That ol' chestnut really needs to die. I'm riding my in the rain (sadly) about 7 months a year. One water-related hub failure in 8 years (on the origianal SL, before they started dipping the chips). Granted, I'm probably a little lucky, but everyone in the Pac NW who uses a tap is in the same boat as I, and I see a lot of people out there with Powertaps, racing and training on them.

As I posted before, no one goes out for a ride and comes back and posts "hey, my Powertap worked today". Because there are a disproportionate number of them out there (compared other PM's), you here more about it. All I can say is mine performs flawlessly in the rain, and I take no protective measures at all.

I'll second that. I got two PT's. An old style pro and a new style pro. No problems in the rain yet.

Excuse me? Since when? Apparently you haven't been reading all the threads about how people love their Ergomos. Mine has been great overall. I've considered getting an SRM because of the 1 leg/2 leg thing, but not unless they put in a good altimeter! This was the only issue I had with mine, the software was glitching in the first 2 minutes as the altimeter calibrated itself, and was screwing up the data. That's been fixed in later software, and the customization of the display is downright AWESOME. I've got power, avg power, cadence, norm power, speed, avg speed, time and distance all on one easy to read screen.

I've actually heard more bad things about PTs and water, even the new versions...

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I rent my ergomo screen out to touring rock bands in the off season for extra cash. :-)

But the point is how do you know the numbers you are seeing on the screen are the right numbers ... it might look nice and not break but so do cheapo speedo computers

Xav

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AeroCoach UK
http://www.aero-coach.co.uk

I know the numbers are correct because I do field aero tests and they are consistent within 1-2% from day to day and agree over a wide range of outputs with constant Crr and CdA from about 150W to 400W (which for racing is all that I am truly concerned about).

And with respect to the earlier 1-leg statements, the Ergomo does a pretty good job of accounting for leg discrepancies. I specifically tried two 20 mile TTs on 2 subsequent days and pedaled normally on the first day...264W at 23.1mph avg speed. The second day I tried to push harder on the right leg all the time, 211W at 21.5mph under very similar conditions, maybe slightly less wind. Given a known CdA and Crr I should have been at 225W at 21.5mph. That's not bad considering the huge discrepancy I was pushing at...probably 30% or better variation left to right leg. Taking the slight reduction in wind into account and I'd be surprised if the error was more than a few watts.

Realistically it's a simple thing to get a good estimate. Take the average angular velocity and power for the left downstroke, compare the angular velocity for the right leg downstroke and you have a pretty accurate "estimate" of power. I tried the "pushing down on the upstroke" unintentionally when I was tired, and it calculates it correctly. If I am beat down tired and not lifting correctly then my power output goes down, not up. When I look down and see the power at 210W and I think I am pushing a lot harder, I realize that I am not lifting on the upstroke. The second I start doing that my power output goes up 20-40W. My guess is they are measuring the twist on the upstroke of the left leg and subtracting that from the calculations, which is the correct way to do it.

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Whew. looks like I opened up a snake snest! Alot of great info and is really helping me decide which is better for me. Granted I won't be making a living being a triathlete and money saved is a good thing however, out on the racecourse money means nothing to me. I already have the new zipp disc which feels incredibly faster than my 404 and is very stable in wind so naturally I would try to race it all the time, so frankly another couple grand into my great expense called a bicycle is doable. I really, really, really want to qualify for kona so if having a piece of technology makes it easier to decipher my training, I'm there because lets face it-- training more doesn't neccessarily bring results.
The plethora of knowledge here is amazing.

thanx,
chris.

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Chris Bailey
Jupiter, Fla

Hello ,

and glad to join this forum !

Personnally , I use a powertape , a very good tool to appreciate my level of tireness .

Thanks for the info Tom!

Quote: "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 :-)"

fredly,

Interestingly enough...after installing the Polar unit and going on a ride, Tom A. suffered a massive cerebral hemmorage and died. May he RIP. Consequently, he will no longer be testing these three PMs simultaneously.

The COD from the coroner's report was extreme RFI (electro magnetic radiation).

Too much electronics are not good for the pocket book or one's health!

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Ben Cline


Better to aspire to Greatness and fail, than to not challenge one's self at all, and succeed.

Quote: "But the point is how do you know the numbers you are seeing on the screen are the right numbers"

Xavier,

You are measuring absolute power? Is it calibrated to the standard and what is the standard?

