Rotor Uno long-term groupset review: Different strokes

by James Huang

Every road derailleur on the market today is based on either a network of braided steel cables and housings, or some combination of electric batteries and motors. Both concepts are very well-understood at this point, highly refined, relatively easy to maintain, and readily accessible in terms of both cost and availability.

The Rotor Uno groupset, however, is not like those other designs.

Instead, it uses a fully hydraulic system for both the derailleurs and brakes. There are no cables or housings to replace, and no batteries to charge. It’s competitively lightweight, impressively adjustable, and undeniably exclusive.

But has Rotor created something that can actually motivate people to choose Uno over what’s already out there, or does its appeal mostly lie in its novelty? According to CyclingTips global technical editor James Huang, it’s good to be different. But it’s better to just be better.

It’s all business inside the two-piece plastic clamshell that forms each Rotor Uno lever body.

Story Highlights

  • Key features: A fully hydraulic road groupset available in both rim-brake and disc-brake variants
  • Weight: 2,304g (rim-brake groupset, complete)
  • Price: US$2,700 / AU$TBD / £2,400 / €2,500
  • Highs: Truly innovative design, unique aesthetic, weather sealed hydraulic mechanism, no batteries to charge
  • Lows: Vague and clunky shift performance, poor stopping power with the rim-brake option, extremely tedious installation process, very expensive

Why hydraulic

Modern cable-actuated drivetrains are incredibly evolved, and despite their relative youth, battery-powered electronic ones have already surpassed even the best mechanical transmissions when it comes to pure performance. While it’s easy to harp on minutiae, the fact of the matter is that all of the groupset offerings these days — from budget to flagship, and from Shimano, SRAM, and Campagnolo — arguably border on functional perfection.

So why bother with developing a fully hydraulic system, particularly given the engineering challenges presented to a company of Rotor’s comparatively minuscule size?

Hydraulic pressure is used to move the derailleur inward, while the coil spring pulls it back out when that pressure is released. The ratcheting mechanism is partially exposed, which means the Rotor Uno groupset is most certainly not cyclocross-friendly.

According to Rotor, the Uno’s hydraulic design is fully sealed from end-to-end, meaning there’s essentially zero chance of contamination and almost no maintenance involved. Since the derailleurs are still human-powered, you never have to worry about heading out with a dead or nearly-dead battery, it’s fairly easy to diagnose a mechanical issue (at least compared to an electronic drivetrain), and although you might think an oil-based system would require a lot of extra hardware, Uno is pretty light.

Claimed weight for a complete SRAM Red eTap rim-brake groupset is 2,043g, for example, including a BB/PF30 compact crankset and press-fit bottom bracket, 11-28T cassette, chain, and all requisite batteries, cables, and housings.

Claimed weight for a complete Shimano Dura-Ace Di2 R9150 rim-brake groupset is 2,022g for a similar configuration, plus a bit extra for the wiring harness and brake cables and housing.

But the Rotor Uno? Actual weight for the complete rim-brake setup I tested is 2,304g, all-in. That figure may seem a little disappointing at first, but keep in mind that Rotor’s Aldhu crankset isn’t a featherweight at 626g, nor is the matching aluminum bottom bracket at 105g. Swapping both of those could easily save over 100g, and given the chunkiness of the hydraulic rim-brake calipers, the gap also narrows considerably when you look at the disc-brake versions.

As with the rest of the groupset, the Rotor Uno front derailleur is made mostly of CNC-machined aluminum.

In fact, based on claimed weights, a disc-brake Uno groupset is quite a bit lighter than a comparable Dura-Ace Di2 package, and nearly identical to SRAM Red eTap.

Retail price for the complete Uno groupset (with Aldhu crankset, and in rim-brake or disc-brake configuration) is US$2,700 / £2,400 / €2,500. Australian pricing is TBC.

