Long discussed, and prompting nervousness from other power meter brands, Shimano has finally entered the data-driven market. Closely based on technology from its previously acquired BikeFitting.com business, the new dual-leg power meter packs a number of industry-first features into its new Dura-Ace crankset host. Shimano quickly stated that reliability and accuracy were two key design factors in the new power meter.
The Dura-Ace FC-R9100-P power meter places strain gauges at three key points: one on each hollow aluminum crankarm and a third inside the 24mm steel spindle. Doing things a little differently, the left and right gauges are connected via a wire that runs through the crank spindle. This allows the use of a single battery and less chance of transmission issues.
While Shimano’s own literature doesn’t mention it, we’re told the spindle-based strain gauge provides the impressive vector data that the BikeFitting.com machine has become known for. We originally witnessed the BikeFitting-specific power meter a few years ago, where it was shown that the pressure spots through the pedal could be detected. In turn, providing useful information regarding the effect of cleat position and even innersole type. Whether the data is useful or not to have on a bike or even detectable at all by current head units is perhaps too early to tell.
Upon recently getting our hands on a working prototype (for five minutes…), we received word that the new power meter offers 2% accuracy. While this may seem equal to many other options out there already, we’re told that Shimano is achieving 2% accuracy at 200 and 1,200 watts, and everything in between.
Previously the company had been coy as to where exactly the battery is housed, however, we now know the Lithium-Ion battery sits within the steel axle and should provide over 300 hours of use between charges. Additionally, we can confirm that the hollow crank arms are indeed being used for at least the routing of wires.
Charging the battery will be achieved externally by connecting a sealed magnetic plug to the driveside ‘brain’. It’s a similar technology to that of modern smart watches and should help in making the system truly waterproof.
Shimano has made no comment in regards to a Shimano head unit, but the Dura-Ace power meter will offer both ANT+ and Bluetooth connectivity. While Shimano has not confirmed it, the Bluetooth is more likely to be used for firmware updates and systems checking than live connectivity.
It’s worth noting that the integrated nature of this power meter means it’s an out-of-the-box item only. You won’t be able to fit the technology to existing 9000 or even new 9100 cranksets.
Changing chainring sizes is said to be a non-issue for the new power meter, and it’ll use the same rings as the standard 9100 crank. Shimano has claimed the power meter adds 70 grams over a standard 621 gram 9100 crankset (170mm, 52/39T, no bottom bracket). Pricing is still to be confirmed, with availability scheduled for approximately April 2017.
As it uses an induction charger, the plug is kept completely waterproof.
A special magnetic plug is used to charge the power meter.
A look inside the spindle.
This plastic cap threads into the spindle to keep grease out of the electronics during installation.
A view from the back. The new power offers a slim profile, with the internal wiring making use of the hollow crank design.
The left crank also hides the wire inside the crank arm.
The left crank features a plug to connect in to the battery and communicate with the right.
Another view of the plug that belongs to the left crank.
Due to the plug on the left, Shimano had to redesign its crank bearing preload adjuster. It’s now hollow, with a special tool to adjust it.
Once everything is plugged in and the bearing are adjusted, this simple plastic cap completes the look.
(Updated 07/11/2016 with photos and further information following a closer look at a working prototype.)