Gear News

Shimano releases Ultegra clutch rear derailleurs with drop bar shifting compatibility

Clutch technology borrowed from mountain bikes and designed to eliminate dropped chains

Shimano is attempting to smooth out your future rough road adventures with the inclusion of clutch technology in its latest Ultegra RX rear derailleurs. In fact, keep your eyes peeled for Shimano’s latest tech on John Degenkolb’s bike at this Sunday’s Paris-Roubaix.

Available in both mechanical and Di2 configurations, the RX800 and RX805 rear mechs provide the option of increased chain stabilisation to drop bar devotees seeking adventure beyond the paved road. Beyond Ultegra RS, Shimano has also launched the latest 105 R7000 groupset with dedicated disc brakes.

What is clutch technology?

We’ll forgive you if clutch technology is new to you, as while Shimano has been providing the technology to mountain bikers for a number of years, it’s been absent from the company’s road product line-up until now. Indeed, while SRAM has offered a clutch rear mech for single-ring road/cyclo-cross setups since 2014, this is the first design compatible with a front derailleur.

When you hear the word ‘clutch’ you’ll most likely think of a car, but there’s no extra lever to pull when shifting or anything like that; the ‘clutch’ in this instance is a mechanism within the rear derailleur which provides greater chain tension so, as a rider, you’re less likely to drop a chain or hear that niggling chain-slap noise that indicates your chainstays are taking a beating.

Shimano has introduced its clutch technology to the Ultegra RX800 and RX805 rear derailleurs (Pic: Shimano)

The clutch provides the effect of massively increased spring tension within the shifting mechanism, inducing more tension into the chain and in turn less margin for error with regard to shifting. In other words, it stops the chain flailing wildly on poorly maintained roads. The clutch mechanism can also be disengaged using a thumb actuated lever on the rear mech itself, reducing the tension to that of a normal derailleur or simply for making the process of changing a wheel or chain a little easier.

Why now?

Only a few years ago, attending any niche handmade bicycle show would result in the feeling that fat-tyred bikes were going to take over the world. Thankfully they didn’t, but these days ‘gravel bikes’ are the must-have addition to any bicycle manufacturers line-up, and Shimano has taken notice:

Riders have been pushing the limits of what a road bike is capable of riding for many years, evolving the sport from racing to encompass greater adventure,” says the Japanese firm. “In recent years we’ve seen a broader definition of what a drop handlebar bike can look like; road wheels followed that by accommodating wider tyres. Now in a natural evolutionary step it’s time for drivetrains to evolve too.”

When a typically reserved manufacturer of Shimano’s magnitude publicly announces the acknowledgement of a trend you know it’s here to stay. Until now, the only option available to tech-hungry explorers was to mix and match Shimano’s MTB and road Di2 groupsets. While cross-compatibility is a means to an end, any manufacturer will be the first to tell you it will never work quite as well as a product designed specifically for purpose. On top of that, if you’re a drop bar mechanical groupset user (and let’s face it, the vast majority of us are) then the option of a clutch has been nothing but a pipe-dream until now.

Trek-Segafredo’s John Degenkolb is expected to run the Ultegra RX805 rear mech at Paris-Roubaix


The Ultegra RX derailleurs are designed to be compatible with all of Shimano’s drop bar 11-speed dual control levers, with Di2 setup as usual and mechanical featuring the same pull ratios as all other 11-speed derailleurs in the road product line, meaning that upgrading an existing groupset is likely the obvious option for many.

The RX800 and RX805 derailleurs offer up increased range for larger cassettes too, now catering for anything up to a 34-tooth sprocket as the lowest climbing gear. Riders with a more traditional setup can rest easy; Shimano has reassured us the shifting is just as crisp across all sizes of cassettes.

Shimano Ultegra RX800 and RX805 rear derailleurs
Shimano Ultegra RX800 and RX805 rear derailleurs
Shimano Ultegra RX800 and RX805 rear derailleurs

When shifting mechanically, the increased tension is designed to be hardly noticeable. Once the initial inertia of the clutches grip is overcome it feels much the same as any other mechanical shift. The rear mech yields easily under one’s input at the handlebar but gives the bumps of the road a far harder time.

The advantage of a clutch mechanism having been available to mountain bikers for so long is that the technology is already proven to work at the highest levels of performance. The benefits to professional road cyclists are less obvious – with increased chain tension comes the marginal loss of precious watts – but for the cobbles of the Spring Classics, the extra chain security may may prove advantageous.

The Hell of the North, which Degenkolb won in 2015, will be the ultimate testing ground for the new tech (Pic: Sirotti)

Trek-Segafredo’s Degenkolb is rumoured to be taking the RX805 Di2 rear mech into battle at Sunday’s 116th edition of Paris-Roubaix, an event which ‘Dege’ won in 2015. The race is renowned for its harsh terrain, and if Degenkolb’s previous performance is anything to go by, this should be the ultimate test for the new product; any questions about reliability will surely be put to rest.

For the rest of us, Shimano’s new RX800 and RX805 rear derailleurs will be available to consumers from mid-June this year. UK prices are to be confirmed.

Website: Shimano

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