Planning on a DIY installation? Better set some time aside

Before I get into how Uno performs on the road, let’s first talk about what it’s like to install the groupset. Rotor has typically only provided complete test bikes to editors, but I was insistent on building this one up myself. In hindsight, I wish I had taken Rotor up on the offer.

Rotor sells the Uno groupset as a complete kit, with all of the hydraulic lines already connected and the system pre-bled. However, those lines still have to be cut to length, and given trends in modern bike construction, those lines also have to be internally routed through the frame, as I had to do on my Cervelo R3 loaner.

The Cervelo R3 is an outstanding chassis on its own, but in this case, it’s also one of very few on the market that will accept the Uno rear rim brake’s full-length hydraulic hose.

As a result, installing Uno requires you to cut, route, re-connect, and then re-bleed four separate hydraulic lines. Rotor has at least sized the diameter of the lines so as to work with Shimano Di2-compatible frame ports, but if you opt for the rim-brake variant — as I did here — you’ll also have to make sure the frame is equipped to handle full-length rear brake housing.

Adding further tedium to the process is the fact that each lever body has to be partially disassembled to access the hydraulic fittings.

Unlike Shimano and SRAM hydraulic levers, both of which conveniently place the connections on the outside of the body, Rotor hides everything away inside each Uno lever’s two-piece plastic clamshell (imagine Arnold Schwarzenegger peeling the flesh off of his forearm in Terminator 2).

Each body is held together with eight tiny screws.

The bleed process itself is quite straightforward, though, and Rotor clearly benefits from its development partnership with long-time hydraulic veteran Magura. The procedure will be familiar to anyone that has ever bled a hydraulic disc brake: Fill the syringes, connect them to the ports, open the ports in prescribed orders, push fluid through the system until all the air has been evacuated, and then close everything off. Uno uses the same mineral oil formula as Magura does on its disc brakes, too, meaning it won’t irritate your skin like DOT fluid, it won’t eat paint, and it should be relatively easy to source when needed.

Once the lines are installed and bled, the rest of the fine-tuning goes quickly, thanks in no small part to Rotor’s detailed tutorial videos. Chain gap for the rear derailleur is directly coded to cassette size so there’s no guesswork there, and etched guidelines on the front derailleur cage make it easy to get the position just right.

Similar to how Shimano allows some level of customization in terms of how its Di2 system shifts, Rotor has also built some tunability into Uno. Users can choose how many downshifts you can execute per lever push, for example, and neat inline adjusters allow you to fine-tune the lever effort as well.

The hydraulic shift lines are just slightly larger than Shimano Di2 wires, so they can use the same routing ports.

Straightforward the process may be, but it still amounts to a lot of steps. I can typically build up a bare frame with a mechanical groupset from start to finish in about an hour, but the Rotor Uno installation took me nearly an entire day. On the upside, though, it’s a one-and-done affair. I spent several months on my Uno loaner groupset and never had to do a thing, and Rotor only recommends flushing and re-bleeding the system annually.

Light on the scale, heavy on feel

Visually, Uno is unlike any other road groupset on the market. Whereas Shimano, SRAM, Campagnolo, and FSA all resort to more organic-looking aluminum forgings and molded carbon fiber parts, the vast majority of the Uno bits are CNC-machined (in Madrid), and so they have a distinctly industrial look to them, all sharp edges and hard lines.

The rear derailleur works reasonably well, but shifts still aren’t as smooth or quiet as the competition.

One might rightfully question why Rotor has gone this route given that machining is a far more expensive manufacturing process on a per-piece basis. But again, Rotor is a comparatively tiny company, and processes like forging and casting require a lot of initial investment that only makes sense when amortized over a large production volume. Rotor understands CNC-machining very well, though, and given Uno’s more small-batch production, the approach makes sense — and it also lends the groupset a very distinctive aesthetic that is truly unlike anything else out there.

However, the way it feels is very different, too, and that’s not necessarily a good thing.

