iBike vs Power Tap SL

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miket5200
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iBike vs Power Tap SL

Post by miket5200 »

....Okay. Here's my story. I've had and used a Power Tap SL for over 2 years and it's been very reliable. The iBike intrigued me so I bought the new wireless model. I did about 20 CD's and 3 four mile rides. Before each ride I do the tilt, wind offset etc. AND I still can't get any data that is close to the Power Tap. Sometimes it may be close AFTER the data is analyzed.... but usually it's not close especially the max watts. See the table that I built below.

So my questions are: 1) How do you know that your iBike is accurate without another PM to compare it to? If I didn't have the PT on at the same time I would think that I'm much stronger than I am.... the Max Watts are WAY off. 2) If I have to analyze the data AFTER the ride to get it more (?) accurate what good will it do me when I riding/training? 3)
The bottom line is I don't see how this can be a viable answer to PT or SRM power meters. Any one care to explain this?

As a side note it seems to be a 'little' more accurate when climbing as you can see from the table. Also, the "before" is data before it's analyzed and "after" is after it's analyzed.

Cheers.
Mike


% Change from Power Tap % Change from Power Tap
Date Distance Time Climbing Avg Watts Max Watts

PT SL 6-Jan 30.2 1:43:00
iBike (before) 1150 24 130
iBike (after) 1147 3 17

PT SL 10-Jan 31.4 1:46:00
iBike (before) 1098 17 14
iBike (after) 1097 8 10

PT SL 15-Jan 38.4 2:18:00
iBike (before) 2183 33 187
iBike (after) 2325 11 38

PT SL 19-Jan 82.6 4:21:00
iBike (before) 3111 15 96
iBike (after) 3106 12 6

PT SL 21-Jan 44.0 3:40:00
iBike (before) 6796 4 48
iBike (after) 6796 3 - 26

PT SL 22-Jan 57.7 4:45:00
iBike (before) 8809 3 52
iBike (after) 8807 1 12

PT SL 23-Jan 20.8 1:30:00
iBike (before) 2315 27 55
iBike (after) 2316 26 54

PT SL 24-Jan 43.3 3:59:00
iBike (before) 8437 -1 -5
iBike (after) 8445 4 -26

PT SL 25-Jan 19.6 1:36:00
iBike (before) 3131 -3 32
iBike (after) 3131 -1 -2

PT SL 27-Jan 34.4 2:02:00
iBike (before) 2506 0 71
iBike (after) 2502 3 13
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markmergler
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Re: iBike vs Power Tap SL

Post by markmergler »

Mike

I cant make sense of your data - have you looked at how it is formatted in your post?

Maybe you could put it in a spreadsheet and attach it to the post?

Mark
michaeltop
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Re: iBike vs Power Tap SL

Post by michaeltop »

What sort of interval are you looking at for peak power? When you yank on the bars for a sprint you will be increasing tilt and thus max power reading.

Now if your seated 1minute sprint power of 1400 watts at 150 rpm is off, then there is cause for concern. Hit 800 watts for 3 minutes and you can win a lot of entered races.

As a training tip , if you use the interval function and AVG power readings while doing a ride, it is very hard to meet the training levels for the workout. That is the advantage of the ibike. Those numbers track very close to powertap numbers. I find the faster i go the better the correlation with my powertap. Better to measure peak power by jersey's not theory!

thats my 2 cents.
miket5200
Posts: 8
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Re: iBike vs Power Tap SL

Post by miket5200 »

Mark.... and all. Sorry about the formating. It looked good when I typed it in. Anyway, I tried to attach the spreadsheet that I made but it wouldn't let me upload a file with an .xls extension. So I copied it to word and it wouldn't let me upload a file with a .doc extension. I also tried saving to all sorts of extensions but none would work. Any suggestions?
Cheers,
Mike
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Re: iBike vs Power Tap SL

Post by michaeltop »

Best way to upload some of the data is just copy and paste.