No, you are measuring relative power. Are you generating more or less power (watts) today vs yesterday?

The I generate 216 watts ave power and ride 23.65 mph with a PT over the same course John rides at 218 watts with a SRM at 24.87 mph. Why do I ride so much slower for only generating 2 watts less ave power? should never be the question. Mine is bigger than your's or your's is bigger than mine is not the point.

The point is measuring your performance (power output) from day to day and week to week over time to analyze one's training to get the most out of that training. That is relative power measurement.

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Ben Cline


Better to aspire to Greatness and fail, than to not challenge one's self at all, and succeed.

Yes, and I'm not convinced the Ergomo does that

Xav

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AeroCoach UK
http://www.aero-coach.co.uk

Recently bought my first modern computer a wahoo bolt .
It is suppose to read ant+ power info .
Will I have a reliable power measure if I now get a power tap
Hub in an a alloy wheel for $850.00 ?

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Gonna need 3 glow sticks.

Good god, you dredged up a 13 year old thread about the Ergomo?

(For the record, I did some analysis of the Ergomo after this thread and revised my opinion of it. It died a deserved death.)

That's a lot of money for a PT in an alloy rim

Maybe a decent price in 2007 - that’s around what I paid for my first Powertap wheel in 2011!! I’d go crank or pedal based. That being said, I was a two Powertap wheel guy (racing and training) for many years and it served me well. I made the conversion to crank based power meters in 2016 and have three Power2Max cranks that are super reliable.

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Blog: http://262toboylstonstreet.blogspot.com/
https://twitter.com/NateThomasTri
Coaching: https://bybtricoaching.com/ - accepting athletes for 2023

Wow, it was kind of a trip reading through this old thread!

Robert, do you happen to remember if this was one of the first times that the issues attendant to the "single leg and double it" measurement idea got raised in these/our circles?

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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/

Like you, i was a powertap guy, that is until they boned me.

Now i have 4 Power2Max's

Well, you guys were quoting my very first Ergomo analysis on my old webpage (I just noticed that this thread started a couple weeks before I joined ST) and we already knew that the Ergomo doubled the left side. It was the first power meter that did that. After I'd seen a couple more Ergomo files it became clearer that asymmetry wasn't constant but varied with both cadence and torque. I think I'd revised my opinion of the Ergomo several months before that thread started, so whoever cited that webpage didn't cite the page with my updated review.

On the one hand, the Ergomo head unit had the first built-in barometric altimeter. On the other, because it didn't use strain gauges you couldn't do a static torque check. That was where the "9-key" reference came from. Because "9-key" still matters, here's the original exchange, from February 2007 (i.e., several months before this thread originated:

A lot of love for P2M on ST. Ordered an NGeco yesterday as my first powermeter

Welcome to the snake pit.

Is R/L (both legs) power important to you? Do you need .5 watt accuracy? (it doesn't exist). Sounds like you don't want to change your set up and you want to use different wheels......Slap on a Dura Ace Stages PM and call it good......and save a truck load of money.

I think he got the answer about 12 years ago

Unless you are a committed speedplay user, I do not see why anyone would buy anything but Assioma Duos for $600 and use it on as many bikes as you want/got.

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Next races on the schedule: none at the moment

You massively underestimate the impact of assuming symmetry on accuracy, and more importantly, consistency. Either that, or you're trying to be deceptive with your 0.5W remark.
We're not talking about being 0.5W off, or even 5W off. We're talking a lot closer to 50W for many riders without resorting to any extreme outliers. If this were consistent it would be a problem for performance prediction but would work for most other purposes....but it's not.
How much is a Dura Ace Stages PM? I doubt you'll save much over something like Assioma Duo or P2M NGeco, which actually measures all of your output.
I don't think it's terribly important to know what each leg is doing independently, but if you want to measure power, you should measure total power of both legs or else why bother? - May as well just use HR or perceived exertion if accuracy and repeatability are irrelevant to you.
[Alex_korr]Unless you are a committed speedplay user, I do not see why anyone would buy anything but Assioma Duos for $600 and use it on as many bikes as you want/got.[/quote]
Yeah, I'd probably go with those, but I do use Speedplay and don't want to change. P2M NGeco isn't transferrable but aside from that it ticks all the boxes for value, simplicity to use and repeatability.

Thanks Robert!

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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/