For a long time, experts debated whether it was even possible to measure a cyclist's performance directly on the pedals: Computer specialist O-Synce presented a concept in 2010, Garmin bought into Metrigear, who had already worked on a version for Speedplay pedals many years earlier, and Look also showed a pedal-based system in collaboration with Polar. The latter have now launched the first functioning system on the market. The Kéo Power measures power directly where it is fed into the road bike system: at the interface between rider and bike.
Eight strain gauges on each pedal axle register the deformation caused by the load on the pedal; the power is then calculated from the data. The pedals are hardly distinguishable from standard Kéo pedals; the Polar computer supplied is also rather inconspicuous. Only the conspicuous sensors on the crank arms, which transmit the data to the computer, give away the technology inside. At 383 grams (without computer), the system is probably the lightest power measurement system on the market - considering that the pedals are already included.
Assembly is relatively simple. The pedal axle must be aligned with the crank arm and secured with a lock nut. The sensors, which also contain the batteries, are inserted into the axle from the rear and secured to the crank with cable ties. In addition to the pedal spanner, an 18 mm open-end spanner and a small pair of pliers are required as tools. The special spanner for aligning the axle is not absolutely necessary, but is advisable.
Nevertheless, the system is the most flexible power measurement to date: you are not restricted to specific cranks or a wheel, the pedals can be fitted to almost any bike within five minutes, provided its cranks have a standard pedal thread and are no thicker than 16 millimetres. With some cranks, the right-hand sensor can rub against the chain in the highest gear. So far, we have only noticed this on Shimano drivetrains; there is sufficient space on Campagnolo, SRAM, FSA and Rotor cranks.
A single button on the left-hand sensor is used to set the crank length, pair with the computer and calibrate the zero point. Commissioning works straight away, the calibration with a PowerTap hub and a Power2Max crank delivered plausible watt values in all power ranges. The displayed values are slightly higher, which may be due to the fact that - in contrast to the other systems - measurements are taken exactly where the power is applied. However, it is not possible to judge which values are more accurate without complex measurement procedures.
A new feature is the option of displaying and analysing the power components of the left and right leg separately. The data is not transmitted using the ANT+ standard, but via Polar's W.I.N.D. protocol. This means that only Polar computers (from CS500 upwards) and the company's own software can be used; the heart rate and speed sensor must also come from Polar. The system does not offer automatic zero correction; you have to calibrate manually - for example in the event of temperature fluctuations - which takes the system around ten seconds.
The Look Kéo Power offers all the functions you would expect from a power meter. It is comparatively light and extremely flexible. An endurance test will have to show how robust the sensitive technology is in such an exposed location. The price had not yet been finalised at the time of going to press; according to current information, it should be around 1,700 euros.
PLUS lightweight; quick to fit; left/right leg display
MINUS not ANT+ compatible; no automatic temperature compensation
Reference/Info www.grofa.com
