Sea Otter: Rotor launches axle-based INpower power meter

Compatible with mountain and road cranks, runs on AA battery

Components Sea Otter Classic

2015 Sea Otter Classic

Battery replacement is simple. Just one AA battery and you're good to go.

Battery replacement is simple. Just one AA battery and you’re good to go (click to enlarge).

The company best known for its ovalized chainrings is making a continued push into the power meter market. This week, Spain-based Rotor Bike Components launched INpower, an axle-based power measuring device for road and mountain bikes that runs on an easy-to-swap standard AA battery.

Highlight features include tool free battery replacement, 30mm axle length, and electronics that are completely sealed inside the device. This goes in contrast to most other power meters currently on the market, be them hub, crank, spider or pedal based. Added weight is claimed to be less than 100 grams. Data is transmitted via ANT+, meaning it will work with most data-capture devices on the market, including Garmins.

By integrating inside the bottom bracket, INpower is protected from shock, crashes and outside contaminants, and it maintains the users bike’s original aesthetics. The only really noticeable change is a small fin at the end of the left crankarm, which houses the device’s antenna.

We did a test session aboard this Santa Cruz Blur LTC.

We did a test session aboard this Santa Cruz Blur LTC (click to enlarge).

The INpower device uses opposed strain gauges in the left crank-arm only to constantly measures power, not just 1-2 times per crank rotation. This, says Rotor, is particularly important for users of ovalized chainrings, which otherwise often return higher power numbers when output is only measured incrementally because rotation speed is not constant.

Left side only INpower cranks start at $779, with complete set-ups starting at $939. Rotor also announced price reductions for its existing power meters, Power and POWER LT. ROTOR Power will now be offered for $1,559 (from $2,400), and POWER LT has been lowered to $1,079 (from $1,490).

Because INpower measures data in the left leg, cyclists who already own a current set of Rotor cranks can purchase only the left crank arm and install it themselves with the help of a downloadable multi-lingual user’s manual.

The fin at the end of the crank houses the antenna.

The fin at the end of the crank houses the antenna (click to enlarge).

While power meters have traditionally been the domain of road riders, Rotor is pushing the idea that mountain bikers can benefit, too.

“Mountain bikers don’t always think in terms of power,” said Cameron Chambers, of Podium Performance, a Colorado-based coaching business. “But there is a lot of benefit to be gleaned from this kind of information. Mountain biking has very unique and variable demands that are much different than the efforts required on the road. Power allows you to quantify and identify efforts, become more efficient in your workouts, and stay focused.”

Due to its position inside the frame, INpower is available for any 30mm Rotor crank, be it mountain or road. Besides the usual measured metrics, INpower provides TORQUE 360 and Optimum Chainring Angle (OCA) pedal analysis, which are designed to help users accurately assess force variations in their pedal stroke. These values enable cyclists to best orient their Q-Rings, which have multiple mounting options that can be adjusted based on rider preference and riding style, the objective being to target your most productive zone and remove dead spots from your pedal stroke. Chainrings are available for 1x and multi-ring set-ups.

Added weight is claimed to be less than 100 grams.

Added weight is claimed to be less than 100 grams (click to enlarge).

“We wanted to create a power meter that overcame current trends in power meter technology and could be transferred to other disciplines,” said Pablo Carrasco, Rotor’s head of research and development. “At the same time we wanted to leverage the benefits of Q-Rings and build a power meter that’s fairly simple to use.”

Here’s a rundown of key features:

  • Runs on double AA battery, claimed 300-hour run time
  • Tool free battery replacement
  • Measuring device housed inside axle
  • Power measured on left only, then doubled
  • 30mm diameter axle that’s compatible with almost all standard frames on the market. The notable exception is BB90 and BB95, meaning Trek
  • Torque effectiveness and pedal smoothness determine total torque versus positive torque and average power versus maximum power
  • Works with road cranks, including Rotor Flow crank, making it an aero power meter
  • Used by MTN-Qhubeka WorldTour team among others

For more information visit

This article is part of Mtbr’s coverage of the 2015 Sea Otter Classic in Monterey, California. For more from Sea Otter CLICK HERE.

About the author: Jason Sumner

An avid cyclist, Jason Sumner has been writing about two-wheeled pursuits of all kinds since 1999. He’s covered the Olympics, Tour de France, MTB world champs, and dozens of other international cycling events. He also likes to throw himself into the fray, penning first-person accounts of cycling adventures all over the globe. Sumner has also done extensive gear testing and is the author of the cycling guide book "75 Classic Rides: Colorado." When not writing or riding, the native Coloradoan can be found enjoying life with his wife Lisa and kids Cora and Tommy in and around their home in the MTB Mecca of Crested Butte.

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  • ziscwg says:

    I like it, but Stages is cheaper and lighter. It’s also avail for mtb.
    If they could have just had it a BB with your own crankset, I think they would have something.

    I think it’s good to have choices to keep the current PM king, Stages, on their toes.

  • Don says:

    Seriously, no better than Stages. What everyone is looking for is a power meter that will work with carbon cranks and 1x, without the weight penalty and being restricted to one wheelset like you get with a Powertap, or the insane cost of an SRM.

    C’mon people, get on it.

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