ibike Power meter - Page 3

Though it's nice that the numbers were close, if you weren't riding side-by-side for the entire time (and you said that you weren't), then it's not a valid comparison. Also keep in mind that 0.04 and 0.08 W/kg can be a reasonably significant number of Watts in some contexts.

I have been using an iBike on daily commutes and training rides for over a year. I am on my second unit as I believe that the first one demonstrated some technical issues and was never properly functioning. I ride PowerTaps on my road bikes and decided to try an iBike on my commuter.

The iBike is a functional but truly quirky unit, that eats batteries and requires daily and often an as-you-ride calibration effort by comparison. I know guys who profess to buy their batteries for these units in blocks of hundreds. Riding the unit this winter on commutes, I could easily go through a battery every few rides. In some of the coldest conditions (for my part of North Texas) I would even be needing to make battery changes during my long rides.

Here is a brief description from an iBike user of what the manufacturer will agree that you will likely need to look at or do each time you ride:

Before each ride starting from home, I:

(1) Weigh myself, with bike and equipment, and enter the value in
Set Up;*
(2) Perform a tilt calibration; and
(3) Zero the wind off-set (a step which, I've discovered, is
extremely important for accuracy).

* When I ride home from work, I usually omit the weigh-in and
assume that my morning weight is "close enough."

In neither case do I perform a coast-down as part of my routine.
Just as John Hamann had assured me, since installing a standard
mount several weeks ago, I've seldom needed to do a new coast-down.
Any inaccuracies that I've experienced during that time have seemed
attributable to (a) cold weather; (b) failure to calibrate tilt
(particularly when removing and replacing the unit on its mount);
or (c) failure to zero the wind offset (particularly following
changes in weather). Hence the set-up routine above. When I do
follow this routine, however, my unit's readings are consistent and
seemingly accurate.


The biggest issue that I find in terms of data reliability is the unit's tendency to produce psychotically incorrect power spikes. Even with all the firmware updates and recommendations for use this is still an issue. The result is that these spikes dramatically skew your power numbers and related training calculations, especially when you use CyclingPeaks. Just a couple of these spikes a ride can really mess up your overall power profile. One time your max power output may be 1200 watts, another time it could be 2200. There is no rhyme or reason to it. But there is sure no way to train with that kind of screwed up data effect. The unit still has issues over rough roads too, which goes a long way to hender its inherent ability to translate rides into usuable and repeatable ride data. Take a look at the iBike forums and see what you think about the comments from some of the other users though, and gauge what you can live with on your type of intended rides.

The main frustration that I have had in all of this though is that for $400 a power device damn well better work the way that it says it will, and without a lot of calibration, on the bike and off the bike guess work and data interpellation. That has not been the experience with the iBike. Most of what you would now be using as guidelines for utilizing this device came from on the road users, not from the manufacturer, and apparently will continue to be so down the road. There are an amazingly large bunch of user who apparently don't have anything better to do than to do pro bono R&D for these iBike units. Truthfully, I am not one of them. If you are, you may well love this unit for that same reason.

My overall reaction to a properly functioning iBike Pro unit is that they don't perform nearly as easily and consistently as does a PowerTap. On the PowerTap you set it up, zero out the torque, and you get your ride data. Clearly PowerTaps can have torque tube issues, manufacturing defect issues, issues with keeping out the wet, and installation do's and don'ts too. Nevertheless, they are a ride-and-use device, without a lot of intrigue or voodoo. If you ride a lot, you will likely go through HR strap batteries every few months, a CPU battery a couple of times a year, and hub batteries about once a year. There really isn't much that you can do to influence the data output except via your pedals. And after a few years of training with a PowerTap, I can consistently guess within 10-15 watts of what I am generating just about every mile of a ride, solo, group, paceline, climb, you name it. The data it generates is that consistent, and lends itself well to that kind of on-the-road interpretation and repeatability.

Again though, everybody's training conditions, methods and expectations aren't the same though. The best advice that I can give is for you to do your homework and spend your money based upon what you can live with.

Now I have to go pee.

__________________

First, let me say that I admire the ingenuity and creativity of the team that created the iBike. I think everyone benefits when there is an expansion of possibilities and competition of ideas. I also like the possibility of roll-down aero testing.

That said, the issue of accuracy under all conditions (in a pack, out of a pack, certain situations that might through it for a tizzy such as Gene mentioned) is a big deal for me. When you consider that:

• most of us are looking at FTP improvement over the course of a year of probably <10% (mine usually changes less than 10% over the course of the year because I've been at this game for a while) and that week-to-week improvements are often in the single Watts, Power Tap's stated accuracy of 1 - 1.5% looks very attractive.
• as a racer, I have little control over the amount of people that I ride with
• I ride with various hand positions and in a fully aero position on a TT bike
• errors will accumulate over time and tend to make WKO+'s PMC less accurate

then I have big problems with the iBike for my own use, but "your mileage may vary", as they say.

Does anyone have any data on repeatability and reproduceabilty on an iBike, even under ideal conditions and also on a roll-down test?

What's so amazing to me is the "your power meter sucks and mine is the only choice" mentality of most iBike naysayers.

Many of the complaints that are levied against the iBike (i.e., flaky data, reliability issues, eats batteries, et al) have been levied against every power meter that riders discuss on this forum. My god how many my PT doesn't work posts have I seen in the past two weeks?

I've had one iBike unit, change the battery every 5 weeks, do a coast down and go. I don't need laser precision to train with power and to say that one can't measure/manage their training with an iBike is disingenous or an opinion born out of ignorance.

