Crank and pedal based power meters usually dont give accurate power readings when used with oval chainrings. Quick googling suggests Team Sky still use Stages

Crank and pedal based power meters usually dont give accurate power readings when used with oval chainrings. Quick googling suggests Team Sky still use Stages as a power meter, and Stages say on their website: "Through our own testing, and using a hub-based meter as a control, we conclude that there will be a 4-5% increase on the readings from a Stages Power meter when used with a non-round chain rings." [1] [1] http://support.stagescycling.com/support/solutions/articles/1000158537-can-i-use-the-stages-power-meter-with-oval-or-osymetric-chain-rings- http://support.stagescycling.com/support/solutions/articles/...