Power2Max Rotor 3D Plus crank based power meter review
Power2Max are a relatively new crank based power meter company from Germany. After testing the Power2Max Rotor 3D Plus cranks, we think there are still a few flaws to overcome before they’re ready to seriously challenge the big hitters in the power meter market.
The meter is incorporated into the crank spider and uses four strain gauges to measure the strain between cranks and chainrings. The values are sent to an ANT+ compatible head unit such as a Garmin Edge or a Bontrager Node and read off as watts.
We were disappointed with the behaviour of the Power2Max on the road, particularly in the first 20 minutes or so of a ride. We found that power drifted as much as 65W downwards during that period relative to a stable reference (PowerTap) while the unit adjusted from a warm house to the much colder outdoor temperatures in winter.
After that it was more stable, but there were still some anomalous drifts and the odd dropout that required a manual offset to be performed. When training time is limited, you want data that you can use from the off and in this regard the Power2Max wasn’t up to the task.
Power2Max acknowledge this issue, telling us the drift is between “2-4 watts per degree” which lines up with what we saw, although the auto-zero will eventually correct this. They say you need to acclimatise the sensor before riding.
If you store your bike inside your flat/house, this won’t be feasible. Similarly if you’re doing a long climb where there’s a temperature change from bottom to top then you’ll need to stop pedaling for two to three seconds at regular intervals for the auto-zero to correct.
We asked Power2Max whether they’d consider implementing a method, such as a Wheatstone Bridge as used in SRMs, to reduce the magnitude of the drift. They said this wasn’t an option, as they didn’t want to compromise on the user friendliness of the meter.
Ease of use is certainly one of the advantages of the Power2Max. It’s relatively easy to install and importantly, maintain, as you can replace the battery and change chainrings yourself without having to send it somewhere to be recalibrated and lose a few weeks worth of power data.
It’s also easy to pair with an ANT+ head unit, taking just a few minutes if you know your way round your computer’s functions. You perform a pre-ride zero offset like you do with all power meters and you’re ready to roll.
Finally, it’s also cheaper than other crank based power meters from SRM and Quarq. Our top end Rotor 3D Plus model costs €1,165 direct from Germany (including cranks, spider and bottom bracket, but no chainrings or head unit). At time of publication, this was equivalent to £1,000.
We’d like to see more reliable, stable data from the Power2Max in future, but we can see there are riders who won’t experience the problems we did, so it’s one to consider.