absoluteBLACK isn’t known for sitting back and doing things conventionally. Their oval chainrings have proven their efficiency and become one of the favorites for riders of all disciplines. Their GRAPHENlube has taken Team UAE Emirates to multiple Grand Tour victories. And now, they have a new HOLLOWcage oversized pulley system that is changing how we think about rear derailleurs pulleys and cages.
While the concept of oversized pulley systems isn’t new, the design hasn’t changed much since CeramicSpeed and other brands released their first systems years ago. The cage itself used the same concept as stock systems with two stiff plates that sandwich larger than stock pulley wheels with traditionally designed bearings. Some cages looked a little different and are more aerodynamic than a stock cage, the main benefit was efficiency from less bearing articulation and ceramic bearings.
absoluteBLACK takes a completely different approach and claims it provides better shifting, is more efficient, more aerodynamic, and quieter than other systems on the market. The HOLLOWcage uses a single plate design with vastly different bearing/pulley design. The plate is a single carbon fiber polymer plate that snakes from the outside where it mounts to the derailleur and then to the inside for the lower pulley. For the bearings, I’m going to call the three measurements the internal diameter (the inside of where the bearing mounts on it’s axle), the outer diameter (the outside where the bearing mounts into the pulley), and the thickness (the difference between those two measurements. The ceramic bearings are much larger diameters than traditional pulley bearings, but not nearly as thick. The lower bearing’s internal diameter is so large that the upper 12T pulley can fit inside.
One of the downsides of oversizes pulley systems is that they tend to have decreased shifting performance as spring tension is decreased to increase efficiency gains. Most brands then focus on making the cage stiff, but the upper guide pulley is where the stiffness matters, since the pulley is what actually moves the chain across the cassette. absoluteBLACK takes a two pronged approach for stiffness at this location. The HOLLOWcage’s 12T upper guide pulley mounts directly to the derailleur mounting bolt, putting it in the stiffest place possible in the system. Instead of an outer cage and using small hex bolts, the large internal diameter allows for using what looks more like a lockring than a traditional bolt axle. The additional stiffness comes in the bearing’s much larger size, which greatly reduces any play. In a traditional system, that play would be magnified from the small bearing outer diameter out to the outer diameter of the pulley itself. Additionally, the tooth profile is higher on the guide pulley than most brands, which helps guide the chain more precisely from one cog to the other.
For efficiency, absoluteBLACK employs a different concept than other designs. There are still the gains of using ceramic bearings and friction reduction of less chain articulation around the larger pulleys, but a major loss in efficiency comes as you start to cross-chain between the chainrings and cassette. As you get further to the opposite sides of the chain line, the lateral stress increases friction. In a major change in concept, the HOLLOWcage allows for a bit of flex to help the lower pulley align when getting to the extremes. This allows the chain to stay “straighter” and not fight against itself, leading to less friction from lateral stress.
One of the biggest gains comes through chain tension. Typically, the lower the chain tension, the better efficiency, but worse shifting performance. Due to the stiffness at the guide pulley and the taller tooth profile, the absoluteBLACK system allows you to run a lower tensions that shallower teeth and more bearing play requires. The HOLLOWcage does still provide the option to set it up at a low, medium, or high tension, depending on your application.
Aerodynamics aren’t the biggest gain for any system when it comes to overall efficiency, but it still does play a part if you subscribe to the marginal gains concept. While we don’t have any particular numbers from absoluteBLACK, they mention testing a stock Shimano Dura-Ace cage and a “market leading brand’s” cage against the HOLLOWcage system in a wind tunnel designed for smaller items. The HOLLOWcage did prove to have less drag, though the numbers between the three were fairly close, proving that at a minimum, oversized pulley cages are not a major impact on aerodynamics.
The final improvement is in sound. absoluteBLACK is using what they call a silent xring rubber suspended bands on the upper pulley. On either side of the upper pulley, they have added rubber suspended bands that hook into small guide teeth to keep them in place. As the chain makes contact with the pulley, the bands dampen the impact and reduce the sound by 12-14db over stock Dura-Ace pulleys.
The HOLLOWcage is currently only available for Shimano 9100/9150 and 8000/8050 in a 12T/18T configuration fitting up to a 32T cassette. There are plans for other current generation road groups to be released in the future, but no word on older group sets, mountain, or gravel for now. The one option you do have is what color you want for the lower pulley. From stealthy with black or titanium gray, to flashy red, gold, or their PVD rainbow, there will be options to match your style.
Now, the hard part to swallow is the price. At $699, the HOLLOWcage is definitely costly improvement to your drivetrain. When compared to CeramicSpeed though, the absoluteBLACK system is only $100 more than the Danish brand’s top of the line coated OSPW System, but half the price of the 3D printed titanium pulley OSPW system ($1400). At a claimed 71g, the HOLLOWcage weighs the same as CeramicSpeed’s aluminum OSPW System, and only about 20-30g more than the stock Dura-Ace cage and pulleys. The set comes with the HOLLOWcage, the lockring tool for the pulleys, spare ring rubber bands, and a 10ml bottle of the brand’s GRAPHENlube.
http://www.absoluteblack.cc
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