Rotor launches INpower spindle-based power meter cranks

Road or MTB, near-universal fitment, easily transferrable, handy AA batteries

This article originally appeared on BikeRadar

Rotor is supplementing its existing crankarm-based power meters with a new single-sided system called INpower that's built within the company's 30mm-diameter bottom bracket spindles. It weighs less than 55g, it's less expensive than Rotor's dual-sided system, there's a wide range of crankset options (including for mountain bikes), and it even uses refreshingly common (and cheap) AA batteries.


Rotor's new INpower power meter can be added to nearly any of the company's cranksets

Key features:

  • Spindle-based direct-measurement power meter with dual strain gauges
  • 30mm-diameter UBB aluminium spindle
  • 300-hour claimed run time
  • Requires one AA battery
  • Roughly 50g of additional weight
  • ANT+ wireless transmission
  • US$959-1139 / £TBC / €TBC / AU$TBC (left and right crankarms, spider, and spindle)
  • US$779-869 / £TBC / €TBC / AU$TBC (left crankarm and spindle only)
  • May availability

Tucking all of the critical bits inside the spindle offers up a number of practical advantages over a spider- or pedal-based power meter system. The axle-based format is largely protected from weather and impact, it's visually inconspicuous, and very compact. The cylindrical form factor uses just one AA battery for up to 300 hours of ride time – and when a replacement is needed, they're extremely easy to find.


Save for the small ANT+ antenna, which is affixed to the end of the non-driveside crankarm, all of the power meter hardware is enclosed inside the spindle

Since Rotor uses the identical spindle for all of its 30mm-diameter UBB (Universal Bottom Bracket) cranksets, this also means that the vast majority of the company's cranks now have direct-measurement power as an option, either as a complete crank or an add-on spindle-plus- crankarm subassembly for existing owners – and it's easily transferable. The UBB spindle will work with nearly every bottom bracket shell on the market, too, including standard BSA and ITA threaded, BB/PF30, PF86/92, BB386EVO, and BBright; the only major exception is Trek's BB90/95 system.

In addition to providing the usual on-bike power metrics, INpower also offers some unique graphical analysis tools when used with the associated desktop software or smartphone app. For example, Torque Effectiveness compares your total torque with your positive torque (essentially telling you how much your upstroke leg is fighting against your downstroke leg) while Pedal Smoothness tells you in real time if you're pedaling in circles or squares. Finally, the Optimum Chainring Angle function is specifically tailored to Rotor's elliptical Q-Ring chainrings, giving users precise guidance on how the rings should be oriented for maximum benefit.


The software offers up some rather interesting features to help improve your pedaling technique

In the event that other features are developed later, the system can be updated over the air via an ANT+ dongle.

While the new INpower certainly sounds appealing, there are some downsides. As with any spindle-based system, INpower only directly measures the output of your left leg; total power is merely an extrapolation that assumes equal output from both legs. In addition, the system is ANT+ only (as in there's no Bluetooth functionality) and the software won't work with Apple OS X operating systems. Most critically, the design is brand new so there's no way to predict long-term reliability.


The system is powered by a single AA battery, which resides beneath a tool-free cap on the non-driveside

Regardless, one immediate benefit of the new INpower system is that it's prompted Rotor to drastically lower the prices of its other power meters. The dual-sided Power drops to US$1,559 / €1,299 (from US$2,400 / €1,699) while the single-sided Power LT is now US$1,079 / €899 (from US$1,490 / €999).

We'll have a production sample of the new INpower in a couple of days so we expect to answer some of these questions shortly. 

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