After months of speculation, leaks, but little actual info, Shimano’s highly anticipated hydraulic road disc brake system is finally here. Oh, and there is a new 11 speed Ultegra Di2 group as well. At this point in the game, Shimano trickling down the new features from Dura Ace 9070 is just about a given, but there are some great updates to an already amazing system. I’ve been on an Ultegra 6770 Di2 equipped bike for the past few months, and riding is believing. With 6870 only promising to be better, the future is looking bright for Shimano electronics – and road discs.

Want more on Shimano’s first hydraulic road disc/Di2 system? Find it all with exclusive tech and insight directly from Shimano after the break!

Now for the reason you’re all here – Shimano’s R785 hydraulic system. While you may have been expecting to see a specific Ultegra branded system, the Ultegra-level system allows it to exist on its own, since it’s not a complete drivetrain. The beauty of the ST-R785 shifters and BR-R785 hydraulic disc brakes is that thanks to the E-Tube wiring system, the R785 group can be added to any E-tube equipped Di2 group. That means Dura Ace 9070, new 11 speed Ultegra 6870, and 10 speed Ultegra 6770. We asked Shimano Road Product Manager Dave Lawrence about the cross compatibility, and he said since the rear derailleur essentially tells the shifter what to do, the ST-R785s are basically plug and play for any E-Tube system. He did mention that older 6770 systems that have not been updated recently may need a firmware update, but other than that they will all work together.

The same goes for upgrading a 6770 10 speed Di2 group to 11 speed – the drivetrain would need to be replaced, but you could keep the 6770 shifters as they will be compatible with the 6870 parts. Of course if you go that route you will miss out on the addition of a 3rd port on the shifter for use with the SW-R610 sprinter shifters. Shimano has also continued to improve the ergonomics on the 6870 shifter with easier access to the shifter buttons, and increased contrast in texture between the two buttons. Like Dura Ace 9070, the 6870 shifter can be customized with variable multi-shift speed and shift count when you hold down the button in addition to firmware updates rolling out in the future.

Side by side, perhaps one of the best features of the ST-r785 is how similar it is to a standard Di2 lever in size and shape. Thanks to the relatively tiny internals for an electronic vs. mechanical shifter, there is plenty of room for the hydraulic master cylinder. The result is a shifter without any additional girth in order to squeeze in the hydraulics. Built into the ST-R785 lever are also reach and free stroke adjustments allowing riders to dial in the perfect position and obtain more braking power from the hood.

One of the big questions on everyone’s mind when it comes to Shimano’s road discs will likely be – what about the heat? According to Shimano, for them – it’s a non issue. Boldly showing their confidence in their technology, Shimano is recommending 140mm rotors front and rear for the road, regardless of weight – as long as you are using the SM-RT99 IceTech Rotors and Ice Tech finned pads. The rotors are identical to the rotors recently launched with the new XTR brakes, that were initially developed for Saint brakes. These rotors use the IceTech aluminum core clad in stainless steel, but take it a step further with the aluminum core flowing out into the center of the rotor in the form of “Freeza”cooling fins that help to further radiate heat. Shimano points out that the finned brake pads can reduce heat build up by 50° with another incredible 150° of cooling offered from the RT99 rotor compared to a standard steel rotor. While 140mm rotors are recommended front and rear, SM-RT99s will be offered in 140, and 160mm.

When asked what allowed Shimano to be so confident in the heat management of such small rotors, Lawrence stated it’s due to all of the research and development of the IceTech system from the mountain bike side of the business. “Our knowledge of heat management from mountain bikes is what allowed us to create this system,” said Lawrence. In fact, when asked if the BR-R785 was developed specifically for road bikes, we were told it was essentially a re-purposed mountain bike brake caliper that has been tuned for road use. That means the aluminum caliper uses the same brake pads as most of the current two piston Shimano mountain bike brakes offering consumers easily available replacement pads.

The other great news for the system is that it uses all of the same hose fittings as current hydraulic systems and is bled with the same method as well. Hoses will attach to the levers with the standard Shimano olive and barb with a threaded barrel, and the bleed system uses the Shimano bleed funnel at the lever with a syringe at the caliper. According to Lawrence, “The First prototypes actually had a different bleed process. But going into the road side of things, we knew some shops are road specific so they may not have as much experience with disc brakes. Realizing that meant having a consistent bleed process across the board was important.”

Since Shimano requires the use of the SM-RT99 rotors to guarantee proper heat management, that also means users will be forced into Centerlock rotors as the RT99 is not offered in 6 bolt. In order to provide something to roll on, launching along with the BR785s will be a set of 11 speed compatible Centerlock hubs and wheelset. The HB-CX75 hubs will be offered in 28 hole drilling, are 11 speed compatible, and can accommodate a 140mm rotor.

The Wh-RX31 Centerlock disc wheelset is specified for road and cyclocross use and are standard clinchers with a slightly wider 17mm internal width for better suiting wider tires. Both the hubs and wheels will be available in 135mm rear hubs only. We asked if more wheels and hubs were in the pipeline and Dave said there would be higher end options introduced in the near future along with companies other than Shimano working on compatible wheels and hubs.

Almost overshadowed by the hydraulic discs, the new 11 speed Ultegra Di2 includes the expected extra gear, but also drops a total of 126g and adds some new features as well. One of the most welcome is a redesigned rear derailleur that has a wider link for better shifting and is offered in a mid-cage GS version which will allow up to a 32t rear cog – a first for Di2. Combined with the new Ultegra 4 arm crank that was unveiled with the 11 speed mechanical group, the 6870 group offers a wide range of gearing so almost all riders can find the perfect set up. Cranksets can be configured in 53-39, 52-36, 50-34, and now 46-36 for cyclocross.

6870’s E-Tube wiring system is also updated to offer a cleaner install while making the addition of satellite shifters and special programming easier.

As mentioned, the new ST-6870 shifter now has three ports that will accommodate the additional Sprinter shifter and satellite shifter. The SW-R610 Sprinter shifter is not compatible with 10 speed Ultegra levers. The other big news for Ultegra 6870 is the introduction of the ST-6871 or Ultegra specific TT shift/brake levers. The brake lever shifters aren’t pictured, but the system offers the same multi-position shifting and braking while maintaining E-tube functionality.

Weights:

In order to drop the 126g over 6770 Di2, you will need to use the internal battery for the system, for a combined total weight of 2359g. Otherwise, with the external battery the 6870 Di2 system is only 69g lighter but hey, lighter weight and another gear is good, right? 6870 is also 9g lighter than 6800 mechanical with the internal battery. Weights are with an 11-23 cassette, 114 link chain, and a 170mm 53-39 crankset.

As for the R785 system, the complete system including shifters, brakes, hoses, mineral oil, and two RT-99 rotors works out to be 1066g. Compared to 6870 shifters with rim brakes, the hydraulic system adds less than a pound – somewhere around 340g.

R785 Weights:

ST-­R785 – 515g

BR-R785 – 263g

Brake Hose (BH59) – 61.5g

Mineral Oil – 21.5g

Rotor – RT-99 (140mm) – 205g

Availability:

Availability for all all parts is expected in November with Shimano holding off on setting pricing due to possible fluctuations in the exchange rate between now and then. Until then, Shimano’s sponsored athletes will continue testing, but you can probably expect to see the new R785 system on a cyclocross course near you, this fall.