For many seasons, Shimano has watched aftermarket brands create power meters with its cranks. It began with SRM, then hit high gear with Stages Cycling, Pioneer, 4iiii’s and others. Stages Cycling is the biggest buyer of Shimano’s left crank arms in the world. That may all change now. Shimano’s long teased Dura-Ace power meter is finally available this month.
Based on Shimano’s 9100 crank set, Shimano’s Dura-Ace power meter, 9100-P, is similar to Pioneer and Stages dual sided meter, in that it is based on strain gauges placed on the crank arms, rather than spindle or spider based. But, unlike those two systems, Shimano’s system is wired between the two strain gauges, while wireless to head unit via Ant +.
The wire runs through the spindle, where Shimano’s rechargeable battery is housed. According to Shimano, some World Tour teams they contacted asked for a system that was more robust and reliable than what they had been using (of course Shimano declined to tell PELOTON what teams those were or what systems may have proved unreliable). Shimano’s answer, much like its electronic groups, was to wire the system together, at least as much as was practical. This does mean a cheaper, single leg unit is unlikely anytime soon. The meter adds 70grams to a set of 9100 cranks and hits the industry standard of +/-2% accuracy. The 9100-P does use a frame fixed magnet, unlike some other systems which have done away with it thanks to accelerometers. As for frame compatibility, Shimano looked at bikes with chain stay mounted brakes and feels confident its power meter can clear any of those bikes using Shimano brakes.
Riders can expect to get 300 hours out of a fully charged Dura-Ace 9100-P power meter, but will have to make sure they don’t misplace the special magnetic charging cord – no Di2 charger or mini-USB here. Shimano did it to ensure weather proofing, but it does mean another charging standard you’ll need to put into the rotation. It transmits to head units in ANT+, but does have Bluetooth connectivity to talk to your smartphone for diagnostics and zero-offset. Shimano has no plans to update the 9100-P’s firmware to transmit power data to head units though Bluetooth. The cranks can also be zero-offset by pressing the button on the exposed power meter casing by the chainring or with the typical head unit method. Cranks at 12 o’clock, please.
With Shimano’s electronics experience making this power meter was really an easy task. Not only did the brand’s Di2 experience payoff, its e-bike experience was invaluable. The torque sensors used in the Shimano STePS e-bike motor used to determine the level of assist crossed over nicely and were initially used in the pedal analysis system created for Shimano’s fit brand, bikefitting.com, fit bike. The bikefitting.com system provides a massive amount of data about pedal stroke. Much of that could be squeezed out of the 9100-P, but for now Shimano plans to just deliver the metrics most dual sided sensors do like balance and efficiency. While pedal vectors similar to Pioneer’s unit could be displayed and recorded Shimano has no plans to do so.
Shimano Dura-Ace 9100 cranks come in a wide array of sizes and so does the 9100-P power meter. 165/167.5/170/172.5/175mm will sell as full cranks while 160/177.5 and 180mm as arms only. Since the meter is crank based changing chain rings does not affect the system’s accuracy. Complete with rings the 9100-P sells for $1500, arms only are $1350. For comparison: Stages new dual sided system is slated to cost $1300 and adds just 35grams. Pioneer’s 9100 dual leg system is also $1500 and adds 62grams of weight. As of now, Shimano has no plans to stop selling cranks to aftermarket brands like Stages and Pioneer.
Look for a long term review soon in the pages of PELOTON Magazine. For more info now check out duraace.com