Classified releases white paper to prove Powershift hub efficiency

Drivetrain component manufacturer Classified has released a white paper with extensive details on its research and testing methodologies in an attempt to prove the efficiency of its Powershift hub.

When it was first released in 2021, the Powershift hub was accompanied by some impressive claims, most notably that it was over 99% efficient in both of its gear ratios.

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Now, through the white paper, the Belgian brand has explained how it reached these figures, including a breakdown of the methodology and the results. According to its data, the hub is 99.8% efficient in the 1:1 gear ratio, only dropping slightly to 99.2% in the 1:0.686 ratio.

The publication of the testing methodology and data comes after prominent industry engineer Hambini questioned the hub’s efficiency earlier in the year.

What is the Classified Powershift hub?

The Powershift hub emulates a traditional 2x set-up, while only using a one-chainring set-up. It achieves this through an in-built planetary gear system which offers two different gear ratios, either 1:1 or 1:0.686.

In the 1:1 ratio, the cassette rotates at the same speed as the hub shell, as is traditionally the case. The cassette then rotates faster than the hub shell in the 1:0.686 ratio, creating an easier gear that emulates riding in the small chainring – even though you’re still using a large chainring.

As this is all achieved through the rear hub, there’s no need for a front derailleur and two chainrings like in a traditional 2x set-up. That’s sure to pique the interest of aero fanatics, with the loss of the front derailleur and one chainring leading to a reduction in drag. According to Classified, there are some other major benefits too, including more instantaneous shifting which can be completed under heavy loads of up to 1,000 watts.

It also says on its website that the Powershift is “more efficient than traditional 1x or 2x drivetrains”.

To learn more about the Powershift system, check out our first-look video below.

Questions raised over efficiency figures

Upon its release, the system caused a stir and it’s since been taken up by many wheel brands, including Parcours which made it available on its Monuments range of wheels at the beginning of 2023.

It’s also made the leap into the WorldTour pro peloton at the hands of Lotto Dstny’s Victor Campenaerts during the 2023 season, making its debut at Omloop Het Nieuwsblad.

Not everyone’s been as impressed, though, with prominent industry engineer Hambini suggesting the actual efficiency figure for systems like that the Powershift uses is 96%. Meanwhile, Hambini said that the system has “a total deficit of 4% vs a 2x conventional setup in low gears (93.1% vs 97%)”.

The latter figure is important. The system is essentially designed to be a replacement for traditional 2x systems, with Classified saying on its website that the Powershift outperforms these “by far”.

Powershift methodology and data

In the white paper, Classified has explained how it arrived at its efficiency figures, providing a breakdown of its testing methodology

“Drawing on our experience in the automotive industry, we have tested the Powershift hub to the highest standards, using a test rig specifically designed to measure power loss with a maximum error of 0.1%,” Classified explains in its summary of the paper. “This allows the performance of the hub to be measured in isolation from any confounding factors, unlike tests carried out on rollers or full bike test benches.”

It goes on to explain the results, doubling down on its original figures: “The results of these tests show that the hub is 99.8% efficient in the 1:1 ratio, the same as a DT Swiss 240 hub (industry-standard) measured on the same test-rig, and 99.2% efficient in the 0.7 ratio, making Classified’s hub the most efficient internal gear hub ever tested.”

According to Classified, the hub also wins the efficiency stakes in a climbing gear too, beating a 2x set-up by as much as 1%. This, it explains, is due to friction in the drivetrain.

“Climbing on a small chainring with a 2x setup (52/36) will give you 45% more chain force than climbing on the big chainring. A higher chain force means more friction in the chain and more load on the crank and hub bearings. As a result, the losses in a 2x setup will be higher than in a drivetrain equipped with Classified.”

It’s a similar story when sprinting, where the hub proves to be 1% more efficient, according to Classified’s research. That’s on top of the aerodynamic benefit of removing the derailleur and small chainring, which Classified says results in a 1% power saving.

© Classified

Classified has tested the set-up in a wind tunnel at the Eindhoven University of Technology

For a full breakdown of the methodology and results, check out Classified’s full white paper here. The Belgian brand has handily also published a summary of the paper, here.

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