https://www.bikeradar.com/news/rotor-inspider-power-meter/
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Interesting. I’m an SRM devotee, but I am intrigued about this. I want to see some accuracy and precision data.
Cool to see another spider based power meter hit the market, but I don’t see what this does that a Power2Max NG/NG-Eco for the Rotor Aldhu doesn’t already do.
The more interesting nugget in that article was this:
Chainrings suitable for use with SRAM’s 12-speed road and mountain bike groupsets in either 1× or 2× guises are also available
Could be a money saver for folks with Shimano Cranksets looking to upgrade to AXS, as Rotor uses the same 4x110 chainring bolt pattern as Shimano.
I wonder how this all fits together…
I wonder how this all fits together…
https://forum.slowtwitch.com/...inaccurate_P6971170/
Like apples and oranges, as this has the strain gauges in the spider, not the crank arm. There’s nothing inherently different about measuring torque on a 4-bolt spider vs a 5 bolt spider. SRM has been considered the gold standard for accuracy (if not necessarily value), and they support 4 bolt chain rings. The issue sited in that article is related to the difficulty getting accurate, repeatable torque readings from strain gauges installed on the drive side arms of Shimano 4-bolt hollowtech cranksets, particularly the latest versions which have asymmetrical drive side arms.
I want to see some accuracy and precision data.
Don’t we all…
This is of interest to me. I’m trying to thin out my bike gear collection.
We are thinking the same thing. With a Pyramid Cycle Design 110-144 BCD adapter, this would also work with my track bike. It’d surely be cheaper than adding a Power2Max 144bcd pm to my collection too.
Was just trying to figure out which P2M powermeter can be used with 1x set up with the Aldhu rotor cranks, and saw tis article. Seems to be the answer I’m looking for!
On that note, Rotor says it “stays away from claimed accuracy as there is no standard to compare to that is 100% accurateâ€, but that it “always advises that the calibration system we use has less than +/- 1% errorâ€
This is interesting. We delved into this with Dan on the latest episode of the Zwift Power Up Tri podcast that I host with Matt Lieto. There is some desire to have the UCI step in here (whether or not that’s a good idea is debatable, but the rationale that there needs to be an established standard is justified). As powermeters become more important to the sport of cycling - and they are obviously essential to Zwift, I think that having an SAE-like standard for car power measurement is something that needs to happen. I actually give Rotor a lot of credit for making this statement, though I also do think it’s somewhat misleading as well.
If you do a multi-point calibration with known applied torque at various crank angles, that’s accurate. Now, that’s accurate at the spider (and that does get into the issue of drivetrain losses and whether or not to compensate for them). And other issues.
So it’s both true and not true that you can make statements about accuracy - you don’t need 100% accuracy in order to make a reliable statement. I think it’s more about the open ended nature of what, exactly, accuracy means. A PowerTap hub and a set of PowerTap pedals can (and should) report different power values and both be accurate. So what, in that case, is really “accurate.” Pedals are among the most intriguing to me because of how force is applied. The spider has always seemed to me to be the best place to measure power, but I don’t think it’s only one. But I do believe that anything other than the spider is more complex and potentially “risky.” And good spider-based systems have always been among the most accurate…
The spider has always seemed to me to be the best place to measure power, but I don’t think it’s only one.
It’s the best place, IMHO, for measuring the effective output of the rider. But the rear hub is the best place when looking for power data to use in any power/drag/speed calculations.
There is some desire to have the UCI step in here (whether or not that’s a good idea is debatable, but the rationale that there needs to be an established standard is justified). As powermeters become more important to the sport of cycling - and they are obviously essential to Zwift, I think that having an SAE-like standard for car power measurement is something that needs to happen.
That’s quite interesting. You’d like the UCI to ratify power meter accuracy? Power meters are non essential items for cycling as we know it. Unless they do move into the Esport cycling arena… even then, expecting them to shoulder this is quite the ask.
IMO “accurate” should mean that it’s accurate at the measuring device. Meaning if the PT hub is 2% lower due to drive train losses then so be it. The device should report what it is measuring and let the user interpret what it means to the overall system.
