CeramicSpeed first introduced the original OSPW aftermarket derailleur cage in 2015, and alongside claims of being the fastest derailleur cage on the market, it certainly had the highest price tag of any derailleur cage on the market. The OSPW has been one of the most polarising upgrades available in the seven years since then and is perhaps about to become even more so as CeramicSpeed today unveiled its OSPW Aero system.
First spotted at the Giro and the Ironman World Championships last month, CeramicSpeed has now officially announced the OSPW Aero rear derailleur bringing an aero twist to its aftermarket derailleur cage and claiming to make the world’s fastest pully wheel system even faster.
Internal chain routing anyone?
The OSPW is a marginal gain in every sense of the phrase, with some suggesting the system built around the large pulley wheels offers just a single watt improvement in efficiency. While even CeramicSpeed’s efficiency claims put the improvements not much higher at just two to four watts. Still, a watt is a watt.
While the improved drivetrain efficiency claims associated with oversized pulley wheels are pretty widely accepted, many have questioned if such modest improvements on the original OSPW are nullified by an increase in aero drag from the larger derailleur cage. Oh and the price, many have questioned if a saving of between one and four watts was worth oh so many monies.
CeramicSpeed has moved to quash at least one of those question marks with the OSPW Aero introducing a significantly redesigned derailleur cage with a new aero profile, which certainly looks much faster. Aero-shaped oversized derailleur cages are not exactly new, with Fabian Cancellara having raced Tour de France time trials with similar setups over a decade ago. Although looking similar to Cancellara’s cage from a decade ago, CeramicSpeed’s new OSPW is the result of a collaboration with aerodynamicist Simon Smart, of Drag2Zero, Enve and F1 fame, and a two years of design process exploring multiple design iterations and wind tunnel testing.
Given that this (the derailleur cage and pulley wheels) only represents about 1% of the total system drag, we knew that we had a challenge on our hands particularly as the rear derailleur cage sits on the most complicated area of flow on the bike, and also given the position and angle changes. This is one of the most complex areas of the bike to develop.Simon Smart, founder of Drag2Zero.
The process included testing “alternative pulley layouts that enhanced aerodynamics” but ultimately were deemed too costly in terms of reduced drivetrain efficiency. The final result of the design process is a new derailleur cage that effectively wraps the existing OSPW pulley wheels and mechanically optimised design within an aero shell. Kind of like a fairing, but definitely not a fairing if the UCI ask.
CeramicSpeed and Drag2Zero’s wind tunnel testing shows that the OSPW Aero locally reduces drag by as much as 40 % on average and up to 60 % compared to a stock derailleur cage and pulleys. While that sounds like a huge saving, it’s worth considering this is 40% of the 1% a derailleur cage contributes to the rider’s overall aero drag. CeramicSpeed claims these savings translate into a pro rider saving 2.5 seconds during a 25 km time trial ridden at 50 km/h. Or in other words, not enough for Fignon to fend off Lemond, but easily enough for Serhiy Honchar to have overhauled Laurent Jalabert and avoid the agonising three-second he suffered in the 1997 World Time Trial Championships, the cloest ever finish between first and second in the event.
The savings are said to be much greater over longer distances with CeramicSpeed, suggesting a competitive age-group triathlete riding at 30 km/h will save 1:15 over a full-distance Ironman with the OSPW Aero compared to a stock derailleur.
Weight-wise, the new cage adds approximately 50 g compared to a stock derailleur cage, although, it was never intended to be a weight weenie upgrade.
CeramicSpeed has released a white paper detailing its aero testing procedure and results, however, priced at US$799 / £635 / €729 for many the marginal aero gains might not be enough to justify the oversized price tag or arguably even more questionable aesthetics.
A fairing-shaped question mark
The UCI’s regulations state “A fairing shall be defined as the use or adaptation of a component of the bicycle in such a fashion that it encloses a moving part of the bicycle such as the wheels or the chainset. Therefore it should be possible to pass a rigid card (like a credit card) between the fixed structure and the moving part.”
The OSPW Aero certainly seems to fall foul of this rule enclosing the moving pulley wheels as it does. However, the UCI has approved the OSPW Aero for use in competition. The only explanation (read loophole) we can imagine is CeramicSpeed has managed to fit a credit card lengthwise along the new cage wall and between the top and bottom pulley wheels.
Regardless of how it passes the UCI inspection and how many watts it saves, I want an OSPW Aero partly for any aero gains but mostly just because I could legally have a fairing on my bike.
Now, if manufacturers could just find a loophole for head tube and down tube fairings to enclose hoses and cables for externally routed internal cable routing wouldn’t the world be a better place?
The CeramicSpeed OSPW Aero is available now with options for compatibility for Shimano Dura-Ace and Ultegra 12speed Di2 9250/8150, Shimano Dura-Ace and Ultegra 9100/8000, and SRAM Red/Force AXS.