BikeErg - How accurate and precise

[Livio Livius]

I am wondering as we see a lot of debates on powermeters and Bike Erg's like (Tacx, Wahoo, etc) how accurate and precise the C2 BikeErg is. Is it different from C2 rower due to belt driven vs chain driven? Or can we state that C2 rower Watts are as accurate and precise as the BikeErg?

[johnlvs2run]

can we state that C2 rower Watts are as accurate and precise as the BikeErg?

Yes, because neither one of them are accurate, especially not compared to power meters.

[Livio Livius]

Can you explain why you think that powermeters are more accurate?

[CaseyClarke]

There are dozens of power meters out there on the market, so I think if you're going to compare BE accuracy to a PM then you need to compare to a specific power meter, rather than just say 'power meters' in general.

I've used half a dozen different BikeErgs and they all perform exactly the same in terms of wattage. I've used more than half a dozen different power meters and it's fairly common to see variances of up to +-10%.

Here's an article about it:
https://www.cyclingweekly.com/news/late ... ers-330322

[jamesg]

https://en.wikipedia.org/wiki/Strain_gauge

We can read all about strain gauges, presumably used in powermeters, here. They are sensitive to all sorts of ambient conditions, but if pro cyclists use them in the rain and cold seen this week in Italy, as well as the extreme heat we now hope for, no doubt they have their value (and price).

The C2 erg type machines do not have these items, needing only time and flywheel speed. Accuracy of these parameters is hardly a problem nowadays.

[Livio Livius]

But I also saw a study C2 rower underestimating power with 25watts. Will see if I can find it.

[johnlvs2run]

Power meters are designed to accurately measure wattage output.
The C2 monitors are reliable, as they show consistent readings for each given machine.
However, showing reliable readings is not the same thing as being an accurate wattage measurement.

[Livio Livius]

So are we talking about precise than instead of accurate?

[Nicola]

I asked about accuracy to C2 support and they told me that it’s a 2% error, like other systems.
In theory it’is easier to calculate power from flywheel devices because we know all the variables (size, velocity, rpm and drag) instead of others direct powermeters.
In my experience I tried Lemond revolution trainer (same concept) and power was accurate and precise.
During next week i’ll Check it with powermeter pedals.