Rotor Power Meter/Garmin 810

New toys

Chad Butts just got Rotor’s new Power Meter Cranks so I stopped by his studio while Mark Purdy installed it. Here’s a quick first look at this new power meter.

The Rotor retails for $2350, which puts it between the other two major crank based power meters, SRM and Quarq. Its major feature is that it’s essentially two power meters, with 4 strain gauges on each crank arm (SRM’s and Quarq’s have strain gauges in the spider). This is supposed to make it more accurate, as well as provide three additional pedal technique metrics: left/right balance, torque efficiency, and pedal smoothness.

Left/right balance is self explanatory. Torque efficiency measures how well you pull up on the upstroke (the cranks can tell which direction you’re deforming them, so they can tell you if you’re actually fighting yourself on the upstroke). Pedal smoothness is how ‘round’ your pedal stroke is, or how well you apply power in the dead spots.

You need to know where the cranks are for that data, so the Rotor has accelerometers to report its orientation. The accelerometers also provide cadence data – gone are the SRM/Quarq magnets. This may seem trivial but Mark says he spends a lot of time fine tuning magnet position for clients so their SRM’s and Quarq’s work properly.

Each crank arm has its own set of strain gauges and battery. The left ANT+ pod transmits to the right pod, which then sends data to the head unit.

The spider has two sets of holes so users of Rotor Rings can fine tune their orientation. Additionally the mounting holes in the rings are offset so that turning them 180 degrees gives you another half notch adjustment.

Here it is with rings mounted. Note the offset in the mounting hole options.

And here it is with the SRM that came off Chad’s bike, which doesn’t have the micro adjust spider.

Mark requested (demanded?) an action shot.

Here’s Garmin’s forward mount. The locking mechanism can rotate 90 degrees if you prefer your data in landscape.

And there’s the money shot on the new Garmin 810! Mark hand cranked out 22 mighty watts for a perfect 100% – 0% imbalance! I’m not sure if Garmin’s firmware supports torque efficiency or pedal smoothness yet, we’ll check back with Chad later after he gets a chance to ride it. The 810’s big new feature is its ability to pair with a smartphone via Bluetooth and then stream your data live. Check it out in this slick video with the Garmin team.

Here’s one of Chad’s ride files, see his comment below.



Jasper Rim

Can you run Praxis or other aftermarket chain rings with the rotor power meter or are you limit to rotor rings?

And of course you weighted it before mounting?

Clement Skidmark

The real question is, will Chad be able to retain his Harlem Hill Strava KOM status throughout ’13?

Andy Shen

You don’t have to use Rotor rings and there was no weighing unless Mark and Chad did it before I got there.

Danato Seattube

Is this power meter/crankset available on the market now? I’m looking to get one as soon as it becomes available to the masses.

Mathis Wave Ring

Andy, do you think Rotor is has the newest and best power technology on the market and did it live up to all of the hype?

Any additional info would be greatly appreciated
Joe Petrosso
please get back to me,

Chad Butts

Will get back to you on the temp questions but I assume it is still affected and you should always calibrate because it is still a strain gauge and the cranks will get cold. As far as the Cadence issues go it seems to be more related to Garmin or computers picking up the signals given the fact that when you upload files all the cadence seems to be there despite seeing a bunch of cadence drops. My file shows the one section but I think that was mostly me messing with my shoes. I uploaded another file from a ride this weekend which showed a lot of fluctuations at certain parts and after uploading did not see it. So the data is there but for some reason the Garmin is not displaying it. I had it set to 3s average and at some points it fluctuated a lot despite a steady power compared to my SRM.

Andy Shen

FWIW I’ve been seeing a lot of drops with my Quarq/Garmin 500 indoors. I was positive it was the Quarq but to check I tried using an iBike simultaneously and there were no drops at all, so there might be something going on with Garmins.

Lorenzo Plug

There is a known issue with power recording on the new garmin 810 and 510 models. At low cadences there are intermittent half power readings recorded due to the way it handles event based power data from crank power meters when a full crank cycle takes longer than 1 sec (i.e <60rpm). Should 'hopefully' be fixed with a future firmware update. 'Old' edge 500 should be fine though. These such glitches are why many serious power users rely on the SRM PowerControl.


That’s why it would be nice to know how often the Rotor unit transmits the cadence to the head unit. Is it event based? From what??

Didn’t the original AIP cranks transmit 360 times?

Chad Butts

Hey Lorenzo,
After about a month of use with the Rotor Power here are my experiences:

1. Initially the calibration procedure was cumbersome, sometimes working and sometimes not. After updating the Garmin 810 to the new firmware it has worked fine according to the manual. You have to run through two calibrations, one for each arm.

2. The battery levels seem to be at half power since I got it. I have not replaced the batteries yet but on a scale of 0-10 mine was a 6 when I got it (10 fully charged). It is still at 6 after 1.5 months.

