Shimano's new hydraulic disc brake system uses the same technology found on its popular mountain bike brakes.

The hydraulic road disc brake system war is officially on. Just a few months after rival component maker SRAM came to market with its Red 22 hydro disc brake offering, Japanese giant Shimano has jumped into the game - as long as you are also running one of its electronic shifting groups.

Indeed, the new braking technology (called R785) is a melding of existing Di2 electronic shifting with Shimano's ICE Technologies hydraulic disc brake heat management system that is well-known in the mountain bike world. The R785 groups is actually not a group, just an Ultegra-level Di2 shifter, caliper and rotor that are cross-compatible with any E-tube equipped Di2 group, be it Dura Ace 9070, 10-speed Ultegra 6770, or the new 11-speed Ultegra 6870, which was also unveiled this week (more on that later).

Pricing for the new disc brake components has yet to be released and the system wont be available until sometime in November, though we'd be surprised if it doesn't show up as spec on 2014 model year bikes hitting shop room floors earlier in the fall.

Perhaps the biggest initial take-away is Shimano's unblinking confidence in its new braking system. While SRAM is recommending 160mm rotors for paved use and 140mm for cyclocross with its system, Shimano says 140mm will work in all applications - and for all rider weights.

"As long as you are using our ICE-Tech rotors and pads, we are confident in the 140mm recommendation," said Shimano road product manager Dave Lawrence, adding that there will also be a 160mm option for those who prefer a larger rotor size.

The ICE-Tech rotor is claimed to provide superior stopping power in all conditions.

The R785 rotors are essentially identical to the recently launched XTR brake rotors, and include the fin-shaped brake pads Shimano claims can reduce heat build-up by upwards of 50 degrees, a number that increases a further 150 degrees when you add Shimano's RT99 rotor and contrast that against a standard steel rotor. Those ICE-Tech rotors have what Shimano calls FREEZA fins, which add surface area without increasing rotor size. Dual-piston calipers further increase braking power.

Troubling to some will be the fact that the new RT99 rotors are centerlock only. Perhaps not coincidentally Shimano also launched a new road disc wheelset (WH-RX31) that has no rim brake track, and accommodates 140mm and 160mm centerlock rotors.

The other big takeaway is weight - as in added weight. Lawrence estimates that running disc brakes will include "about a 300-gram" weight penalty and our math puts it more in the 330-340 range. It's for this reason that, while a huge fan of the technology, even Lawrence admits that traditional rim braking systems aren't yet in danger of rapid extinction.

"I think at least for now, there will still be a lot of people that want to stay with rim brakes," said Lawrence. "Even for me it's a tough call. We don't get a lot of rain out here, which is where you see some of the biggest benefit from a braking standpoint (when using disc). Plus our rim brakes obviously work very well and I am very confident using them. But on those rainy days, I jump on my disc-brake-equipped bike when I'm riding into work and feel a lot more confident."

The other perhaps more immediate application will be in cyclocross. Already last year, disc brakes became a common sight at top-level UCI races in the U.S., and Lawrence suspects adoption by top World Cup level riders will happen as soon as the weight penalty is wiped out.

"Anyone who has ridden disc for 'cross understands how much more control you have," said Lawrence, alluding to the fact that you can brake later in corners with more power and better modulation. "That is something that is definitely confidence inspiring. But if you look back to the transition from V-brakes to disc brakes in top level mountain bike racing, the tipping point only came when there wasn't a weight penalty anymore. That's why it may take a little more time. I also think it goes hand in hand with frame development. These first generation road and cross frames that are disc compatible have some weight penalty, as well. But as the technology evolves and understanding increases, we'll see fuller adoption. It's one of those things that you really have to get people on it. Then they understand."

As for the new R785 shift levers, they offer the full menu of E-tube compatible shift options, including Shimano's sprint and climbing shifters along with the ability to adjust shift speed and shift count. Firmware updates will allow for upgrades over time.

Finally it's worth noting that Shimano's disc brake system utilizes the same hose fittings and bleed techniques as its current mountain bike hydraulic systems, which means there wont be as big a learning curve for shops or home mechanics. "Even most of the small parts carry over from mountain biking to the road system," noted Lawrence.

Oh yeah, Shimano also unveiled its new 11-speed Ultegra 6970 electronic shifting system.

Somewhat overshadowed in all this is the new 11-speed Ultegra Di2 6870, which adds a gear, drops a net of 126 grams if you opt for an internal battery, and now includes a mid-cage derailleur option that will accommodate a 32-tooth rear cog, something Di2 has never had before. Up front, the new Ultegra 6800 crank, which we've already seen this year, features the four-arm spider and interchangeable chain rings that make it possibile to run 53-39, 52-36, 50-34, and now 46-36 gearing for cyclocross.

Pricing for the new Ultegra 6870 group is not yet available. And like the new disc system, it's slated to hit stores in November. You can learn all about those enhancements and more in the extensive photo gallery below.