At Eurobike 2013, Shimano unveiled its first hydraulic disc brake for road and cyclocross bikes. It performs at the level of the renowned Ultegra groupset. Interestingly, however, it is not compatible with mechanical shifting components. This is the only aspect that distinguishes the Japanese model from those SRAM has released to date [regardless of the recall – link ]. Over the past two months, we have put both the Ultegra 6870 Di2 and the hydraulic brakes through their paces in winter conditions.
It's not so easy to find a frame that performs well both on and off-road and allows for the installation of an electronic groupset and disc brakes. The Specialized Crux, however, meets these requirements.
In addition to the current Ultegra 6870 Di2 groupset with seatpost battery, and 46- and 36-tooth chainrings on the crankset, we've also installed the new Ultegra brake calipers and Centerlock rotors from the XTR series. These are paired with a 160mm rotor at the front and a 140mm rotor at the rear. The setup is completed by the equally new Shimano RX31 clincher wheels.
The installation is relatively straightforward. The cables of the Ultegra 6870 Di2 are routed internally through the frame and can be connected to each other with the usual ease. Routing the brake lines is also largely trouble-free. While one end of the lines is connected to the calipers for the front and rear brakes, the shift levers also have integrated lines. Once all the cables are routed, they are joined together using the provided connectors. To prime the brakes, you first need to remove the top cap of the levers. After that, the brakes can be activated like any other hydraulic brake from Shimano.
Although the front derailleur and rear derailleur can be programmed using dedicated software that is only available for Windows computers - here the options range from determining the shift jumps to programming the left lever for the rear derailleur and vice versa - they don't have to be. Actually, you only have to set the stops, the rest is done by both components themselves.
The first thing you notice when using them is the shape of the levers. Compared to conventional Ultegra levers, they feature a significantly higher horn, which is, however, slightly lower than that of their American competitors. Aside from that, they feel good in the hand, although it takes some getting used to gripping the levers in the way you're accustomed to on a road bike.
The shifting performance is beyond reproach. While the Ultegra 6870 Di2 is n't quite as crisp as its significantly more expensive counterpart, the Dura-Ace 9070 Di2 [ Link ] , the difference is barely noticeable – only the overall weight of the system is slightly higher. A major advantage is that the Ultegra 6870 shifts superbly even under load. This is particularly noticeable on climbs and off-road. It's only when used on rough terrain that the true strength of the electronic shifting system becomes apparent. Thanks to automatic chain alignment, the chain always stays exactly where it should be. Chain slap doesn't impede propulsion.
The brakes also proved to be highly refined. They showed no signs of weakness, neither on short descents with average gradients of up to 12 percent – unfortunately, the winter weather prevented longer descents in the mountains – nor during use under truly adverse conditions. We experienced no fading whatsoever. On the contrary, they always provided powerful and reliable braking. Thanks to the low hand force required, they are particularly suitable for cycling marathon enthusiasts, but also for riders with smaller hands, especially women and children. Anyone accustomed to using a standard rim brake will certainly need to adjust, as Shimano's hydraulic stoppers definitely redefine the concept of braking pressure . And in a direction more commonly associated with mountain biking. The brakes performed reliably regardless of the weather conditions, and even in sub-zero temperatures, they presented hardly any problems; the noticeable pressure point was slightly delayed, but the difference remained minimal. This makes the brake particularly interesting for those who swear by carbon wheels but struggle in wet and cold conditions . When riding in mud, the brake discs may rub, but this usually resolves itself relatively quickly.
//Conclusion
With the Ultegra 6870 Di2 and hydraulic disc brakes, Shimano has launched a groupset that the competition must now emulate. Thanks to its low mounting position at the fork ends, the often annoying brake judder typical of cantilever brakes on cyclocross bikes is eliminated. In terms of both shifting and braking performance, this groupset elevates riding enjoyment to a new level in its price segment.
//Product highlights
- very good brake pressure in all conditions
- easy maintenance of the brakes and the groupset, battery lasts a long time
- Switching performance without ifs and buts
//price and web
- no official price information from Shimano
- www.paul-lange.de