Test: After several years of development work, the Spanish supplier Rotor presents the world's first hydraulic racing bike shift system, the Rotor Uno. Velomotion has found out whether the new system can keep up with the current mechanical and electronic shifting systems.
Rotor Uno: Can bicycle gears be reinvented?
On mountain bikes and city bikes, fixed gears and even infinitely variable hub gears indicate that there is still room for innovative developments. With racing bikes, however, things are different: so far it seems as if there will be no alternative to derailleur gears in the long term. If you want to get involved in the market, you have to modify the proven technology in an individual way without deviating too far from the existing standard.
But this is exactly where the problem lies: With every new development, the scope has become smaller, especially in terms of patent law. And to develop a completely new shifting mechanism that still meets the functional and ergonomic requirements of road cycling is hardly possible.
Rotor Uno: five different groupsets on the road bike market
And that's one of the reasons why the manufacturer Rotor didn't bother with mechanical solutions for long, but instead aimed for a hydraulic circuit with the Rotor Uno, which is now available on the market. As a reminder: Rotor started with Q-Rings, the asymmetrical chainrings, added lightweight aluminum cranks to its range and then launched its own power meter, InPower, along with accessories such as the frequently installed chain catcher. So now a circuit that would make the Spaniards the number five complete groupset supplier after Shimano, Campagnolo, SRAM and FSA - but their system is quite unique.
In principle, the shifter works like a hydraulic pump that puts pressure on the system and thus pushes the rear derailleur inwards. If the pressure is reduced again, a spring pulls the derailleur back outwards. A mechanism that is integrated in the rear derailleur or front derailleur ensures the necessary locking. In the case of the rear derailleur, the ratchet is even visible: it is a fine toothed rack below the drum at the rear of the rear derailleur.
To adjust the rear derailleur, you turn a small Allen screw that changes the position of the rack. As a result, the rear derailleur moves further inwards or outwards when changing gears. This adjustment has no effect on the hydraulics. It's like an endless loop; it is therefore basically impossible for the circuit to misalign. Because the lever and rear derailleur are not mechanically connected, you can push the rear derailleur inwards by hand onto any sprocket, where it then stops.
From there you can then continue to switch in both directions as usual. A lever on the hydraulic drum decouples the rear derailleur from the rack so that it moves outwards onto the smallest sprocket. This is very practical when changing wheels - you don't have to laboriously switch to the final sprocket and as soon as the new wheel is in, you can push the rear derailleur into the optimal gear for starting off as described (although you have to turn the cranks, of course).
The Uno lacks an inward and outward limit stop; You can't switch over the range specified by the grid anyway. You can set the number of switching steps in block from "difficult" to "easy" - at least one, maximum four.
Rotor Uno: hydraulic rim brakes from Magura
The look of the Rotor Uno also differs greatly from what you are used to. The filigree rear derailleur looks almost classic with the curves of the swing arm; the hydraulic rim brakes contributed by Magura have a technical industrial look. The black and red KMC chain is an eye-catcher. The hydraulic drum on the front derailleur is hardly noticeable in the age of electronic shifting - it is about the same size as a Di2 servomotor or eTap battery.
The hydraulic lines of the gearshift are noticeably slim - significantly thinner than a typical brake line. They can be bent into tight radii; they should be made for aerodynamically optimized installation. The handles, which are available in two sizes, seem quite large and a bit coarse, especially since their inner workings should actually be quite reduced. Overall, however, they feel good in the hand; the long brake lever comes comfortably close to the handlebar arch and is easily accessible from the lower link.
And that brings us to the essential point of the Rotor Uno – its functionality. The shifting principle is similar to that of SRAM's DoubleTap levers: a short press causes the rear derailleur to fall outwards, if you press the lever further inwards, the chain changes to the larger sprockets. However, the switching feel differs significantly from what you are used to, due to the completely different function. With the mechanical lever, you actuate the ratchet mechanism in the lever directly, the gearshift is attached to the back, so to speak. With the Rotor Uno, on the other hand, it's the other way around: you apply pressure to a hydraulic system, the movement of which only causes the shifting mechanism to engage backwards/downwards. For this reason, the switching steps in the hydraulic system are less defined; the Rotor Uno does not engage as clearly as something the SRAM system with the same operating logic. Overall, the Spanish circuit feels softer, but you get used to it quite quickly.
Rotor Uno: slightly larger operating forces required
However, in a direct comparison with a current mechanical system, the SRAM Force 1, it becomes clear that the hydraulic circuit works with noticeably longer lever travel. This is particularly noticeable when you switch to the larger sprockets. In this context, the switching step limitation already mentioned comes into play again. The fact that you accidentally shift two gears at once in the "easy" direction is actually impossible due to the large lever swing required; this special function can therefore be neglected and the screw set to "maximum number of switching steps".
What is also striking about the shifting behavior is that the Rotor Uno requires somewhat greater operating forces. As far as handling is concerned, the hydraulic system falls behind current mechanical gearshifts, not to mention electronic systems: their advantage lies precisely in the fact that they simplify the shifting process by pressing a button instead of levering it. The shifting process itself works satisfactorily: the chain slides cleanly onto the smaller sprocket of the super-light cassette and threads itself smoothly onto the larger one.
The large lever travel is also noticeable when operating the front derailleur. Two trim levels are offered, which you also need, because if several sprockets are shifted at the rear, you have to readjust the front to avoid grinding noises. The clearly asymmetrical chainrings are not necessarily conducive to the shifting process, but they feel extremely comfortable - it doesn't seem necessary to get used to them, the pedaling seems much lighter with them.
Rotor Uno: Disc and rim brakes are compatible
On the test bike, the hydraulic circuit is combined with hydraulic Magura rim brakes, which build up high braking forces with good controllability. However, the DT Swiss carbon rims did not break any records in conjunction with quickly wearing Swissstop pads. By turning the cylinder at the front of the brake, it can be opened to change the wheel. It is interesting that the Uno levers harmonize with both rim brakes and disc brakes. The group can therefore continue to be used when changing to a disc brake frame.
For our test, Rotor mounted the Uno on an aerodynamically optimized Cervélo S5 with aero wheels and high-quality Enve components - a bike that feels fast from the first meter, shines with high rigidity with rapid acceleration and is not even uncomfortable, despite Aero fork and post. Equipped with a rotor power meter, it is ready to race and weighs seven kilos including the pedals - no wonder given the super-light group. However, the bike costs around 10.000 euros. The UN group contributes almost 2.500 euros; for this sum you get gears, brakes, cassette and chain, but no crankset - for the Rotor including chainrings you have to pay at least 350 euros again. In terms of price, the Rotor Uno is therefore higher than the new Dura-Ace Di2 with rim brakes.
Rotor Uno: Handmade in Spain
Of course, this also has to do with the fact that the group is made in Spain, not in Taiwan or Malaysia, but the high price spoils the joy of this very innovative product. Because in the end, the Rotor Uno can only score points by showing a third way when it comes to derailleur gears; when it comes to function, it is at a disadvantage. It should still find friends - it can hardly get any more exclusive than the hydraulic shifting system.
