RCUK cyclo-cross bike build 2013: part two – the groupset

Shimano's R785 hydraulic disc brake for road bikes installed

The second of our bike builds this winter has taken a great leap forward.

Armed with a Specialized CruX Carbon Pro frameset, courtesy of our friends at Specialized UK, we were acutely aware that the rest of the build had much to live up to.

Enter Shimano’s new hydraulic disc brake, the R785, first used by this correspondent on an exhilarating descent of Mount Etna, and its accompanying Di2 shift levers. As winter bike builds go, this is at the chintzier end of the spectrum. Many thanks to our friends at Shimano and their UK distributor, Madison. Let’s take a closer look.

The world’s best cyclo-cross racers have become early adopters of Shimano’s long-awaited hydraulic disc brake for road bikes, with world champion, Sven Nys, among those to sample their performance. We’re looking forward to doing the same.

Shimano have made no secret of the fact that the R785 is based heavily on their all-conquering XT mountain bike disc brake. While the rotors supplied with their off-road stoppers vary in size from 160mm to 203mm, the braking demands of road and even cyclo-cross bikes is reduced (lighter machinery, less extreme conditions), and with it the rotor size. Those fitted to our bike build are 140mm, and a 160mm is available too. We’re pleased to have an opportunity to test the smaller of the two road options having used the 160mm in Sicily.

Up front, we find the matching non-series STI lever, one whose pronounced leading edge betrays the presence within of a master cylinder for mineral fluid. Peel back the lever hood, as we have, to gain access to the reservoir: a necessity for ‘bleeding’ the system of air. Other features beneath the hood include a screw to adjust the ‘Freestroke’ – a facility to adjust the proximity of pads to rotor, and with it modulation.

The derailleurs are those from Shimano’s new 6870 Ultegra groupset: electronic and 11-speed. We experienced the shifting, errm, first hand on Etna (R785 lever isn’t compatible with mechanical systems, remember) and we can’t wait to find out how its superb performance responds to the demands of the trail. We’ll be able to form a fairly accurate assessment, given the recent arrival of the Lapierre Xelius EFI 600: a machine also draped in the Ultegra Di2 mechs, but paired with the groupset’s STI lever (and mechanical rim brakes) and not the R785 lever here.

Up front, we have a Shimano Ultegra 50-34 chainset and not the ‘cross specific 46-36 from the same group. Should our use for this magnificent machine extend to competition, we’ll swap out the rings. For now, it looks ideally suited to some ‘long way home’ road/trail adventures. There are playing fields, fire roads, sea-front pathways and more in our vicinity with this bike’s name on it.

Next week, we’ll take a look at the remaining components of this build, including wheels, tyres, and finishing kit.

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