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Road Gear

Specialized uses novel test protocol for S-Works Carbon Dual power meter

Working with the University of Colorado’s Human Performance Lab, Specialized creates new power meter testing protocol.

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BOULDER, Colorado (VN) — In a laboratory filled with custom-made treadmills, discarded research equipment, and a wide array of bike parts new and old, a power meter was born.

Perhaps that’s oversimplifying a bit, but the University of Colorado’s Human Performance Lab, inside an old building on the Boulder campus, is where Dr. Rodger Kram’s team tested the S-Works Carbon Dual power meter. Specialized claims it is the lightest, most accurate power meter on the market. The first boast is easy to check on any old scale. The 4iiii power pods integrated on both sides, add just 30 grams to the carbon S-Works cranks.

The second superlative required Kram’s lab.

A few years ago, Kram and his team were working with Specialized to determine if the Futureshock head tube suspension — then in development for the new Roubaix — cost any efficiency to the rider. They had a subject ride a variety of efforts on the bike, checking output with a Quarq power meter crank. And it was all done in that lab, on an enormous, custom-made treadmill, originally meant for cross-country skiers.

They determined that the suspension didn’t detract from the bike’s performance. This was, however, the unintended beginning of a new experiment.

Every power meter is marketed with a specific claim of accuracy, such as +/-1 percent. They are ordinarily tested two ways: with a static weight and a dynamometer. The first test applies a known force to the power meter to confirm that its strain gauge measures true. The second applies torque to the meter at varying RPM, which also tests the cadence sensor.

That wasn’t good enough for Kram and Specialized, however. They felt that the battery of conventional tests failed to truly verify accuracy. They wanted a way to test a power meter when variables like cross-chaining, wide temperature swings, and different pedal axles were thrown into the mix. (It’s worth noting that some power meter manufacturers do account for different chain angles and gear combinations, using a dynamometer.)

Specialized Power
It may not look like much, but this huge treadmill in the University of Colorado’s Human Performance Lab is where a team of researchers developed a new protocol to test the accuracy of power meters, specifically the new Specialized Power Crank. Photo: Spencer Powlison |

So, the CU research team went back to that giant treadmill and started to work on a protocol to calculate power to verify the number shown on a Garmin screen. They could be sure of the treadmill belt’s speed. They could also control the rider’s weight, weighing them before and after riding and limiting water intake. The scientists worked out ways to calculate rolling resistance, using a counterweight of lead BBs and even monitored the treadmill belt heat as the experiments progressed.

Along the way, they also subjected the power meter prototypes to extreme heat and cold. After calibrating the meter in either freezing cold or 50-degree Centigrade heat, they’d rush to mount it on a bike for testing on the treadmill.

In the end, Boulder lab ended up with a testing protocol that was good enough to be presented at the Rocky Mountain regional conference of the American Society of Biomechanics. They are also planning to publish a full paper in the Journal of Applied Biomechanics.

And Specialized ended up with a new power crankset that it believes is more accurate and consistent than the competition.

According to these tests in the Boulder lab, the cranks are accurate within 1.5 percent. Specialized terms this “real world accuracy.” The power meter requires CR2032 batteries and communicates with Ant+ or Bluetooth.

All of the new S-Works Tarmac SL6 disc bikes will come with the S-Works Carbon Dual power meter. The power meter will also be available aftermarket in fall 2018 for $1,150. Or, if you prefer a Dura-Ace crank, Specialized will offer one with the same power meters for $1,500. A single-sided S-Works crank upgrade will be sold for $750 — like most one-sided options, that will simply double your left-crank power data for an estimated total power figure. Specialized also plans to sell one-sided 105 and Ultegra power meter cranks at $425 and $525 apiece.