Peak 20min (228 watts):
Duration: 20:00
Work: 274 kJ
TSS: 29.5 (intensity factor 0.942)
Norm Power: 245
VI: 1.07
Distance: 10.013 km
Elevation Gain: 46 m
Elevation Loss: 50 m
Grade: -0.0 % (-4 m)
Min Max Avg
Power: 0 511 228 watts
Speed: 0 34 30.1 kph
Pace 1:46 0:00 1:60 min/km
Altitude: 21 36 26 m

Peak 20min (226 watts):
Duration: 20:05
Work: 272 kJ
TSS: 30 (intensity factor 0.949)
Norm Power: 237
VI: 1.05
Distance: 10.174 km
Min Max Avg
Power: 0 487 226 watts
Cadence: 29 109 71 rpm
Speed: 5.1 34.5 30.5 kph
Pace 1:44 11:46 1:58 min/km
Hub Torque: 0 21.4 9.0 lb-in
Crank Torque: 0 74.6 31.0 N-m

This is an example from a ibike vs powertap ride. Last year I used the powertap/ibike setup for about 2 months to satisfy myself that TSS , intensity and avg power values are close in measurement. Thanks to the profile function in the software, i just upload the correct bike, do a tilt and offset setup, then go. Yes the ibike can give some funny values, but day to day numbers are quite reliable.
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Re: iBike vs Power Tap SL

Post by Site_Admin »

miket5200 wrote:Mark.... and all. Sorry about the formating. It looked good when I typed it in. Anyway, I tried to attach the spreadsheet that I made but it wouldn't let me upload a file with an .xls extension. So I copied it to word and it wouldn't let me upload a file with a .doc extension. I also tried saving to all sorts of extensions but none would work. Any suggestions?
Cheers,
Mike
Send me a PT file and an iBike file, please. You have my information.
miket5200
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Re: iBike vs Power Tap SL... Data File Attached

Post by miket5200 »

... Attached is a .pdf file. Thanks to: gray8101 for explaining how to do it. Now you'll be allow you to see/understand the data better.
Cheers,
Mike
Attachments
PT vs iBike Data.pdf
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Re: iBike vs Power Tap SL

Post by Site_Admin »

Mike -
I forgot to ask you to send me your ibp profile. Please forward that when you can.
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Re: iBike vs Power Tap SL

Post by Velocomp »

To paraphrase Ronald Reagan: here we go again!

Ever wonder why you NEVER see direct, moment-by-moment comparisons of power meter files? The answer is simple: it is extremely difficult to do! Differences in ride file sampling intervals, differences in electronics, variances in unit-to-unit manufacturing quality, even differences of when the ride file starts from zero, make it next to impossible to do what would seem to be very simple: line up two ride files side-by-side and see how they compare.

Instead, what everyone does is use summary statistics, such as found in WKO+, for comparisons.

We like summary stats too, but how about DIRECT comparisons, moment-by-moment?

We decided it was time to really get to the essence of how power meters compare: not just the iBike with others, but even other power meters against each other. And we decided to let the data speak for itself, moment-by-moment.

It's now possible to do this with new software we've developed. We can compare the iBike against any other PM. (We can compare an SRM against a PT too, or any other two or more PMs, for that matter). We accomplish this by aligning the speed data from different ride files (which should be identical for any good cycle computer) and use the speed alignment to line up the other data (power, cadence, HR).

No more hiding or generalities allowed!

Mike was kind enough to supply 5 iBike ride files, as well as the corresponding PT files. I'm told that his setup is a wireless handlebar iBike, no VRK, on a standard size bar.

We've taken a look at the five ride files Mike supplied using our new software we can see some very interesting things:

1) Multiple coast down and 4 mile calibrations were done.

2) We saw 4-5 drop-outs on each ride. The iBike 2 software repaired them properly.

1) For a couple of rides (Jan 10 and 19) the tilt calibration appears to have iBike shifted. This can be seen clearly in the comparisons. I'm told that the double sticky tape wasn't used in the iBike handlebar setup so this may be the reason the tilt shifted.

3) There were also rides where the iBike tilt did not shift (Jan 6, Jan 22 and Jan 27). On those rides the iBike was within 1W, 1W and 5 watts of the PT, respectively. Detailed comparison data for the Jan 22 ride are attached. This is a ride with hills and flats...and please remember, this is Mike's data, not ours!

4) For rides where the tilt calibration shifted (Jan 10 and 19), the iBike was different by 10 and 15W respectively. This is a difference of about 5%-7%.

5) No VRK is used in this setup. The VRK eliminates most drop-outs, improves on-the-bike watts, and improves the iBike's accuracy even more. Based on on our testing, the iBike works even better when the VRK is used.

We've blown up the Jan 22, 57 mile ride into 5 attachments. You can judge for yourself how close these two PMs are. To smooth out cadence noise we've used 30 second filtering.

