Utilizing a slim, hidden design similar to the new dual-sided add-on power meters created for Shimano Dura-Ace, the all-new 2018 Specialized Power Cranks use 4iiii technology to deliver dual leg measurement. The design is unique to Specialized, and benefits from unique testing protocols done inside the bike brand’s Win Tunnel.
They say they tested the already accurate claims provided by 4iiii with multiple riders on a custom cycling treadmill (called…wait for it… the WinMill) placed inside the wind tunnel. They also tested other power meters and simulated various conditions, with the result being 4iiii as the winner to provide their power meter components on the new S-Works level crankset. Earlier this year, they began testing under Peter Sagan and the Bora-hansgrohe and Quick Step pro teams.
The slim transmitters are placed on each arm, offering dual-leg measurements and the complete power profiling that 4iiii has to offer. This includes the usual output numbers plus things like axle strain, which is measuring the rotational and other forces you’re putting on the cranks -not just pushing down or pulling up- which is how they arrive at an impressive +/-1.5% accuracy claim.
What makes these even more special are that they’re the first carbon fiber crank arms to get the add-on power meter treatment. The units are waterproof and come with the tool for cover removal, which is necessary for coin cell battery swaps (sorry, not rechargeable).
They +/-1.5% accuracy was verified in their own Win Tunnel and at Locomotion Lab in Boulder, CO. They transmit via Bluetooth and ANT+, which also allows app-based updates and calibrations. It’ll come with a 110bcd spider as standard, with a 130bcd spider available separately. Claimed weight is 440g (without chainrings, 172.5mm arms) thanks to hollow carbon fiber arms, a carbon spider and oversized 30mm alloy spindle (BB30/PFBB30/OSBB compatible). They recommend using only the Specialized/Praxis chainrings in 52/36 and 50/34 combos. Arms are available in 165, 170, 172.5, 175 and 180 mm lengths.