"Really? You mind pointing me to one?"

Google it, or search the wattage archive. I need to go teach a Cyclocross class!


" I just referenced one pretty detailed comparison that showed no discrepancy at all."

1 rider for 1 ride is a detailed comparison? You have a significantly lower confidence threshold than I do.


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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

You said: "The evidence from this limited sample of data (i.e., 1 ride from 1 rider)" 'nuff said.


You also said: "Take a look, there's plenty of it out there, and it doesn't take a "severe... discrepancy" to skew the data, at least from the n=1 that I had data for."

Sooo, your n=1 is somehow more valid than the other n=1? LOL. Please.

"There are credible reports (other than mine) of this being problematic for certain riders."

Again, please post a link so we can assess. I've never read one.

"Why buy a unit that may or may not work, based on a problematic (even if merely theoretically, for you, maybe, you will probably never know...) method of data collection?"

Because the only theoretical argument here is yours. All valid data I've seen points to the Ergomo being as accurate and repeatable as any other measurement device. All this fear-mongering about how it only measures one leg and doubles it has never been substantiated with any sort of data.

As long as the rules you're racing under allow wheel covers (is this for triathlons or TTs?), a PT/404 with a cover will be as fast, and possibly faster, than most "true" discs (with the exception of the new "sub 9" disc, that is.)

Also, just a nit to pick, but IMHO if it's windy out, I'm going to reduce the surface area of my front rim to minimal before taking my rear disc off. A rear disc actually helps maintain stability in windier conditions by helping keep the "center of pressure" more rearward. Just yesterday I took my TT bike out for the first time this year without the cover on my PT wheel. Even in light breezes it felt a lot less stable. Just my 2 pesos.

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http://bikeblather.blogspot.com/

Interestingly enough...at the present time I have both an Ergomo Pro AND a PT Pro on my TT bike and I'm running them concurrently ;-)

I'm actually going to be mounting my Polar power unit (wired version) on there as well for a short period of time. It's too early in the evaluation process to make any comments one way or the other about the Ergomo.

Expect to see a full write-up of my findings here on ST in the future :-)

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http://bikeblather.blogspot.com/

"Sooo, your n=1 is somehow more valid than the other n=1? LOL. Please."

Yup. One rider, 45 rides. Not even in the same ballpark as 1 rider, 1 ride. N still = 1.

"Again, please post a link so we can assess. I've never read one."

Sorry, not interested enough to do the legwork for you.


"Because the only theoretical argument here is yours. All valid data I've seen points to the Ergomo being as accurate and repeatable as any other measurement device. All this fear-mongering about how it only measures one leg and doubles it has never been substantiated with any sort of data. "

Cool. Enjoy your Power meter. Frankly, I think it's great that people seem to like their Ergomos. As long as I don't have to coach them or crunch their numbers, whatever makes folks happy is fine by me. If that sounds like "fear-mongering" to you, well, let's just say that you live in a significantly less scary world than I do...

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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

I have been through this the hard way. If you want to save money in the long run and have a reliable peice of equipment go with the srm from the start. If the price is an issue then the power tap.

If you would like to pick my brain give me a call. It will be quick, not much to pick :o

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Richard Nixon, Fit2Tri Multisport Inc.
Fit2Tri,
rich@fit2tri.com
Discount code, slowtwithch

"Google it, or search the wattage archive."

OK, for laughs (slow afternoon at work) I Googled "ergomo leg discrepancy" and found this:

http://www.cruciblefitness.com/...ic.asp?TOPIC_ID=3491

Among the notable excerpts are:

"I have a SRM Pro on one bike and a PT on the other. Based on a couple recent rides, it seems that at least one of them is off by 20+ watts. I always set the zero for each meter before my ride, so I'm afraid I need to do something a little more involved to get this straightened out."

and another user's account:

"First, my sympathies. I have both an SRM pro and the new Ergomo installed on my TT bike (it's work related). Most of the time, the two are within a few watts. But, every once in a while there's a 20-30 watt difference."

and yet another quote from the same poster:

"I actually have two SRM V computers and they are always 40 watts different (which is really odd considering that I'm actually using the same sensor). Go figure."