Are we always identical? No, but with good reason (more about this in the future). And based on lots of data we can unequivocally state this, too: NO TWO PM BRANDS GIVE IDENTICAL RESULTS, EITHER!

You'll be seeing a lot more comparative data from us. Remember: we already have an iBike, an SRM, a PT, and Ergomo on our bike, and we're about to add another PM, too. We've got a LOT of data...
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John Hamann
michaeltop
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Re: iBike vs Power Tap SL

Post by michaeltop »

it's now possible to do this with new software we've developed.
would be nice if you post that software on the ibike site for download by registered owners
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Re: iBike vs Power Tap SL

Post by Site_Admin »

It's a WIP.

And as Dean Wormer said in "Animal House" - "You'll get your chance, tough guy!" :x

Seriously - this is big. Really big. please hang on. My own nails have been bit to the nub on this.
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leonsrocketcar
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Re: iBike vs Power Tap SL

Post by leonsrocketcar »

john,

Thanks for sharing this post prior to a "major annoucement" to the world. I catch alot of sh :o t from the "other" PM guys out there and I am starting to cave under peer pressure, but using some science and user data really adds weight that this is a product I should continue with and not jump on another platform just cuz my boys are doing the PT/SRM pinky touch. But I still have queries which there is a thread somewhere on this site about drafting and the iBike. I believe :geek: Travis :ugeek: said this study is on the books too.

Kevin
Kevin
Sugar Cycles
http://www.SugarCycles.com
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Re: iBike vs Power Tap SL

Post by Site_Admin »

See you in two weeks down at SW Cyclery, and we can do more than eyeball.
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leonsrocketcar
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Re: iBike vs Power Tap SL

Post by leonsrocketcar »

Whareagle wrote:See you in two weeks down at SW Cyclery, and we can do more than eyeball.
Thanks Richard, we'll make contact offline on details of the time you are at SWC.

I do remember in the old forum or somewhere seeing a post where you had every known PM attached to your bike in some form or fashion, sorta looked like a gaming control center on your handlebars :lol:
Kevin
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Velocomp
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Re: iBike vs Power Tap SL

Post by Velocomp »

Yep! And this is an old photo; we've now added an additional 2 iBikes to Richard's bike. We're pleased that the next one we will add won't take up any more real estate...
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John Hamann
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Re: iBike vs Power Tap SL

Post by Site_Admin »

Today really hurt. We went out to Longview for the "Freeze Your Fanny" rally, and after about 15 miles or more we were pared down to about 4 riders - LaSport, UT dude, Mighty Whitey, and me. The terrain in Longview is actually pretty challenging, and while it definitely warmed up over the course of the day, it started off a little chilly. The winds were present as well.

Due to some solid indoor training this winter, albeit not as much overall volume as I'd like, I was gapping the other three guys on the 1-3 minute hills, sometimes up to about 20 seconds or so. But the course was poorly marked, and the biker dudes who were supposed to escort us ran off to the nearest honky tonk to go chase Jay Leno's Dreams, and so we always ended up regrouping. It was at about mile 20 that I learned that Mighty Whitey wasn't taking his share of pulls. He complained of dead legs. I didn't let it bother me until we dropped College Boy and then it really started to irritate me.

Those of you not familiar with the rally scene in N. Texas, these rallies are de facto races or training races, done for God, Gold, and Glory. People scheme for years on winning "The Big One", either in Mesquite or Meunster or even the 2-day MS150 between Dallas and Ft. Worth. But to not take a pull is a cardinal sin - even if it involves glass pedaling. You give the other guys a break.

So, being the lightweight draft horse that I am, I pulled with LaSport, and Mighty Whitey sat on the back eating hamburgers. Then, around mile 40....

Freakin MIGHTY WHITEY comes around, launches a brutal attack on me AFTER I've climbed a 2-minute hill of maybe 4% and 1/2 a mile, and LaSport goes with him. We'd been in an open area, and LaSport's TriSpokes kept stalling in the crosswind, so he was kind of all over the place, and I couldn't stay with them - he caught me at a moment when I was shaking my head trying to think about what I was going to tell LaSport next time he did a fat-man's wobble. So while I'm recovering, they're off to the finish line.

However, LaSport truly WAS a sport, and he actually came back and we worked together to recapture Mighty - although at about Mile 48, I'd burned my matches, and launched LaSport back to his comrade, and they finished about 3 minutes or more up on me. I literally almost got sick trying to hold pace, and the crawl back in is always humiliating - ask Floyd.

