ibike Power meter - Page 2

Good points. I never even see my PT when i ride in a fast group ride. I might glance down on occasion to see how many watts up a hill, but I look at wheels, not data!!

I also realized while talking to iBike that I look at Data not as a whole ride (averages), but I always pick and choose what I want to see and like you said-that datas not when I am coasting n the middle of the group. As long as its accurate when I am setting tempo or grinding up a hill or doing sprint work, its good.

Ray

Well, the reality is that there are technical benefits to training in a group. Riding a paceline, setting even paces, managing effort while in the draft, and for some - hanging on to the pack.

The majority of my monthly kilometers is solo and maybe 3-4 times out of two months I take part in a local group ride at high tempo to race pace. Our group rides are typically 4+ hours of riding.

One of the uses of the power meter is to gauge your overall effort of any ride. That time you spend in the draft is having an effect on your muscular usage. If you're in a rotating paceline of 5 guys and taking equal percentage of pulls, that means 80 percent of your ride will be underestimated, and the overall average power/normalized power output for the ride will read low. This likewise underestimates the TSS calculated for the ride.

All this completely depends on how anal retentive you are about the data you're getting from the powermeter. For me, every ride counts.

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Cycling Blog - Training with Power

Yes, I can see where you are coming from.

I think the point of iBike is that it provides a balance b/n price and functionality. If one has deep pockets, who wouldn't love a Ferrari, or SRAM PM? But for a large group out there who aren't anal retentive, who has a budget restriction, who would like to get the benefits of a PM based training scheme up and going, I'd say that iBike is an attractive product. Poo poo'ing iBike strictly on technical grounds is fair enough, but poo poo'ing iBike as a product is a poor response when no alternative solutions are provided for this group of riders.

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Morphed Bianchi Camaleonte IV 2006, Ridley Damocles 2006, Garmin, Mac

[QUOTE=ahaile]...I notice little effect in a pack but a definite effect in a small group, like 2-4 people...My watts numbers seem about 10-20% low in a small group. The theory I've seen floated around is that in a pack, the draft is large and fairly uniform, whereas in a small group, it's small and varied....

- It seems that 90% of the people criticizing the iBike on the net have never used one, whereas 90% of the people who have used it like it...QUOTE]

Interesting observation. I did a small group ride at lunch with 8 riders and lots of rotating and pulling through in really windy conditions on flat terrain. A friend on the ride uses a PT (and a polar)a nd it was interesting to get his AP/NP and compare it to mine for the 35 minute effort. His watts/kg were 3.3 AP and 3.99 NP, and mine were 3.26 AP, and 3.91 NP. Pretty darn close for a crappy power "estimator" IMO.

Your last observation had me in stitches because it rings true. What's interesting to me is even the coaching community doesn't make an issue of the iBike. I had a chance to sit down and review my data going back to last August with one of the leading experts on training with power and he didn't question the data or the device.

All I know is when the next gen of PMs comes to market and I toss the iBike on the scrap heap I'll feel that I got a helluva lot of value out of the thing.

gene r

I understand that there is a large group of folks that want the iBike for it's value as a lower priced training tool. If that portion of the community is glad to have it, I'm glad for them.

However, comparing power files from two separate riders - even on the same ride - is essentially useless based on someone's profile, ride position, efficiency in the group, etc... If they aren't side by side

I'm not saying that the iBike is useless, but it's important for people to know that it has definite limitations. I did my research before buying the PT SL back in October of last year, and while some of the "cons" have been fixed by firmware updates, some are not possible to fix because of the nature of the device and the way that it derives its power values.





I do often wonder how many people who have purchased the iBike have convinced themselves they like the device because that's the device they just spent $400 on.

Edited to add: As much as many convince themselves the PT is better in part because it costs more?

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Cycling Blog - Training with Power

LOL! I wonder that myself! Great observation! It seems that both "communities" seems to stand behind their choice for the most part and maybe that's the real story here.

gene r

I guess the question here is, is iBike good enough as a PM, good enough to function as a basis for power based training?

