There's been a lot of history here lately. I've already written about Mavic's first electric derailleurs , and there was also a story about Shimano's pneumatically controlled Airlines groupset. Steel cables are such an obvious solution for shifting gears on a bicycle that any other idea seems at least odd. So far, the only notable exception is electric shifting, which made a resurgence after Mavic's failure. But around the same time that Japanese Di2 began its market offensive, a completely alternative idea emerged from a small company. By then, hydraulic bicycle brakes were already extremely common (in MTBs) and well-developed. Contrary to concerns from the turn of the century, they worked reliably and were resistant to falls. So the idea was obvious. Today, we have some recent history: the Acros A-GE hydraulic groupset.
How did this happen?
The Acros A-GE wasn't the first. Isolated attempts at hydraulic gear control had already been made in the 1990s, in the era of crazy CNC and bold colors. However, no one had created a complete groupset. Then, suddenly, in 2005, a certain Mr. Christoph Muthers unveiled a complete, working set called 5ROT. Light, well-made, and impressive. For the next few years, he tried to launch his own brand and production, only to finally give up and enlist the help of a larger player. Not a very large one. The German Acros is a niche brand, producing primarily high-quality headsets, bottom brackets, and hubs. So where did the idea for a drivetrain come from? More on that in the next paragraph. In any case, the collaboration was fruitful, and in 2011, the Acros A-GE was released in almost the same form as the prototype. Production was strictly limited, and the price was staggering ($2,000 or $2,306, depending on the source). So, it definitely wasn't for everyone.
Acros A-GE from the technical side
The whole groupset looks great. I'm not a fan of the most common (at least online) black and red finish, but I have to admit it's a good, classic design. At first glance, there's no doubt we're dealing with a small-scale, top-shelf product. The highlight here is, of course, the hydraulics. The system uses mineral oil in slightly thinner lines than those used in brakes. The operating principle is the same – pistons move the fluid. There are no springs (apart from the one maintaining chain tension), as each derailleur has two lines moving them in both directions. This significantly reduces weight and also allows for a clever maneuver – simply swapping the lines reverses the shifter operation. Brilliant in its simplicity! Every, and I mean every, component of the set is 100% disassemblable and serviceable (at least in theory – repairs would require spare parts). And that's not all. All moving parts are mounted on bearings – the set contains 29 bearings in total. Do you understand now why Acros A-GE is a group produced by headset and bottom bracket specialists?
What did it give?
Firstly, the lack of springs and cables, combined with lightweight materials, significantly reduced weight. The complete set (with cables) weighs approximately 430 grams. That's one-third less than the XTR of the time. Secondly, the system is sealed and temperature-resistant – it works the same regardless of conditions and mess. You can shift up and down through three gears, and the shifter movement is smooth and requires the same force throughout. Furthermore, the set supports 8-, 9-, and 10-speed cassettes, depending on the setting of the indexing element located in the derailleur.
How does it work?
Most reviewers agree that it's excellent. The hydraulics and bearings at every step ensure very smooth and fluid operation. The way the shifters work is interesting. Pushing forward shifts one direction, but to shift the other (remember, you can swap the cables to reverse the action) requires... pushing forward, but at the bottom of the paddle-shaped lever, which rotates it slightly and opens the second valve. The fact that this mechanism works as it should is quite impressive.
Acros A-GE 1x11
In 2015, a refreshed version was unveiled in a 1x11 configuration (there had also been a 2x10 setup in the meantime). The set weighed a mere 288 grams. The current-generation XTR derailleur alone weighs 252 grams. However, there was a significant drawback in this case – the largest 42t sprocket isn't strong enough for this drivetrain. The set cost €849 – I think that's quite good, and certainly much better than the first incarnation. Still, at this stage, someone must have realized that compared to its electric rivals, it was simply inferior and more troublesome to service. And that's probably why production was quickly discontinued – finding photos of a bike with the Acros A-GE 1x11 set installed is difficult. Its predecessors are also extremely rare. Currently, only the front derailleur-cable-controller set is available for a mere 1500 PLN on Amazon.
Does Acros A-GE have worthy successors?
The idea of hydraulic derailleurs hasn't died. In 2016, the well-known and popular Rotor decided to release its own variation on the theme. The UNO road groupset looked original, cost a fortune, and performed quite well, so you could say it continued the tradition of its predecessor. However, reviews were mixed. Praise was primarily given to its maintenance-free and weather-resistant nature. This is due to the fact that, like the Acros A-GE, Rotor's hydraulic groupsets utilize an indexing system integrated into the derailleurs, and of course, the hydraulics themselves. This, however, poses a problem. While technically simpler and less reliable than indexed shifters, it does make it (especially when combined with the smooth operation of hydraulics) quite difficult to tell how many gears you've shifted and where the shift point is. The front derailleur was also reported to be less than smooth. It's worth noting that a version with hydraulic rim brakes was also available—a choice for the hipsters. Both these and the disc versions are the result of a collaboration with Magura.
Rotor 1x13
Rotor didn't listen to the feedback and... got rid of the front derailleur. In 2019, they introduced a groupset simply called Rotor 1x13. Available in several versions, both road and MTB, it can include wheels (with a dedicated freehub), cassette, crankset (also with power meter), and chain. It also works with 12-speed cassettes. The entire unit is very light (though not the lightest on the market). Reviews unanimously agree that the issue with mediocre feel remains, but the build quality and range are key factors. Price? €1,750 to €4,490, with the latter price being the top-of-the-line version with power meter and carbon wheels.
I don't think hydraulic shifting will ever reach a wider audience, unlike electric shifting, which has a chance. Still, it's always encouraging when someone creates a working solution that's different from the biggest players on the market. And there's certainly no shortage of wealthy geeks who value originality above all else. And that's good! Maybe someone will decide to install one on our gravel bike ?
The photos are from the Acros A-GE group manual unless otherwise stated.
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