Royal blood? Musings on the Rotor Uno full hydraulic groupset

While steel cables comprise the control mechanisms of most bicycle shifting and braking components, the well-heeled among us have become acquainted with the reliability and freedom from maintenance of electronic shifting, as well as the power and control of hydraulic braking.

For the uninitiated, Rotor is a Spanish firm based in Madrid, best known for its cranksets and tuning-capable oval chainrings. In the past few years, they have diversified into power meters too. With pro cycling teams supposedly reluctant to swap out a drivetrain sponsor’s crankset to accommodate Rotor’s parts, the firm thought of countering this by developing their own groupset.

In a pro cycling peloton firmly entrenched in either Shimano Di2, Campagnolo EPS, or SRAM Red eTap, all robust electronic groupsets in their own right, and protected to the gills with patents, what’s a new player like Rotor to do? Enter the use of hydraulics as a control medium…and a few years later, they debuted their Uno full hydraulic groupset.


For me, in theory, embracing hydraulics for shifting was a master stroke for Rotor. Most cyclists are familiar with the pitfalls of shift cables once they start going bad and fraying, and one of the selling points of going electronic is to deliver a maintenance-free setup. With Uno, Rotor says their shifting uses a “closed” hydraulic system. Theoretically, once the 3 mm shift hoses have been cut to size for the particular bike and hooked up, there should be virtually no maintenance needed – not even bleeding. Heck, you don’t even need to look at charging batteries the way you do with electronics!

Unlike 99% of mechanical shifters, which work by incorporating an indexing ratchet mechanism in the shift levers and transfer that movement via shift cables, Rotor throws all of the indexing gubbins downstream onto the derailleurs. It’s a much more direct design, and it satisfies the mechanical nerd in me that the indexing mechanism acts so much like clockwork. The ratchets and pawls of the indexing mechanism essentially move a rack gear in and out, which then controls the actual movement of the derailleur. To get all of this to move, the hydraulics come in, but only for downshifts; upshifts are actuated by the proven method of derailleur spring tension.

The innards of the Uno control levers. Nothing to see here but master cylinder. Photo credit: BikeRumor.

The complete control lever, with brake hood. Photo credit: Rotor.

What this means, in practical terms, is that the control levers don’t contain anything inside their bodies – just the master cylinders for shifting and braking. Theoretically, Rotor is then free to make the hoods as big or as small as they can, as long as the master cylinders are accommodated.

The exposed lines on this screw equate to how many cogs you can dump per lever sweep. Here it’s set to the maximum of four. Photo credit: BikeRumor.

Actuating shifts is a variation of SRAM’s DoubleTap system. Clicking the right shift lever to its first detent performs an upshift. Pushing through that initial click detent will then perform a downshift. By turning a screw on the rear derailleur, you can set the system to dump a maximum of 4 cogs per full sweep of the right shift lever. For multiple upshifts, it’s the same as Shimano or SRAM in that the only limit is in how quickly you can push the right shift lever.

The front derailleur can work with normal round chainrings or Rotor’s oval Q-rings. Photo credit: BikeRumor.

The left shift lever still controls the front derailleur, which is shaped with a cage deep enough to handle Rotor’s oval Q-rings. While you could brute-force the lever into its full range of travel on a Shimano system to upshift into a larger cog, here Uno appears to take a more stepped approach. There are two trim positions for each chainring, which are useful when cross-chained. To facilitate a front shift up into the big ring, it seems best to go into the trim position first, before pulling a full shift. Reviews and first ride impressions I’ve seen tend to criticize Rotor here. While I’ve never ridden Uno, it appears it’s something that can be easily adapted to, given more saddle time.


Following SRAM’s lead, Uno is unique in that it offers hydraulic braking in both rim brake and disc brake forms. For this, Rotor partnered with German brake parts manufacturer Magura.

Like SRAM, Rotor offers disc brakes in the post-mount form factor. Photo credit: Rotor.

Uno uses Magura’s MT8 NXT disc brake hardware, repainted and badged to match. Like most hydraulic disc brakes, it is an “open” system to handle heat from braking loads, and following road bike conventions, it uses 160 mm rotors. Rotor offers Uno’s MT8 calipers in both post-mount and flat-mount configurations, which is a notable plus.

Again, like SRAM, Rotor offers hydraulic rim braking. Its partner Magura’s hydraulic rim brake calipers are more well-known in Europe. Photo credit: Rotor.

On the rim brake side of things, Uno uses modified RT6/8 calipers. Because there’s no need to accommodate high heat buildup, it uses a “closed” hydraulic system, much like the shifting does. Once set up, there should be little need for bleeding, although Rotor has helpful tech videos walking you through the process on its YouTube channel.

For both braking and shifting, Rotor recommends Magura’s Royal Blood mineral oil.


The relatively short cage on the Uno rear derailleur limits it to cassettes with a 30T largest cog…at least, officially speaking. Photo credit: Rotor.

Nerding out over the technology Rotor has used for the Uno groupset, frankly I’m pretty impressed. It’s a triumph of lateral thinking, and partnering with Magura is a smart move. I always admired the maintenance-free nature of Shimano Di2 and SRAM Red eTap, but was slightly turned off by the need to charge and/or replace a battery. Uno answers both.

BikeRumor’s video of the shifting close up just shows how much engineering work went into the derailleurs. That the clockwork mechanism moves a rack, that then moves the actual cage from side to side, is a thing of beauty. This also removes a lot of the limit and indexing adjustment required, since it’s all dictated by the spacing of the clockwork mechanism. All you really have to do is set the initial position correctly.

Despite the many merits of Uno, though, it’s undeniably pretty expensive. I guess there’s always the tax of being an early adopter, but the EUR2,500 price tag puts it right up there with Campagnolo Super Record EPS – and Campagnolo tends not to be cheap at any level. At that price point, is Rotor Uno as good as Super Record EPS? I can’t say from where I’m sitting.

Complicating matters is the availability of consumables, namely Magura’s brake pads and Royal Blood mineral oil.

Will hydraulic shifting be here to stay? Right now, it’s hard to tell. As a proof of concept, it is undoubtedly a success, and it certainly addresses the maintenance problem from left field. It’s been field-tested in the pro peloton, too. I think Rotor will have to work this technology down to a more accessible level, however, for it to really gain traction.

The disc brake version of the Uno groupset in its box. Photo credit: Rotor.