POWER METER - POWER TAP 3 de 6

The PowerTap has been around since the the turn of the century, appealing due to a significantly lower pricepoint than the SRM and to those riders who prefer the idea of a wheel rather than crank based device. PowerTaps have been adopted by a number of professional cyclists, most visibly making their way into the professional peloton via Garmin Chipotle, and continue to enjoy a significant following. This isn't a system that can be calibrated in the field, we also hear of a few more issue viz-a-viz reliability and longevity (in fairness we compare to the gold standard SRM), but let's be clear - it does the job of accurately measuring power and gets you up and running with power and without breaking the bank.

Appearance
Manufacturers Site	www.cyclops.com
Data Measured	Speed, cadence, HR, power, ride time. Max and average (as applicable). Kilojoules energy spend.
Variants	Several units having different weights and price points, upto the lightest G3C featuring ceramic bearings. Bought either as a stand-alone hub for building into your preferred wheelset (with a choice of hole counts) or integrated into a wheel set.
Power Unit	Integrated into a rear hub. 8 strain guages. Integrated cadence detection.
Head Unit	Compatible with ANT+ computers. Cyclops themselves make and recommend the Joule 2.0 computer. A Joule 1.0 (smaller, better for racers) and Joule 3.0 (larger) also exist.
Installation	Assuming the rider takes delivery of a ready built wheel installation is as simple as swapping this in to the desired bike.
Software	Cyclops supply PowerTap units with their proprietary "PowerAgent" software. Many users have purchased WKO+
Reliability	We have seen more reports of failed PowerTaps than any other power meter. It seems there comes a point in the life of every PowerTap when the "torque band" fails, the power readings become notably unrealistic, and a return-to-factory service is required.
Price	The PowerTap G3 hub costs £975. Add wheelbuilding or purchase with a basic alloy wheelset for circa £1125. Add a pricey £360 for a Joule 2.0 head unit, £165 for the Joule 1.0 or £200 for a Garmin Edge 500. Minimum "on the road price" for a G3 is therefore £1140.
Service	We have read reports of fast, efficient service whenver a unit needed recalibration or repair.
Accuracy	Claimed accuracy is +/- 2% assuming good calibration (at the factory only) and setting of the "zero-offset" before every ride. There is an "auto zero" function.
Calibration	Not a DIY procedure, requires return to a service centre. See our Power Meter Calibration Calculators for the "stomp" test which is a gross error check.
Weight Penalty	The G3 hub, the lightest of the range, weights in at 325 grams. A Dura Ace 7900 rear hub weighs 254 grams. A weight penalty of 71 grams is impressive.
Who uses one?	The PowerTap was most conspicuous in the professional peloton as an accessory of the Garmin Chipotle team.
Top Reviews	Cyclops (Review Links) Robert Chung (accuracy tests) Bertucci et. al (accuracy versus SRM