So, it appears that the PT and SRM don't agree with each other, two SRM's reading off the same sensor can't agree with each other, and the Ergomo and SRM can't agree with each other. Yet, somehow this can all be traced to the fact that the Ergomo only reads one leg ;-)

You're an Ergomo dealer? Way to promote your product!

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Steve Perkins

"Interestingly enough...at the present time I have both an Ergomo Pro AND a PT Pro on my TT bike and I'm running them concurrently"


Cool. I will be interested (well, slightly :0) in the results. My n=1 was enough to convince me that the product has issues; even if it's only a concern for a certain (small?) percentage of riders, if you can't tell that you are one of those people...


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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

"You're an Ergomo dealer? Way to promote your product! "

Hey man, I'm honest! I'm also a PC dealer, and it's pretty clear how I feel about those.

If someone walks into the store and asks for a powermeter, I can sell them an Ergomo if they want one - but I would much rather sell them a PT or an SRM. If a customer asks, they will get the same summation I gave here.


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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

"So, it appears that the PT and SRM don't agree with each other, two SRM's reading off the same sensor can't agree with each other, and the Ergomo and SRM can't agree with each other. Yet, somehow this can all be traced to the fact that the Ergomo only reads one leg ;-) "


I'm going to give you the benefit of the doubt, and assume that the smiley indicates that you know just how ridiculous this summation is...



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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

Hey, I'm all for honesty, but why sell the thing if you think it's that bad? I mean, a few more dealers like you, and Ergomo may as well shut its doors.

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Steve Perkins

So, you're a dealer but you only have feedback from one customer, and that was enough for you to reach your conclusion that the product has issues and you won't recommend it. Please reference my sig line, which ironically quotes you.

Hey Tom -

Just as a sidenote, and pertaining to your "study"...

In my informal N=1, we seemed to see indications that wattage assymetry was nonlinear through the range of rider output, and increasingly so at certain levels of fatigue...


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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

" So, you're a dealer but you only have feedback from one customer, and that was enough for you to reach your conclusion that the product has issues and you won't recommend it. Please reference my sig line, which ironically quotes you. "


Too funny.

I have (numerous) data sets from one rider, and blown BBs from others (which was the other part of my initial response, remember?)

Here's a question for you - you seem a strong advocate for this product; do you have any data to support your assertions as to it's accuracy and precision? Have you made any attempt to analyze your data sets against a known standard?

As to "irony," well, in order to BS, I would need to, well, BS, and I'm not. I have data, I have bb's, and I have the surfeit of used Ergomos on the classifieds to support my assertions. Other than sophism, what, exactly, are you bringing to this discussion?


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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

Right now I'm just riding with them together outside and basically allowing things to "settle in". The offset actually has been very stable from installation through the first few rides. I may want to slightly "tweak" the BB orientation though since I'm not exactly at the 9 O'clock point (it's ~10-15 deg below horizontal right now). My plan is to eventually include a session on a trainer stepping through the gears at a constant wheel speed (i.e. constant power) and then also stepping the power level at a constant cadence to check linearity between them.

Although it's WAY too early in the eval process to say anything of note, I think I may be observing variation between the 2 meters based on how much I'm "mashing" or "spinning"...which, since the Ergomo measures BB twist, would be a logical effect. In other words, if you're doing something to reduce BB twist (such as unweighting your "off" leg) then the power reading will be too low. Conversely, if you aren't unweighting at all, or even actively pushing down on the upstroke, the BB twist will be increased and the meter would read high, especially since that case would actually work against your power output to the rear wheel. The question is: Is it measurable? This could also be an explanation for the fatigue related differences you say you observed, right?