Rotor follows SRAM’s lead in that each Uno lever is equipped with a single shift paddle. Just like DoubleTap, pushing the Uno shift lever a little bit yields a single upshift. If you push past that point to the next click, the system releases hydraulic pressure and a steel spring pulls the derailleur back in the other direction to give you a downshift. And again, just like SRAM, if you push further still, you can get multiple downshifts — up to four, depending on how you’ve set up the system.

See those little lines on that stainless steel screw? That’s how many downshifts you can get from a single lever swing. It’s quite neat that you can customize that, and even neater still that it’s a mechanic adjustment, not something you program on an app or computer.

Rotor’s use of hydraulics obviously sets it apart from SRAM’s mechanical groupsets already, but there’s another key difference: Whereas every cable-actuated transmission locates the indexing mechanism in the levers, Uno places them in the derailleurs.

In concept, it makes a lot of sense to locate the indexing function as close to where the movement is happening as possible. But in practice, it yields a vague action that is disappointingly lacking in both tactile and audible feedback. The shifts happen as they’re supposed to, but the process feels distant and abstract — the polar opposite of what SRAM’s DoubleTap provides, and with even less of a connected feeling than what you get with Shimano’s “Light Action” philosophy.

You get used to it eventually, but even then, you learn how far you have to move the shift paddles to get the number of gear changes you want based on muscle memory, not by feel or sound.

Surprise! The shift paddles are made of CNC-machined aluminum. As you’d expect, they feel reassuringly solid and stiff.

There’s also more effort required than usual to move each shift lever (even with the inline hydraulic adjusters backed all the way off), and the lever throws are uncomfortably long, even for my large-sized hands. And despite being a hydraulic system, the motions don’t feel as low-friction and fluid as you might expect.

I could more easily overlook all of this if the way Uno moved the chain around was truly world-class, but it falls short in that respect as well.

The machined steel-and-aluminum cassette is a piece of engineering art, and extremely lightweight to boot. But even with the recommended KMC chain, rear shifts are louder and rougher than I would expect from something of this caliber (and cost). The chain ends up where it’s supposed to, but it does so in a somewhat clunky manner that does’t match Uno’s premium price.

The Rotor Uno cassette is a really neat piece of kit. The first nine sprockets are machined from a single hunk of steel – not unlike what SRAM does with Red – and the last two are machined from aluminum. It’s stupendously light at just 133g in a 11-28T size.

Front shifts are particularly disappointing.

As with the rest of the Uno components, the front derailleur cage is made of machined aluminum. That isn’t an issue in and of itself, but the shaping isn’t particularly refined, and the derailleur body lacks the additional bracing against the seat tube that Shimano and SRAM have added to their units in recent years for extra rigidity.

Moving the chain to the outer chainring requires a firm push on the lever, and despite plenty of experimentation in terms of front derailleur positioning (keen-eyed readers will note that the derailleur is positioned fairly high in the photos), the chain still hesitates if you’re trying to make a shift under heavy load.

Making matters worse up front is the fact that there are four distinct trim positions, but no multi-click feature built into the front derailleur like there is for the rear one. As a result, dropping down to the inner chainring sometimes requires multiple lever pushes to get things silent. That in and of itself is a fairly minor nuisance, but it’s yet another sign that the shift performance just isn’t where it should be.

So-so ergonomics

Even the way the Uno levers feel in your hands leaves room for improvement.

The lever bodies are big and chunky, with a cross-section akin to a rounded-off and subtly tapering rectangle. The broad upper surface admittedly spreads out the load to minimize pressure points, but the shape still feels more industrial than organic.

The Rotor Uno levers look quite flashy with their carbon fiber blades and eye-catching graphics. But the body shape doesn’t feel very refined, and the hoods have an unnerving tendency to squirm around.

The lever bodies’ thin-walled, two-piece clamshell construction also seems less solid than the molded one-piece plastic bodies used by other brands, the rubber hoods look a bit unfinished, and they don’t fit nearly as snugly as I’d prefer, either. Especially when wet, they tend to squirm around a little on the bodies.

