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Leaked photo shows Shimano have developed Di2 hydraulic disc brakes for the road

So long as the big players were absent from the hydraulic road disc debate, you could pretty much come down on either side. But if Shimano and SRAM both think it's going to work, then it's probably time to sit up and take note.

Michiel van der Heijden rides cyclocross for the Shimano-sponsored Rabobank team and he helpfully posted a snap of his bike on Twitter yesterday before heading off for a ride. Not just any old bike, though: a previously unseen disc-only Carbon Giant CX frame running Di2… and hydraulic discs.

There's no official word from the component manufacturer on this kit so we're stuck with what we've got in the pic, but with no master cylinder visible anywhere on the bike it's obviously in the lever hood. We'd expect that, anyway: with Di2 there's precious little else in there so there should be plenty of room.

Spy shots of the SRAM system made it look like they were struggling to fit the cylinder in; Shimano's lever is more or less the same shape as a mechanical one. The drivetrain is Dura-Ace but the levers appear to be Aluminium; whether that's just because they're prototypes is anyone's guess.

The callipers themselves look a fair bit like Shimano's M785 XT units; they're the same shape and you can see the cooling fins of the Ice-Tech pads poking out of the top. Heat build up has often been touted as the main issue for discs on the road so it would make sense to use that technology which allows the brakes to run significantly cooler.

The rotors are both 140mm, probably XTR-level RT98s. This is a CX bike, so it won't necessarily be going near any long alpine descents; we'll wait and see what rotor sizes Shimano go for on the roadgoing versions of this system which will surely follow. They're bolted on to Shimano-branded wheels with what looks like a carbon rim and a 2-cross lacing, but they could be pretty much anything.

Giant have a close working relationship with Shimano; last time we went out to a press launch with them (for Ultegra Di2) the kit was bolted on to pre-production samples of the new TCR Advanced frame. In fact, it was the first time we got to ride it. So it wouldn't surprise us if they were working in tandem with Shimano on this in order to work towards a launch sometime later in the year. All, as they say, will be revealed...

The disc brake revolution is coming, then. Have a read of our industry insider article on the future of disc brakes.

David has worked on the road.cc tech team since July 2012. Previously he was editor of Bikemagic.com and before that staff writer at RCUK. He's a seasoned cyclist of all disciplines, from road to mountain biking, touring to cyclo-cross, he only wishes he had time to ride them all. He's mildly competitive, though he'll never admit it, and is a frequent road racer but is too lazy to do really well. He currently resides in the Cotswolds.