Insofar as "real cost" is concerned the comment about not having heartrate and having to buy sw is also misleading. It doesn't have HR today (and personally I don't want it even when they do release it) and when they do it probably means I have to purchase an $ 89 mount. On the software issue are not most using Cycling Peaks? So for $ 99 more I've got that solved.

I'm not sure why iBike bashers are so afraid of this little device/company. It makes no sense.

gene r

Gene,

Pointing out flaws is part of healthy discussion. If you wilt under hot lights, that's not our problem. It doesn't mean I hate you or the iBike.

In my job as an engineer, if I did not evaluate options based upon data, trade-offs, accuracy, cost and a whole host of other things, I would not have lasted 20 years in the electronics industry. I would have been out on my ear a long time ago. While not all decisions in my personal life require the same level of scrutiny (or accuracy) as what I do at my job, blindly accepting marketing spew would seem to be a perilous course to take too. When you're going to plunk down a few hundred to several thousand $ on something, spending some time finding out the real pluses and minuses from real people would seem to be an intelligent course to take.

I also didn't say you can't use it. I simply said I had my reasons why it doesn't seem suitable for me. Consider the meaning of "your mileage may vary" one more time. Also, scroll up a little and you'll also find that I stated, "PT and SRM users have enough problems as it is..." Consider the meaning of that too.

What I also think is interesting is that the tech person (sorry-I for got his name) I spoke to yesterday was very frank and said there will be times when the iBike will drive you nuts!!


he offered some other interesting thngs that you can do with an ibike that you cannot do with a PT< SRM< Ergo. You can (in very perfect conditions!!) do coast down tests to determine advantages in any number of different things from position to air pressure, tires, wheels, aero bars, clipons, elbow pad width, etc.
Also, it is possible while drafting in a pack to use the data on screen to find a spot in the draft that provides the least wind resistance. This could be helpful while riding into cross winds (to establish the best direction or angle for the echelon to take).

For a real bike geek (not an insult) with more time than most of us have, this could be a really fun toy!!

Ray

Not wilting (or taking this personally), I just feel that some of the comments about the iBike misrepresent the efficacy of the device vis-a-vis other offerings in the space. I've also said all along that YMMV and that the iBike is not for everyone.

gene r

Hey, exactly ray! I can see that a lot of iBike users are really enjoying tinkering around with their units, mounts, and uses. A lot of what they are doing is pretty passionate and inspired.

And gene, truth is that you can take an iBike, go ride it on chip and seal, over rough road, in a pack, or in high cross wind situations with a lots of cornering and get complete shiznit for training data. If iBike had done a much better job of being upfront about the issues with their units, I think that a lot of the user commentary that they get in these threads would be more forgiving.

The smart money may well be to wait until the iBike Pro 2 or future version comes out that takes all of the current user R&D into account. That unit might stand to do a lot of things better than does the current unit.

__________________

You can do that with a power meter, not just the iBike. I did this recently while riding in echelons in Arizona (with a Power Tap).

One potential benefit of iBike, regardless of it's efficacy as a training tool, is that it may cause others to enter they fray and offer more reasonably priced alternatives. Let's face it, measuring torque isn't new technology, it's just found a new application. Personally I think the prices for a PT is a way to high.

Maybe a price correction here will lead bike companies to start offering PM's as standard on higher-end bikes. That would be nice......

Hmmm. What makes him [edited from: you] think you can't do these things with a PT, SRM, or Ergomo?

With a power meter, you have to do this on a flat, straight road in windless conditions. You can't do it as a roll-down (i.e., roll down a hill with no pedalling required) because you have to supply power to "the system" to measure something on the power meter. Because the iBike inherently works off air flow, you can do this as a roll-down test. Again, you need windless conditions for it to work out.

Of course, you could always do a roll-down test with no meter, just a stopwatch or a riding buddy to use as a control (old school) but the accuracy, resolution and repeatability would probably be a lot worse than with an iBike or a power meter.

There are a lot more short hills to roll down than flat roads around here, for sure. I know of only one flat, straight 1 km section of paved path in a 30 mile radius of me.

Any time you estimate something rather than directly measure it, you are introducing another set of variables that can produce even more error. People with Power Taps and SRMs have enough issues as it is, why make things more difficult on yourself? And don't try to tell me that you are measuring torque with an iBike because you are not.[/QUOTE]

• All power meters estimate power it cannot be directly measured. It doesn't matter whether you measure material strain and calculate torque and hence power or measure opposing forces it's the same. The iBike will give very similar result to an SRM or Powertap. Only in extreme conditions will the unit be off (severe crosswinds and moving around in a small pack). Most of the time it is bang on.

__________________

I think there's something being lost/garbled in translation. When I've talked to both John Hamann and Glen Cunningham, the developers of the iBike, they've both been very upfront and honest about the strengths and limitations of their product. They believe in it and don't feel the need to "spin." Curiously, the website gives a different impression. I don't know why the discrepancy.

RE using the iBike for aero testing: some of us on the iBike list have been trying to establish the precision of the device by doing multiple coastdown tests and comparing the results. We're also trying to see how different procedures and conditions affect the variability. My testing found a standard deviation of about 2% in CdA and 6% in Crr. I also found that the two vary oppositely. This was under non-ideal conditions, with a variable 5-12mph breeze. Since coastdown tests are fairly quick to do, I do multiple ones and average them to increase precision. (In fact, I'd recommend multiple coastdowns to anyone wanting real accuracy out of the device.) After a lunchtime's worth of testing, I believe I got both numbers to within 1%.

RE finding the "sweet spot" in a pack, I suspect that what John or Glen was referring to was the ability to read the actual apparent windspeed while riding in a pack. Functionally, you could find it just as well watching your wattage number, of course.

You don't have to use a flat, straight road. In fact, the right rolling venue can produce better results.