HOLLOWcage® for Shimano 9100 / 8000. Our revolutionary mono-plate OSPW design is the quietest, best shifting, aerodynamic derailleur cage design created to date. It is a dawn of new era for rear derailleurs. HOLLOWcage ® OSPW has a carbon-polymer mono-plate construction with bespoke, oversized, full ceramic bearings and the most advanced silencing pulleys ever created.

Why is our Hollowcage so special?

• It is super silent (over 12dB noise reduction vs stock)
• The shifting is as good as with the original Dura Ace cage
• It’s more aero than the OEM cage and other oversized cages
• It saves more watts than other cages
• One of the lightest oversized cages on the market
• First mono plate construction of its kind

The new era of silent pulleys. Meet the silent Xring Pulley™

Does it bother you when you ride in a really quiet scenery but you can still hear your bike’s chain engaging the pulleys? This familiar clunking noise has been accompanying us on every ride for decades. It’s time for a change.

Common polymer pulleys are fairly loud, this has always been a norm. Aluminium pulleys are even worse as the material radiates the sound more than any polymer, making them louder. We are introducing a completely new generation of pulleys, which are able to reduce the sound level by 12-14dB when compared to stock Dura Ace pulleys. This corresponds to roughly 60% of the noise reduction. Practically speaking, the cage becomes very silent.

We use a patent pending solution, our special xring rubber suspended bands, that dampen the chain impact on the guide pulley teeth, therefore eliminating the engagement noise, which is the single biggest contributor to overall drivetrain noise. From now on, your ride is going to be more silent than it used to be and you will hear sounds that you haven’t noticed before. It's the new era of derailleur cages.

Flexible cage is better than a stiff one.

Contrary to common knowledge, flexibility is good as it allows the cage (and therefore lower pulley) align better with the angle of the chain when using the higher gears of the cassette. This means less friction (and less Watts lost) as the pulley doesn’t have to fight against the chain itself. Shimano has partially solved this issue by bending the lower part of the cage slightly outwards, to align better with the chain when using top of the cassette range. We have taken a different approach and eliminated one part of the cage all together, creating mono plate cage that can dynamically adapt to the chain angle.

Stiffer guide pulley, not cage, means better shifting.

Many companies try to convey that a stiffer cage is a better shifting cage. But the single most important factor that impacts the shifting is the upper pulley itself. Since the upper pulley is mounted directly to the rotating pivot axle, the flexibility of the cage plays very little role. It’s the upper pulley that moves the chain left and right enabling gear change, so making the upper pulley really stiff allows for greater shifting precision. Most oversized pulley cage systems use very small bearings, with a lot of lateral play at the teeth which in turn provide poor, sloppy shifting. HOLLOWcage®, unlike other pulley cage systems, use abnormally large, bespoke, full ceramic bearings that make the pulleys incredibly stiff. Lower bearing alone is actually big enough to fit 11T pulley inside of it.

The problem of shallow teeth.

One of the main shifting issues, apart from pulley stiffness alone, stems directly from the low teeth profiles. Low teeth simply can’t move the chain effectively left or right when you change gear. They are the only points of contact with the chain, but for some bizarre reason, majority of oversized pulley systems come with very shallow teeth profiles. This is the major contributing factor to oversized pulley cages shifting badly. HOLLOWcage® uses very tall teeth of the upper pulley which gives the best possible shifting precision.

Oversized cage is actually more aero.

There is a general belief among some of the riders that oversized cages are less aerodynamic. Their larger surface area, when compared to OEM cages, must result in some power losses, which would offset the gains generated by the bigger pulleys. We have tested the market leading cage as well as original Dura-Ace cage in a bespoke wind tunnel, designed for smaller objects. HOLLOWcage® proved to be more aerodynamic than the OEM (DA cage) as well as the other leading brand. However, the absolute difference is relatively small, proving that a bigger cage will not set you back and cause any meaningful Watt losses, no matter which cage you use.

The game of watt saving.

There are four main components to the savings that oversized pulley system can provide. Bearing quality and its lubrication, the number of teeth in the pulleys, the cage spring tension and the ability of the lower part of the cage to align with the chain. We are using bespoke, shielded, oversized full ceramic bearings that are actually lightly greased not oiled (nor dry). The difference between special grease and oil is only 0.01W in real life conditions, under load, despite the fact that one pulley can free spin and another not at all with no load present. What we gain is great durability and reliability at a cost of 0.01W. Bearings, contrary to common assumption, are not the place of big savings (0.03-0.1W between a high-quality bearings). It’s the companies that sell them want you to think they are by comparing them to Acera level pulleys.

While most of the oversized pulley systems have very similar pulley sizes, the biggest savings mostly come down to the spring tension and the ability of the cage to adapt to the chainline. There is a linear correlation between spring tension and the power losses generated by the cage. Shallow pulley teeth paradoxically require higher spring tension to maintain reasonable shifting quality.

HOLLOWcage® is using lower spring tension than any other cage on the market, while still providing excellent shifting thanks to the unique combination of pulley stiffness and tall teeth profiles. In addition, it is the only cage that can dynamically adapt to the variable chainline, minimizing friction at the lower pulley.

Our bearings are full ceramic. In technical nomenclature, it is a bearing with inner and outer race as well as balls, made of ceramic material. The seals and the cage however, are made of polymer. Other common types of bearings are steel bearings and hybrid bearings. The latter is often mistakenly called "ceramic" bearing but only the balls are ceramic, races are still made of steel. Hence there is a term "full ceramic" indicating that not only the balls are made of ceramic but both races too. Our bearing races are made out of 100% Zirconia Oxide ceramic and balls are made of Silicon Nitride ceramic. The cage and seals are of course made of low friction polymer.

How to mount Hollowcage

You should mount the cage with the lowest spring tension setting (First hole from left). If you use 11-32T cassette in combination with 52/36T chainrings or bigger you may need to set the cage with middle spring tension setting (middle hole) to account for the chain growth, but only if first position produces loose chain in small - small gear.

• Size (Mass +/-1g):  71g (12T/18T)
• Color: Lower lockring: PVD Rainbow, Black, Titanium, Red, Gold
• Compatibility: Shimano Dura Ace 9100 / 9150 / 9170 , Ultegra 8000 / 8050. Fits up to 32T cassette. NOT compatible with Ultegra long GS cage derailleurs.
• Material: Carbon fiber-polymer matrix, 7075 Aluminium, rubber, ceramics
• In the box: Complete cage, lockring tool, 2x spare xring rubbers.