Hands on Rotor's new UNO hydraulic road groupset

Image 1 of 14

UNO uses a single shift paddle system, somewhat like SRAM's DoubleTap(Image credit: Matthew Allen / Immediate Media)

This article originally appeared on BikeRadar

It’s not often that we get to try something genuinely new. The bikes we review are most often evolutions of existing designs, and most of the componentry we test aims to be lighter, stiffer, or cheaper than its predecessors, but it’s rarely fundamentally different. When we first caught wind that Rotor was planning to enter the groupset market we weren’t sure what to make of it. The market is dominated by Shimano and SRAM, with Campagnolo bringing up the rear. Rotor's UNO group is fundamentally different, in that it is hydraulically actuated. This isn't completely uncharted territory, however. The German company Acros already makes a hydraulic mountain group.

By moving the indexing mechanism to the derailleurs, UNO aims to ensure consistently accurate shifting. At the lever end, all you’re really doing is operating a hydraulic switch, meaning that the shift quality isn’t reliant on the hydraulics for its accuracy. As a result, Rotor anticipates extremely long service intervals – you’ll likely need to bleed the system after shortening hoses, but once set up it should work properly for years without intervention. In a similar vein, the braking system uses a non-water absorbing fluid (Magura Royal Blood), which reduces the need for frequent bleeding.

Available in two non-interchangeable versions for disc and (hydraulic) rim brakes, these have a lightweight carbon brake lever and a CNC’d aluminium shift paddle. The rubber hoods cover a fairly wide body, which Rotor says it designed for comfort based on rider feedback. Down the line, sizes may be available to suit different hand sizes. A screw allows for reach adjustment, but the bite-point is pre-set.

Shifting is somewhat similar to SRAM’s DoubleTap. The brake lever is for braking alone, and all shifting is carried out with the single paddle. A small push gets you smaller cogs (or the inner chainring), while pushing through to the second position moves the chain up the cassette or onto the big ring. Rotor hinted strongly that satellite shifters may be in development too, noting that it’s relatively straightforward to tap into a hydraulic line to add additional switches.

A work of CNC art, the rear derailleur is made from steel, aluminium, and a smattering of carbon on the cage. As the shifters are effectively just hydraulic switches, all of the indexing is built into the derailleurs and the jumps between cogs are permanently fixed. Because of this, there are no limit screws, and the only adjustment during setup involves turning a single bolt to align the derailleur with the cassette. We do wonder if this might be an issue in the event of a damaged hanger since there’d be no way to prevent the derailleur shifting into the spokes, but that’s likely a worst-case scenario only.

Our test ride seemed to indicate that front shifting was the groupset's biggest weakness. nevertheless, the front derailleur is a beautifully constructed object:
Like the rear, the front derailleur has no limit screws and relies on a single bolt adjustment. Once again, the indexing is entirely within the derailleur, and it has four positions – two for the inner chainring and two for the outer. Construction looks similarly polished to the rear, with some lovely machined details on the cage. The claimed weight for the front derailleur is 114g.

Compatible with standard Shimano/SRAM freehubs (and using the same cog spacing), Rotor’s cassette is manufactured entirely in-house. It’s made up of three major sub-assemblies, with steel used for the smaller cogs and aluminium for the largest two (CHECK). If you’ve got wheels with a Campagnolo 11-speed freehub and cassette these will work fine with UNO too, as the cog spacing is close enough not to matter. The claimed weight for an 11-28t cassette is 150g.

At the launch event in Spain, Rotor provided me with a Cervelo R3 Disc kitted out with a full UNO groupset (apart from a Shimano cassette and a standard KMC chain in place of the matchy-matchy UNO version). My test ride was abbreviated by poor weather in the mountains (snow in Spain in April! Who’d have thought?) but we managed 71km and nearly 1,300m of climbing — enough to get a feel for how the groupset behaved in the real world.

Initially braking was poor, but this purely down to brand new pads and rotors which hadn’t bedded in yet. After a little use I had no complaints – the lever feel is fairly linear, and while they don’t bite as hard as say, Shimano road discs, power from the Magura calipers is certainly ample. The lever shape works well from both the hoods and the drops, and we were happy to brake with one finger from the latter.

Shifting was the real unknown quantity. Although the principle is similar to DoubleTap, it feels quite different. With SRAM you feel like you’re compressing a spring, whereas Rotor’s shift feel is distinctly hydraulic in feel, more akin to pulling the brake lever on a mountain bike. It takes a moderate effort to move the shift paddle to its first position, and a fairly determined one to get to the second.

At the rear, this works rather well. I did most of my ride with the multi-shift feature turned off, and there was no faltering or inconsistency. Essentially, if you can handle DoubleTap, you’ll get on just fine with this. The front was slightly less impressive. For starters, with the chain in its outermost position (big ring, smallest cog) we experienced a little rub from the front derailleur cage. With no limits or cable tension to adjust, there’s not much that can be done about this (assuming the initial indexing setting is correct, which it appeared to be). One Rotor representative did comment that the Cervélo’s relatively short chainstays were right at the limit of specs, producing a less-than-ideal chainline.

More problematically, we had persistent issues with the chain refusing to drop onto the small ring under load. In a standard mechanical setup, a powerful return spring shoves the chain off the big ring. We’re not completely clear how the Rotor derailleur compares in this respect, but it certainly wasn’t as assertive as we’d have liked, and the ramping of Rotor’s outer ring was proving rather too effective, grabbing the chain back when we wanted it to drop down.

At the end of the ride I had a Rotor mechanic activate the multi-shift feature for a quick try-out. It can be set to allow two, three, or four downshifts in one go, so naturally I went for the full four. It does work absolutely fine, but it’s quite difficult to tell exactly how many gears you’ve shifted in a single sweep of the lever. There are no clicks to act as indicators, and the lack of mechanical feedback means you’d need to spend a lot of time honing your muscle memory for it to be useful.

The UNO groupset is at once hugely impressive and slightly frustrating. It’s a beautiful piece of engineering that’s truly original in a number of ways, and which appears to deliver on many of its promises: it’s light, seemingly practical from a maintenance point of view, and it does work. Some real-world niggles need addressing though, principally relating to the front shifting. We want to spend some more time with UNO before giving a final verdict, but we will say this: if you love clever engineering and are prepared to put up with some quirks, it’s a fascinating system that’s worth your attention. It’s not perfect, but it is very, very cool.