On the plus side, the lever reach is adjustable to make the controls easier to access, and the brake lever is long enough that you can easily find it with an extended fingertip when you’re careening down a mountain pass in the drops. I found the shift paddles to be too smooth and slippery, though, which only further highlights the long throws required. Some additional texture would be greatly appreciated here.

High hopes for the hydraulic rim-brake option, dashed

I’ll readily admit to being an ardent fan of hydraulic disc brakes, but even so, I’m not going to ignore recent advances in rim-brake technology that have narrowed the gap in stopping performance. To that end, I made the decision to go with the hydraulic rim-brake variant of Rotor’s groundbreaking Uno groupset to see just how good it might be. After all, a hydraulic rim-brake caliper potentially offers enough power to literally crush a rim, and SRAM has already demonstrated that the technology can be utilized to great effect with the hydraulic rim-brake version of its Red 22 groupset.

The problem with the Rotor Uno rim-brake calipers, however, is that the caliper design hasn’t been updated from what Magura designed for the 2012 Cervelo P5 triathlon bike, and it doesn’t seem like the hydraulic ratios are matched as well to the more modern Uno levers as they should be.

I had high hopes for the Rotor Uno hydraulic rim brakes, but alas, they were not to be. The idea still holds a lot of merit in my view, but the calipers desperately need a redesign if order to realize their potential.

On the road, the lever action is heavy, slow, and dull, and although the power is quite controllable, there’s nowhere near as much of it as there should be. The contact point isn’t very distinct, either, and the calipers themselves are clumsy-looking and heavy. The integrated quick-release function doubles as a pad wear adjuster, but even that is disappointing in that the adjustment increments are too coarse.

Given the calipers’ age, it should perhaps also come as no surprise that they’re not ideally suited to the wider rims that are more commonly used these days. I ended up having to swap to lower-profile pad holders to suit the Knight Composites TLA tubeless-compatible carbon clinchers I started with (which seem very good, by the way). And then even with the aggressive texture of the HED Jet 4 Black aluminum-carbon hybrid aero clinchers I switched to later for comparison, I found myself constantly wishing I was on a conventional cable-actuated dual-pivot calipers, desperately in search of more power.

Switching to a stronger return spring in the calipers would likely help with the snappiness, as would perhaps lower-friction seals. Likewise, new aluminum arms would instantly make the brakes more compatible with wider rims and tires. However, given the direction things are headed in the market, I don’t expect that any of those things will actually happen.

A hydraulic cylinder pushes a wedge upward when you pull the brake lever, which then pushes the tops of the brake arms outward.

To Rotor’s credit, the disc-brake version of the Rotor Uno groupset is much more in keeping with modern competition. While I’ve only dabbled a bit with that setup, it seems to perform much more like what you’d expect, with a light and positive feel, ample power and control, and a snappy lever return (not to mention a more competitive weight).

If you’re at all considering a Rotor Uno groupset, I strongly recommend you go that route; the rim-brake calipers just aren’t worthwhile.

The spinny bits

Rotor provided a complete groupset for this review, including its new Aldhu crankset and a complete 35mm-deep Knight Composites TLA tubeless carbon clincher wheelset laced to Rotor’s new Rvolver hubs.

Like the rest of the Uno groupset, the Aldhu crank eschews composite construction for CNC-machined aluminum. The rectangular-profile arms are big and notably stout — and drilled lengthwise to save weight — and joining the two is a wide-format, 30mm-diameter machined aluminum spindle that works with nearly every frame design on the market (with Trek’s BB90 being the one main exception). A separate spindle is offered for disc-brake bikes with 142mm-wide thru-axle rear hubs to maintain a proper chainline, too.

Rotor’s new Aldhu crankset is a neat piece of engineering. The modular spider isn’t a new idea, nor is the one-piece double chainring. But it’s how that’s all attached to the crankarm that’s truly clever.

