Rotor's INpower REX 1.1 Boost Power Meter Crank Arms beg on immediate question: What kind of mountain biker wants power measurement? The answer: Us. And by "us," we mean roadies-cum-endurance hammerfesters and enduro shredders who relish the pain of climbs as much as the pleasure of dropping in. Plus, we admit that it's just a lot of fun to be able to record, parse, and analyze pedal stroke data—a fact that's even more true on the trail, where constantly changing gradients and terrain mean power output isn't as simple as push pedal; go up road.
Instead of the dual-leg, eight-gauge approach of the 2INpower model, the INpower meter uses four gauges to measure power and pedal stroke data coming through the left crank arm only. The strain gauges themselves live in the spindle. This provides more protection against the elements (be they rain, snow, or trail furniture encountered during the occasional user error), and it also helps to tidy up the crank's silhouette by eliminating bulbous protrusions at the crank arm/chainring interface—of course, the grooved crank arms and (should you run them) Rotor's iconoclastic chainrings will still stand out.
As with other power meter cranksets, the INpower's four strain gauges are all spindle-bound and it's equipped with an accelerometer to read cadence; unlike other meters, Rotor's design measures cadence over 500 times per pedal stroke. While the benefits of mapping minute changes in cadence over each leg's power production are immediately obvious to any data obsessive, the potential is magnified exponentially when paired with Rotor's Q-Ring system. It helps you chart the most efficient Q-Ring orientation possible to capitalize on the strengths of your pedal stroke while mitigating the weaknesses. The crank arms work just fine with traditional round rings, but adding Rotor's Q-Rings takes full advantage of the system's potential.
The INpower transmits data via ANT+ Smart protocols, so chances are good that it's already compatible with whatever head unit you're running; however, it's a bit more limited on the bottom bracket front. The INpower 3D30 has a 30mm spindle, so it may take some adapting to adapt it to your shell, but it's compatible with English and Italian threaded, BB86, BBRight, BB386EVO, and—of course—BB30 and PF30 bottom bracket shells. The unit's 300-hour ride time relies on AA batteries, so re-upping is never an issue. Rotor also provides a seamless data upload and management interface by partnering with TrainingPeaks.
The crank arms themselves are the product of Rotor's Trinity Drilling System (TDS), a method of hollowing out the cranks, which reduces weight and maximizes stiffness. Unlike traditional hollow crankset design, TDS involves drilling three channels from the pedal to the spindle. While these holes remove excess material, they also leave behind two thin walls, making them stiffer than the design of a single hollow chamber. The TDS creates a maximum strength-to-weight ratio, and the arms were constructed using a new 7055 alloy, which is both lighter and more durable than the more often used 7075.
- Take the power to the trail with Rotor's mountain crank
- Four strain gauges extrapolate total output from left crank arm
- Charts cadence with internal accelerometer
- Electronics housed in spindle to protect from elements
- Replaceable AA batteries ensure a re-upping isn't a chore
- Lightweight, stiff alloy construction proven on the biggest stage
- Pair with Q-rings for maximum training metrics
- Partnership with TrainingPeaks makes for seamless data management