Rotor launches INpower spindle-based power meter cranks

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With the introduction of INpower, Rotor now has both crankarm-based and spindle-based power meter options(Image credit: James Huang/BikeRadar)

This article originally appeared on BikeRadar

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.

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.

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.