The modular design features a separate spider so that riders can choose from a range of gearing options, including 1x and 2x, and both fully integrated versions and more conventional ones that use separate chainrings. Double-chainring options only cover traditional road sizes, although others could certainly be added later.

Rotor has always been one to push the envelope of ingenuity, and that tendency shows through in how the spider is attached to the arm.

Instead of just bolting the spider to the arm as is usually the case — or using a spline pattern and a separate lockring — Rotor uses the 30mm-diameter spindle itself to hold everything together. As the main bolt pulls the splined spindle into the socket on the arm, a shoulder on the spindle simultaneously sandwiches the spider in between the two. It’s an extremely elegant solution and it worked well during testing with no creaking or notable flex.

For this particular setup, Rotor also provided its new one-piece double-chainring setup, which is machined from a single hunk of aluminum. The four-arm spider is extremely rigid on its own, and the milled-in ribs on the back of the outer chainring only add to the stiffness. As usual, there’s also an array of machined-in ramps and stainless steel pins to help lift the chain on to the outer chainring.

Normally, cranksets with modular spiders have some means by which the spider is attached to the arm, and then that sub-assembly is secured to the axle. The Rotor Aldhu, however, skips that intermediate step and sandwiches the spider in between the crankarm and a shoulder on the spindle as those two parts are pulled together with the crank bolt. It’s an ingeniously elegant design, but also one that requires very stringent tolerances to work properly.

Unfortunately for Rotor, much of that is squandered by the Uno front derailleur design; when I used the Aldhu on a different bike with a more conventional transmission, it actually shifted quite well.

Overall, I was impressed with the Aldhu crankset, and it certainly presents a viable alternative to the big brands, especially if you want something a little different.

The hubs were a different story.

The Rvolver driver mechanism uses an array of cylindrical steel pawls that push outward against a steel ratchet ring. As the freehub body freewheels, the ratchet ring slides axially inside the hub shell.

Rotor uses a truly novel internal mechanism for the rear Rvolver hub, and while it functioned perfectly fine for me, it’s also obnoxiously loud when freewheeling and produces far too much drag — enough that a quick backpedal could almost derail the chain. The 14.4-degree engagement speed is reasonably quick, but the long travel of each spring-loaded, cylindrical pawl still makes for a somewhat vague take-up when you start reapplying power.

The concept still seems sound to me, but as these are currently, the hubs get a hard pass from me.

A mixed bag

I’ve now known Rotor founders Pablo Carrasco and Ignacio Estellés for over 10 years. I first met the pair at the Saunier-Duval team training camp in 2007, where the duo was pushing hard to get a high-profile team — maybe any team — to use their then-radical Q-Ring elliptical chainrings. I’ve always found them to be refreshingly genuine, appropriately ambitious, and admirably hard-working. Perhaps even more importantly, I’ve always felt that they truly believe in the merits of everything they’ve developed that proudly wears the Rotor logo, confident in what they’ve created but never with even the slightest hint of arrogance.

And so knowing how hard those two will take this, it pains me to say that this Uno groupset just feels like a miss.

The concept of a fully hydraulic groupset holds a lot of promise in my view, and for the exact reasons Rotor touts: there are no batteries to charge, there’s little-to-no maintenance required, and the hydraulic bits are totally sealed from weather. But despite years of delays, Uno is still sorely lacking in refinement, and it just doesn’t work as well as it needs to in order to be a viable alternative to the mainstream brands.

It seems like the ingredients are here, but there’s something off in the combination and preparation. Rotor announced a new 1×13 hydraulic drivetrain for both MTB and road/gravel use at this year’s Eurobike show, for example, and I’m cautiously optimistic that Rotor has been able to incorporate meaningful improvements.

Potential is only good if it’s realized, after all, and in this case, if feels like Rotor may have bitten off more than it could chew. I sincerely hope that Rotor can continue to refine Uno to the point where it’s as good as the company imagines it can be, and for the sake of Pablo and Ignacio — not to mention everyone else who works at Rotor — I hope the company can do so without choking along the way.

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