I don't yet have a PM but has been very interested in the various options out there. I see the potential advantage of iBike from angles of cost, weight, durability (no component wear) and portability. And if the PM reading is within 5-10% accurate, I'd think that's more than good enough for training in the scheme of things.

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Morphed Bianchi Camaleonte IV 2006, Ridley Damocles 2006, Garmin, Mac

I don't have an opinion on the iBike, but I do have an opinion on this as a test of PMs.

There are two purposes for on-bike PMs: first, as a recorder of what happens during a ride; and second, as a guide for structured training. Or, riding "with" a PM (which in my case usually happens on group rides during weekends) vs. riding "to" a PM (which is what I do during solo workouts on weekdays).

I haven't been paying close attention to these threads but my cursory impression is that there is plenty of evidence that the iBike does well in the "with" category. What's needed is more evidence that it does equally well in the "to" category. IOW, if you're going out to do a structured workout, will you be able to manage that workout equally well with either PM?

I don't get where this idea that measuring the current across a strain gauge is somehow more 'real' than measuring the current across an accelerometer, etc. The iBike has the potential to have all the data it needs to calculate a power number just as hub, chainring, BB and chain vibration systems do. Whether the number it gives you is of value or not, depends on your requirements. - TF

My experience has been that the iBike's works just fine for managing structured workouts, or should I say giving feedback during structured workouts. I'll use it during 2 x 20 LTs, at times glancing at "live power" or at times using the AP screen. For 5:00 vo2 intervals and short intense AC intervals I'll occasionally check live power. The device has a sub-trip feature so you see info, elapsed time, AP for that interval alone if you'd like.

The one complaint I have is that you can't see power and time on the same screen so you do have to toggle between the two, or what I do is put my Timex on my handlebars and use the stopwatch feature. I'd also love to have live TSS (like the Ergomo) but I've learned to calculate TSS (within reason) by using calories burned which the iBike does gives you.

I've only used a PT once and I would give it high marks as a device for managing a structured workout as well.

gene r

Yeah, my a priori guess would have been that the iBike could do well for 2x20 LT's. The real question is, "what kinds of structured workouts, if any, are more reliably managed with one PM than another?" For example, we know single-leg drills aren't well-managed with the Ergomo -- but if you don't do single-leg drills, who cares? I suspect (but don't know) that the iBike wouldn't do well in sprint drills -- but if you don't do sprint drills, who cares?

Each PM has strengths and weaknesses for particular purposes. I think it makes sense to try to identify what those are.

The thing I cannot get out of my head is racing on a 1200g wheelset AND having a power meter. At $500 or so (assuming two extra mounts on different bikes) it makes it hard to stomach the same potential situation with an ergomo or SRM.

Terry:

A non-negligible part of my real job (the one that pays me insultingly mediocre amounts) is explaining to people why not all mathematically or logically equivalent ways to calculate something give estimates of equivalent quality. To paraphrase Tolstoy, good estimates are all alike; every poor estimate is poor in its own way.

Compare apples to apples, and I'm not sure the argument that the iBike is a less expensive power meter is all that valid. By the time you pay for the iBike with cadence, a decent heart rate monitor and good software, you're probably going to be in the same price range as a new or slightly used PT SL and wheel on eBay. You'll also be paying about as much as the list price on the new Polar CS600 system. Once you have the kluged together iBike system, you'll still be without the ability to use it on a trainer, still have problems getting accurate readings in a pack or if you change position on the bike, and downloading and comparing HR to power data will be a problem.

The purpose of a power meter is to record and display useful data. Much of the most useful power data is developed and/or needed during competition. iBike can not record or display that data accurately or consistently and that's a big negative.

If 25% of your training is done indoors, iBike is useless 25% of the time. Consider the loss of useful data when riding in a pack might account for 25% more time when the iBike is useless, and the bottom line is that it's useless about half the time. Even if it works well the other 50% of the time, it's still no big bang for the buck.

Estimating three of the terms of the equation of motion of a bicycle isn't close enough for many of us and ultimately, it's the torque you are putting into the drivetrain that moves the bike forward (on level ground) and not just three of the factors resisting your forward motion. (http://freewebs.com/velodynamics/guide3.pdf and go to page 28)