IMO “accurate” should mean that it’s accurate at the measuring device. Meaning if the PT hub is 2% lower due to drive train losses then so be it. The device should report what it is measuring and let the user interpret what it means to the overall system.
I’d like the standard to represent what is assumed - it’s the energy expenditure of the rider. If the hub is 2% lower then factor that into the meter…but drivetrain losses aren’t constant. Failing everyone agreeing on that standard then bodies running Esport cycling events need to standardize where power is measured and adopt that - and only that. 2% (or even 0.01%) will be the difference between a win or a loss in the future on those platforms.
IMO “accurate” should mean that it’s accurate at the measuring device. Meaning if the PT hub is 2% lower due to drive train losses then so be it. The device should report what it is measuring and let the user interpret what it means to the overall system.
I’d like the standard to represent what is assumed - it’s the energy expenditure of the rider. If the hub is 2% lower then factor that into the meter…but drivetrain losses aren’t constant. Failing everyone agreeing on that standard then bodies running Esport cycling events need to standardize where power is measured and adopt that - and only that. 2% (or even 0.01%) will be the difference between a win or a loss in the future on those platforms.
I don’t think the device itself should ever factor any assumptions into it because of the non constant nature of those losses. Some people want to know the energy expenditure of the rider but others want to know the power being applied to propel the bike forward (ie. measuring cda for aero testing)
In the case of Esports, let the platform adjust accordingly. ie. you are running a PT hub, you get a 1% boost. Running pedals, nothing for you!
…Power meters are non essential items for cycling as we know it.
No they aren’t. They are now an essential tool for training. This request apparently comes from the top pros who don’t like their power data changing when they change teams. That’s the story I’ve been told (by a fairly reliable source). This is second-hand info, certainly. But I’ve certainly seen an experienced this issue myself having ridden a lot of different power meters.
It makes some sense to me. Having to basically re-benchmark all of your training if you change teams is a big issue. I think you could see this most obviously in that Sky was sponsored by Stages, but all the riders were using SRM…
…Power meters are non essential items for cycling as we know it.
No they aren’t. They are now an essential tool for training. This request apparently comes from the top pros who don’t like their power data changing when they change teams. That’s the story I’ve been told (by a fairly reliable source). This is second-hand info, certainly. But I’ve certainly seen an experienced this issue myself having ridden a lot of different power meters.
It makes some sense to me. Having to basically re-benchmark all of your training if you change teams is a big issue. I think you could see this most obviously in that Sky was sponsored by Stages, but all the riders were using SRM…
That would have been great in my few years! Year one, we were on Rotor dual power. They were good but the next year, we switched to Stages, which read significantly lower. I remember a very heated debate during a team camp because some riders were upset at the low numbers and other didn’t understand the “problem”.
Switching power meters over the years, doesn’t really do anything positive for the historical data either.
We’re talking about different things now. Wheels are essential, so the UCI get involved. Frames, those too. They have UCI certification. Asking the UCI to get involved in power meters is like asking them to certify GPS units tracking time and distance correctly. Power meters are non essential. Weren’t the UCI throwing around the idea of banning them?
In regard to why we need accurate power, I agree. It’s something I deal with on a daily basis. Seeing a Shimano based L/R unit mentioned as a source of ‘inaccurate data’ isn’t news to me (nor to the manufacturers who use those cranks as power meters).
It’d be great to see a certification process in place to ensure standards are met.
My point is it’s a stretch to get the UCI involved.
What do you think UCI could/would do with something like a Stages, or any other Left Only meter? That’s not a calibration issue, it’s an issue of only measuring half of the data and guessing at the other half.
What do you think UCI could/would do with something like a Stages, or any other Left Only meter? That’s not a calibration issue, it’s an issue of only measuring half of the data and guessing at the other half.
I don’t have time to solve the problem here and now… it’s something I’d love to be across. But current Shimano based L/R meters have more issues than just the left only debate (50/50 assumption).