One of the reasons I'm going to be mounting the Polar on the rig as well (besides having another "check" on the system...I've found my Polar and the PT to track VERY well with each other) is that I'd have access to the "pedaling index" values from the Polar. I don't know if it will tell me much since PI doesn't actually "separate" the 2 legs, but it may be something interesting to look at...then again, it might not ;-)

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http://bikeblather.blogspot.com/

SRM is the gold standard. If you've got the money, this is the ONLY way to go. I run an SRM on my road bike and it is flawless. Easy to work and upload results. Day in, day out, this meter cranks the numbers out with no issues. (2005 Cannondale Six13 SRM)

PT is a good choice if you're on a budget, but it's defintely not a substitute for an SRM. I run a PT 2.4 on my tri bike (Bontrager Aeolus 6.5 SRM wheel). The PT works okay, but mine has been back to factory once this year and now the bike computer is having an issue. Also, the USB cradle for PT can be difficult. Nine times out of ten it detects the computer with no issue, but the tenth time I have to "re-seat" the PT to get it to recognize. Also, and I know this is getting kind of picky, it takes a great amount of force to remove the PT from the docking cradle (I'm afraid I'm going to break something). Great setup for the price.

Both meters seem equal as far as the wattage numbers they display (my PT reads a few watts lower than my SRM) and for my purposes I'm happy with both meters. Both Saris and SRM have great customer service.

I wish my SRM were on by Tri bike (Cervelo) so I could run a disk. (My SRM is on a "proprietary" Cannondale crank).

I've owned an Ergomo Pro and in my case, the unit was basically junk! I got rid of it on eBay, along with Ergomo crank and replaced it with the PT 2.4 above. The problem was the numerous issues I had keeping it calibrated. I can count on my fingers the number of rides I got ANY useful data from the Ergomo. The bike computer is a "brick" and because it's so large, difficult to mount to aerobars. Be sure you buy an Ergomo from a local dealer that can support you as customer service leaves something to be desired. I've heard that the Ergomo has improved over the past view months due to firmware upgrades, but I'm not willing to try one again. Oh yea... If you get an Ergomo, don't let the battery go dead... bad things happen.

Oh yeah...you stated you want to run Q-rings. A word of caution about using those with an SRM. Since the SRM assumes a constant angular velocity, you may experience inaccurate power readings (i.e. too high) when running Q-rings in conjunction with an SRM. This is because the non-round shape of the rings causes variations in the crank angular velocity (at a constant wheel speed) and the "on" portions of the stroke are weighted too heavily in the power calculation.

Jens himself observed this when running an SRM, PT, and Q-rings all together. The SRM displayed higher power relative to the PT with the Q-rings than with the round rings. Gregclimbs is putting together a test setup to get to the bottom of this once and for all, right Greg?

Just thought I'd warn you...;-)

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http://bikeblather.blogspot.com/

http://www.humankinetics.com/...rticle.cfm?aid=10426

IJSPP, 2(3), September 2007, Copyright © 2007

Validity and Reproducibility of the Ergomo®Pro Power Meter Compared With the SRM and Powertap Power Meters

Sébastien Duc ; Vincent Villerius; William Bertucci ; Frédéric GrappeFull Article Table of Contents for Vol. 2, Iss. 3

Abstract
Purpose: The Ergomo¨Pro (EP) is a power meter that measures power output (PO) during outdoor and indoor cycling via 2 optoelectronic sensors located in the bottom bracket axis. The aim of this study was to determine the validity and the reproducibility of the EP compared with the SRM crank set and Powertap hub (PT).

Method: The validity of the EP was tested in the laboratory during 8 submaximal incremental tests (PO: 100 to 400 W), eight 30-min submaximal constant-power tests (PO = 180 W), and 8 sprint tests (PO > 750 W) and in the field during 8 training sessions (time: 181 ± 73 min; PO: ~140 to 150 W). The reproducibility was assessed by calculating the coefficient of PO variation (CV) during the submaximal incremental and constant tests.

Results: The EP provided a significantly higher PO than the SRM and PT during the submaximal incremental test: The mean PO differences were +6.3% ± 2.5% and +11.1% ± 2.1%, respectively. The difference was greater during field training sessions (+12.0% ± 5.7% and +16.5% ± 5.9%) but lower during sprint tests (+1.6% ± 2.5% and +3.2% ± 2.7%). The reproducibility of the EP is lower than those of the SRM and PT (CV = 4.1% ± 1.8%, 1.9% ± 0.4%, and 2.1% ± 0.8%, respectively).

Conclusions: The EP power meter appears less valid and reliable than the SRM and PT systems.

