Stages Cycling crank-arm based power meter - first look
70g unit measures force applied to non-driveside crank arm
by Timothy John
Power meters are becoming increasingly popular as a method of measuring performance.
The price, however, of the competing systems, whether they be crank-based, pedal-based, or hub-based, can be prohibitive.
Colorado firm, Stages Cycling, is the latest to enter an increasingly crowded market with a power meter mounted on the inside edge of the non-driveside crank arm, and sold with the arm at a starting price of £599.
The unit, which we measured at 70mm x 28mm, contains a strain gauge to measure force applied to the crank arm, an accelerometer to measure cadence, and two devices to communicate electronically, via ANT+ and Bluetooth Smart, with bicycle-mounted computers like Garmin's EDGE. Oh, and a CR2032 battery.
The final piece of technology mounted in the 70g unit is a temperature sensor. Stages make great play of their power meter's ability to recalibrate 'on the fly', without the need for rider interventions like pedalling backwards. It samples the temperature of the crank arm every 20 seconds and automatically recalibrates, apparently: a useful function, they say, if riding from Alpine valley floor to summit.
By locating a power meter in only one crank arm, the system is prevented from offering left and right power outputs, a possible disadvantage for riders training for a more balanced output.
Manual recalibration of the Stages Cycling power meter is recommended if the retaining bolts at the top of the crank arm (those used to grip the BB axle) are adjusted by holding the crank arm vertically. No rider data is required. Recalibration takes place via an i-Phone app, based on the IOS7 platform. Firmware updates will come via IOS7, too. There is currently no Android support.
Stages Cycling sell the power meter and non-driveside crank arm - alloy only - as a package, currently available in Shimano. A 105 crank arm and power meter will sell for £599, or £699 for Ultegra 6800, and £799 for Dura-Ace.
From January, Stages pledge to introduce a system for FSA's alloy crank arms, compatible with their Mega EXO, GXP, and BB30 bottom brackets.
Price: £599 - Shimano 105; £699 - Shimano Ultegra; £799 - Shimano Dura-Ace
Website: Stages Cycling
UK distributor: Saddleback