3. Once in a while there is a cadence drop and the Garmin unit zero’s out for a split second but honestly it happens once or twice a ride that I have noticed. Somehow I feel it is a signal issue but I have no idea. I will have Andy post a picture of the data from my ride last night. 1H ride, no smoothing. You can see one major section but that is where I was adjusting things on the bike and not pedaling. I did see 3 occasions where the power suddenly went to 0 for a brief second but as you can see in the data file that in no way affects the data. I looked at my other files and same thing, the cadence issues are so infrequent I can’t see how it would affect the overall ride at all. I have been reading about the cadence issues on the forums etc. but have not paid any special attention since I don’t think it has any meaningful affect on the ride files.

4. I have been using the QXL rings on a MAS spider…not sure this matters at all but I know the MAS rings now have a cut out, possibly for signal issues (rumors on forums). Not sure if there is a difference with a regular Q ring, Aero Q ring, or QXL ring.

5. Relative to the SRM the only drawbacks are having to use the Garmin and the calibration fuss every other ride or so but other than that it reads the same as my SRM vs. computrainer vs. feel etc.

Overall I am very happy with it and it functions fine. My only issue is the fuss of using a garmin vs. PC7. Sometimes more basic is better but I realize I have other options than the Garmin but the real time tracking was pretty cool!

Lorenzo Plug

Hey Chad thanks for the update! According to the rotor manual you only need to calibrate it once (after fitting and changing pedals). Apparently this is due to the fact that it is supposedly ‘immune’ from temperature changes which affect the zero offset (calibration in garmin speak) of other power meters. Do the calibration numbers change each time you do it? Might save you a bit of stuffing around if you can set and forget. Battery might be showing low if the ambient temp is cold? Agree the PC7 has fewer bells and whistles than the garmin, but it is bombproof and displays basic data well. Would be great to see the ride file – easy way to do it would be to post the garmin connect link for the ride. Happy days!Cheers!

Lorenzo Plug

Oops just noticed the WKO chart Chad. I assume it was on a trainer yes? I can see a few unusual downward blips in cadence (and power) at 30sec, 1min, 5min20, 16min and 31min? What we don’t know is if they were deliberate changes in cadence/power or not. I assume for instance that you didn’t actually tank half way through your interval @16min for instance? And at 31 min it looks like the signal dropped in and out for about 20 sec? Otherwise looks AOK.BTW I have a rotor power on order and I hope these little teething issues are quickly sorted. It is great to have another power meter option in the market.

Lorenzo Plug

Any update on real world use from Chad? How does it compare to the gold standard SRM which it replaced? Apparently there have been some issues with early units and cadence measurement that cause intermittent drops in power. Have you noticed this behavior on the road or in downloaded files?

Chad Butts

Ha sorry, I thought that was short.
This you should follow, “me think Rotor good, buy many”

“I’ll have the roast duck with the mango salsa.”

Goro Downtube

Title says it all really. Have Rotor put the power meter on hold as I can’t find them available anywhere….

Lorenzo Plug

Yep, pretty scarce at the moment. Lots of demand and supply is only just enough to meet pre-orders, hence none actually in stock for any new orders. Better that they take their time to get any early manufacturing issues sorted, and address any issues with firmware. My guess is maybe 3-4 months until they become more widely available. I’ve got one on the way now, but I ordered back in November.



I am about to buy a powermeter. I am between two: Power2max and Rotor Power, and I don’t know which one I should take.

Power2max is cheaper and it seems it works very well. I read some issues with the Rotor Power (although I didn’t understand them very well) and Rotor is more expensive, but on the other hand it seems it is more sofisticated and you can’t get more information. I also like the fact that it has a power meter in each crankarm and this could mean, you can have more accurate information and furthermore, you have other options as torque effiency and the pedal smoothness.

Please, could anyone help me with this?

Schiatta Clearcoat

Power2Max is the one to get, they have just dropped their prices even further. A full crank based power meter for 1100$ including a Rotor crank 3D crank, just cant beat that price or quality. Made in Germany!
All chain rings accepted without any issue!


Thanks for the quick review and awesome pictures. I am thinking about getting the Rotor Power.

Any aftermarket device out there that measures “torque efficiency”?

Thomas Butyl

i had a power2max 2013 edition with rotor 3df crank for 845 euros. i was very very pleased with the unit. i changed to rotor power just for the 110 mas spyder and 130grams lighter than the power2max.
i payd an extra 400 euros but the result was a little disapointing
i use a garmin 500 edge and i have to calibrate 2 times in every ride scrolling at the menu eash time, and the batteries are wearing down fast enough. then i notices sometimes it blanks out for a few seconds while pedaling ! not very happy for a price abot 50% higher than the power2max….

Luchino Setscrew

Could there be a way to hijack the software on a powercontrol so it will read data from the Rotor power cranks?

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