Why would a wheel cover be faster than a disc? I was considering a disc or waiting on a Blackwell 200mm wheel with a PT hub but would prefer a wheel cover for under $200 for my PT/404's as opposed to the alternative $$$$$$$$$$$$. It wouldn't look as sexy but my checkbook would be digging it.

I have two Ergomo pros that I've been using for about a year and even though I've had problems with them, it has been because of not taking care of them properly.

I do a lot of my training during the hard winter months and when it comes to powermeters working correctly in bad conditions, Ergomo takes the cake.

Check this out - http://www.peakscoachinggroup.com/LaRuta.html

I'll start off apologizing for a couple of things- first off, I don't want to make this a personal thread, and my last post was a bit of a personal attack so I apologize. Secondly, it's not my intent to advocate for the Ergomo so much as to challenge the conclusions you've reached based on what appears to me to be insufficient data and data that's contradictory to so much other data and anecdotes that's out there and that I've provided links to. After all, your n=1 may have 45 rides, but it's still one rider on one PM. When you suspected the data was wrong, what steps did you take to address this? Did you swap the BB for a different one? Did you try to re-install and compare data? I just find it odd that someone that comes across as skeptical as you would reach such a broad conclusion based on this limited set of data.

As far as what I bring to the table, I've got over 100 rides on two different Ergomos with zero mechanical problems, and with excellent repeatability on the same loops in similar conditions. Have I attempted to analyze this against a "known standard"? No, and I wouldn't even know what that known standard is to compare to. After all, by at least one account the accepted "gold standard" SRM showed a 40W variation from one unit to another reading the same sensor. Is this what I should compare to?

Question on the blown BB's - were these Ergomo Pro's or the older Ergomo Sports? I heard numerous reports of bad Sport BB's but I have not heard of any bad Pro BB's. The new design supposedly corrected that problem. I'd be curious to hear what the typical failure mode was. Was it the electronics or the seals?

As far as the classifieds being any indication of anything, you're joking right? I sold mine in the classifieds here a while back because I was taking a break from training. Did you personally speak to every seller to ascertain their reason for selling? I also see SRM's for sale. What should we make of that? (hint- nothing).

Well...a properly mounted wheel cover on a low profile rim gives up nothing to a "true" disc aerodynamically (a disc is a disc is a disc) . If you put a cover on a 404 wheel you're able to take advantage of the Zipp "bulge" which helps to reattach flow under certain conditions. If you put one on an 808 style wheel, you'll have the closest thing possible to the new "sub 9" disc and it's "negative drag" (i.e. propulsive force) under certain conditions.

BTW, a wheel cover custom cut to your 404 rear is going to be WELL under $200. More like $95 for one trimmed to a 404 and with the center hole opened up for a PT. Look here:

http://www.wheelbuilder.com/...pid=185&offset=0

Like I said before, if the rules you're racing under allow a cover, it's pretty tough to beat a cover on a 404 or 808 wheel...especially on a "bang for the buck" basis!

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http://bikeblather.blogspot.com/

That sounds like a calibration issue for the SRMs. Fortunately, that's something that the user can check with a static cal and correct. In fact, I know many people who recommend doing a static cal on ALL SRMs, even brand new ones fresh from the factory, just to ensure good numbers.

Unfortunately for the Ergomo, no user calibration or even a calibration check is possible. For this type of sensor and construction, you don't know if you're getting correct numbers without comparing it to another PM. Not everyone has that ability. You may not care now if the numbers you're seeing are correct and only care that they are consistent. However, without a comparison, you won't even know if they're consistant. But, in the future, if you get another type of power meter, you won't be able to make any meaningful comparisons.

This is a tough issue for the Ergomo...no two ways about it.

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http://bikeblather.blogspot.com/

If I ever got another power meter, I'd do an FTP test on that and compare that data to my current data set. Seriously, is it really a consideration to be able to compare data between different power meters? Even if there existed a "golden" PT and a "golden" Ergomo and a "golden" SRM which all read the "true" wattage, they'd likely show different data- at least the SRM and Ergomo would be different from the PT due to drivetrain losses. What's a reasonable amount of drivetrain loss? Did I clean and lube my chain the same on every ride? What was the condition of the cassette on a given training day? There are just too many variables to think you could take data from one PM and compare it to data from another PM without some sort of bridge.