Why is this tale in thi thread? Idunno. I guess it was just to say that you can finish in the Top 3 of a 'race' with all that Stuff on your handlebars. We'll run the numbers, do the analysis, and fire off comparisons, but nothing works better than heart, soul, and preparation for battle.

Adios, hombres and hombrettes. Talk with you on Monday.
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Isaias
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Re: iBike vs Power Tap SL

Post by Isaias »

^^^^^^
Thanks for the great story, Rich! Is UT dude the same one that hangs on BikeForums.net?

This "dude"?
Image

Makes my little adventure in the mountains, Saturday, seem quite literally "pedestrian":

Image

http://www.flickr.com/photos/wabeck/set ... 839729492/
Paul
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Re: iBike vs Power Tap SL

Post by Paul »

Coach,

You've got at least $6-7k worth of PM equitpment in that cockpit! People must think you are a power junkie :shock: !
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Re: iBike vs Power Tap SL

Post by Site_Admin »

Hey - go read "The Right Stuff" and you'll understand.
Gregory Au
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iBike vs SRM professional

Post by Gregory Au »

Unfortunately I have to say I have the same experience with miket5200.

I have an SRM V professional running side by side with my iBike (latest version, multiple coastdowns, profiled etc etc) and even after iBike 2 software post processing I do not get values from my iBike that consistently match the SRM.

Sometimes the values can be similar, however, often they may differ by 10%. Cyclingpeaks WKO+ TSS values are also similarly off.

I am a bit upset about this, I really have put a lot of time trying to set up the iBike but I just don't seem to get similar data. I think the iBike is more accurate on uphills but less so on the flat.
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Re: iBike vs Power Tap SL

Post by Site_Admin »

Greg, you need to send me files of both the iBike and the SRM (preferably same ride), and send me your Profile (you can export that to your desktop and include in the e-mail). We'll have a look and maybe publish the results of what we find.
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Re: iBike vs Power Tap SL

Post by Gregory Au »

OK I did another ride today this AM (large bunch ride, lots of drafting, fast turns out front) but used different wheels Ksyrium SLs rather than my 45mm deep carbon wheels. I didn't change my profile, which was gathered from coast downs and 4 mile ride with the carbon wheels. I have not changed the setup of the bike other than the wheels, the unit has not been recalibrated nor has the mount been adjusted.

I am actually very surprised that the result is actually very similar

iBike
Entire workout (159 watts):
Duration: 1:52:05
Work: 1067 kJ
TSS: 157.3 (intensity factor 0.918)
Norm Power: 248
VI: 1.56
Distance: 59.344 km
Elevation Gain: 755 m
Elevation Loss: 771 m
Grade: 0.0 % (0 m)
Min Max Avg
Power: 0 828 159 watts
Speed: 0 62.8 31.8 kph
Pace 0:57 0:00 1:53 min/km
Altitude: -55 75 -13 m



SRM
Entire workout (164 watts):
Duration: 1:51:45 (2:19:59)
Work: 1100 kJ
TSS: 154.6 (intensity factor 0.911)
Norm Power: 246
VI: 1.5
Distance: 58.511 km
Min Max Avg
Power: 0 918 164 watts
Heart rate: 0 173 133 bpm
Cadence: 30 182 84 rpm
Speed: 0 62.8 31.4 kph
Pace 0:57 0:00 1:55 min/km
Crank Torque: 0 97.7 18.8 N-m

Now, my question is does iBike accuracy vary when when travelling at high speed if one uses Aero vs Non-Aero wheels?

I will be doing further riding with both powermeters on the standard Ksyriums.

Greg
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racerfern
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Re: iBike vs Power Tap SL

Post by racerfern »

Gregory Au wrote:Now, my question is does iBike accuracy vary when when travelling at high speed if one uses Aero vs Non-Aero wheels?

I will be doing further riding with both powermeters on the standard Ksyriums.
I'm by no means a professional at this. However, I cannot imagine using the same profile for either set of wheels. You NEED to have a separate profile for wheels that are so drastically different. The Kysrium's are excellent climbing wheels that are not very fast in aero situations. They also react adversly to wind from the side (obviously). If you could do two sets of coastdowns in identical conditions you should see quite a difference in the two profiles.
Fernando
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