for sure. it IS cheaper than it was even 2 years ago though. :)

RChung 04-23-14 03:21 PM

Quote:

Originally Posted by TexMac (Post 16695549)
Anyone with experience using iBike Newton cycling power meter?

I don't have any experience with the Newton but I've examined the output of the previous 3 generations of iBike against PTs and SRMs. Every time iBike has released a new version they claim 1) that it is as good as an SRM or a PT, and 2) that it is an improvement over the previous release.

I've also spent some time examining the Stages compared to various other power meters. Like all power meters, it has good points and not-so-good points. Its data quality is not equivalent to a PT or SRM but it's not bad. I wouldn't use it for QA analyses, or for drag estimation, or for sprint training, but not many people do those kinds of things. Sky probably won't be looking at QA analysis or sprint training, and they can afford to send their riders to the wind tunnel for drag estimation.

lsberrios1 04-23-14 05:20 PM

I'll just say this quick thingy. Without a power meter you are not a real cyclist. And I don't mean Stages, Pioneer, whatever... I mean SRM, Quarq and maybeeeee... power tap. In that order specifically. Good luck!

TexMac 04-23-14 06:00 PM

Quote:

Originally Posted by lsberrios1 (Post 16696907)
I'll just say this quick thingy. Without a power meter you are not a real cyclist. And I don't mean Stages, Pioneer, whatever... I mean SRM, Quarq and maybeeeee... power tap. In that order specifically. Good luck!

Thanks for your input but I was not looking to be a "real cyclist" just a cyclist with a power meter :)

TexMac 04-23-14 06:02 PM

Quote:

Originally Posted by rangerdavid (Post 16695639)
I don't have experience with that one, but I do have a Quarq on my sram red bike, and I'm getting a Stages for my Di2 bike. Can't beat the Stages for light weight, ease of installation and service, and most of all PRICE!!! It's half as much as a quarq.

I have a sram force crank and I was told that stages don't work on carbon cranks


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