Ergomo Validity shot down....

Absolutely not. No. The SRM is not accepted to be 'absolutely precise' by any right thinking person. It is accepted that it has a low error (particularly in the science version used in the study). This is not 'just because its on the market for 20 years', but rather because it has been validated over and over in a number of scientific studies. Powertap has also been subject to some of these studies and passed well. For Powertap there has been a question identified in the literature of small variations in very high wattage situations depending on gear selection/cross-chaining. It's very minor though, not at all like the wild fluctuations the Ergomo had in the study.

Ergomo falls down at the first hurdle.

 

At their booth they had a Cyclus ergometer with a Ergomo mounted and you could compare the values. In all situations the values were comparable. As the head of service pointed out, PT and to a lesser degree SRM are fool proof regarding installation, while Ergomo is not. So in a "real" test, one should compare a Ergomo installed by Ergomo with a SRM and then one could really draw conclusions. Until then, this study seems to be guesswork to me. Of course, they got these results, that I do not doubt. What I do doubt is the basis this values originate from (i.e. installation).

BTW, Ergomo mentioned that different torque when a SRM crank is mounted on the BB results in a different offset. Has anyone seen this on his SRM?

 

If Ergomo need to install my Ergomo and the entire AIS can't work it out (which they couldn't - at least they couldn't make it accurate) and a bunch of French scientists can't work it out, I'm not trusting myself to do it, or my LBS, or pretty much anyone else for that matter.

 

How does being a scientist qualify to install a BB? What´s AIS; Australian Institute of Sports? If yes, do you have a link to their test.

I agree, that the installation is an PITA and really hope that Ergomo will succeed in their atempt to make the installation easier. But I think that readers of this forum might know more about correct installation than most scientist and all points about installation discussed n this forum were confirmed by Ergomo to be relevant.

 

No, if the BB losses are seen by the Ergomo, but not by the SRM, then the Ergomo should read lower (like the PT) rather than higher.

 

Can you clarify your question?

(If you mean that tightening/loosening the crank arm fixing bolt or chainring bolts of an SRM can change the offset, the answer is "yes"...just like tightening/loosening the b.b. changes the offset of an Ergomo.)

 

AIS is the Australian institute. They have some of the best mechanics in Australia. And my experience of scientists is that they are very careful to follow instructions and tread carefully when setting up equipment. Otherwise they would never get valid results. I'm not a bad mechanic, but I'm willing to put it out there that the AIS would install a BB better than me. Some AIS guys tested a bunch of power meters in field conditions. It hasn't been written up completely in a scientific study but some results and discussion were published across several issues of Ride Magazine. In this example, Ergomo was found to overreport by 13% on the average, and not be consistent about it. Powertap and SRM were very good indeed. iBike was 'surprisingly accurate' going uphill, but obviously gets thrown out by a range of factors.

 

Which isn't all that suprising, really - it's accounting for the power required to overcome wind resistance that's tricky.

 

True that. It makes me think, though, if you live near a long, constant climb and only want to use your PM for pacing efforts, iBike might be better than Ergomo and certainly much cheaper. I would want to see more info, but from the AIS test, it tracked the SRM very closely on climbs - not that surprising, as you say.

Of course, when you can buy a powertap pro hub off ebay for 3/10ths of not much, or a new one for a reasonable price, why go for something that doesn't work?

 

That was what I wanted to know, thanks.

 

Thanks Robert and Andy. Procedure worked great. I went with 20kg and the PT was within ~1% for the gear ratios I tested.

greg

 

I "WAS" thinking about getting a PM. My LBS discussed the purchase and recommended that I not waste my money on an Ibike, Polar, or Ergomo. They said that have sent back at least a dozen Polar units for various reasons and have never been able to get an Ergomo working accurately.

They said that if I "really" wanted a PM, get an SRM, but even those have been known to have issues.

At this point, I am really baffled by the whole power meter market and wish that there was an easy answer. Maybe next year.

 

When I read your LBS having problems with about every PM, the question arises if it´s the PM or your LBS causing this problems. It´s like PEBCAK on computers (Problem Exists Between Chair And Keyboard).

 

Unless Quark becomes the first powermeter in history to enter the market with zero issues, I wouldn't bet on it. If you want a powermeter, you're going to have to look at the shortcomings of the few viable systems and how they impact your own situation, and then decide if you can live with them (and if they're worth the money and effort).

If you think that's going to be too frustrating for you (I've been using powermeters for over 6 years, I understand how frustrating they can get), then maybe wait a few more years.

The nice thing about the PMs that have been on the market a while (SRM, wired PT) is that pretty much all the shortcomings are known and either resolved by the company, or there's a fix out there on the internet.

 

Appreciate the thoughts, very helpful and gives me a lot of realistic information.

With respect to the "other post", there is no one better IMO, than a shop that specializes in training and unstallation of a large amount of power meters. Their experience is of course limited to their locale, but the sample is still significant.

When one shop has to send back numerous units, people would be foolish not to pay attention.

From what I have read, it appears that the most bang for the buck seems to be PT and perhaps the best overall unit may be the SRM.

Thanks folks.

 

I think, "the other post" was coined to me. I did not know that your LBS does sell ant install large quantities of PM. Here in Germany, PMs are not as widespread as in the US. Intriguingly, in the country of SRM and Ergomo, I´m called a geek when talking about the benefits of wattage based training in a forum.