Sicily has already been the centre of one revolution that influenced the course of history. In 1860, the freedom fighter Giuseppe Garibaldi initiated the founding of the Italian nation state from here.
A good 150 years later, on the slopes of the Etna volcano, the component manufacturer Shimano presents an ensemble of road bike components that future generations will perhaps also categorise as revolutionary in retrospect. The fully hydraulic BR-R785 road bike disc brake, which is only compatible with the Di2 electric drivetrain, makes it possible for the first time to build road bikes without Bowden cables. Shimano is thus combining two technologies which, although not brand new in themselves, could not previously be reconciled.
Simple solution
In spring 2013, Shimano's competitor SRAM was the first component manufacturer to present fully hydraulic disc brakes for road bikes. However, the brakes, which are available in three quality levels, can only be combined with mechanical shifting systems from SRAM. The BR-R785, on the other hand, was designed from the outset so that it can only be combined with Shimano's electric shifting system. A solution that was probably also favoured by the fact that it was technically quite easy to implement. Because the Di2 does not require bulky mechanics in the brake levers, the hydraulic cylinders could be placed relatively easily inside the lever bodies. The levers of the BR-R785 are therefore hardly more bulky than their mechanical counterparts - and significantly more compact than those from SRAM.
The reason why Shimano has not given its youngest child a catchier name is that the BR-R785 is not assigned to a specific groupset. It can be combined with the Dura-Ace Di2 as well as with the brand new Ultegra Di2, which was available for the first time for riding tests in Sicily. The road bike remains a road bike, even with hydraulic brakes and electric shifting. This is the first impression of the practical test. The difference in braking behaviour between the BR-R785 and modern rim brakes is noticeable, but not galactic - at least when the roads are dry like on Mount Etna. Pleasingly little manual force is required to brake the test bike from high speeds of over 70 km/h with pinpoint accuracy and control, and the pressure point is clearly defined.
The positive impression is qualified by the fact that modern rim brakes also decelerate impressively well, as a direct comparison with a bike with new Ultegra brakes makes clear. However, the BR-R785 has one advantage over rim brakes. Even from the brake lever position, it converts comparatively low manual force into high braking power, also thanks to the ergonomically excellent levers. In the event of sudden emergency braking, this can provide those tenths of a second that might prevent a fall. This would also benefit the many racing cyclists who prefer to ride down long descents in the more upright brake lever position rather than the actually safer lower handlebar position.
Advantages in wet conditions
However, the BR-R785 will show its decisive advantages in conditions that the testers were spared in Sicily. There is no doubt that disc brakes offer serious advantages over rim brakes, especially in bad weather. Braking performance on wet roads is more predictable and braking distances are significantly shorter. As the rims no longer act as friction partners for the brakes - and therefore as wearing parts - there will also be no more heat-related tyre bursts.
However, early adopters who can't wait to switch to the new technology will have to accept two drawbacks: The BR-R785 does not make road bikes lighter. Shimano puts the handicap at around 200 grams compared to a comparable conventional bike, based on the overall system including mounting bases on the frame and fork as well as special hubs. However, the comparison is somewhat misleading, as the decision to use disc brakes means that tuning options such as super-light carbon wheels and 300 gram forks are no longer available. A standard racing bike weighing less than six kilos with disc brakes remains a dream of the future for the time being. However, a total weight of seven to eight kilos seems realistic. In addition, racing cyclists who switch to disc brakes will have to be prepared for a problem that has so far mainly been experienced by mountain bikers. If the mounts for the brake callipers on the frame and fork are not milled exactly flat, as was the case with our test bike at the beginning, every ride will be accompanied by more or less loud grinding noises. The main thing here is for frame manufacturers to keep the manufacturing tolerances as tight as possible.
Well chilled
One point of particular interest during the practical test with the BR-R785 was the heat management of the brakes. Sensitised by our experience with other mechanical and hydraulic disc brakes (see report in TOUR 11/2013), we tried to test the limits of the new brakes by deliberately operating them incorrectly. The good news: even after kilometres of downhill riding with the brakes dragging, the braking performance did not decrease significantly. Shimano pulled out all the stops to ensure the best possible cooling to prevent the dreaded fading - the heat-induced reduction in braking performance that can lead to total failure: Ice-Tech brake discs, which have an aluminium core between the stainless steel braking surfaces, heat up less than conventional brake discs, as TOUR measurements have already shown. For the BR-R785, Shimano has also modified the Ice-Tech discs so that the surface of the aluminium core is enlarged towards the hub by cooling fins. Shimano calls this solution Freeza. In addition, the backing plates of the organic brake pads were given protruding cooling fins. Ice-Tech and Freeza supposedly reduce heat development by 150 degrees compared to comparable brakes.
Shimano therefore optimistically assumes that brake discs with the small diameter of 140 millimetres will be sufficient for most cases, even on the fork. It's difficult to say what to make of this, as the test bikes were fitted with 160 millimetre discs and, as already mentioned, there were no problems; the first impression of the BR-R785 was very convincing. However, the Etna descent was not extremely steep, with an average gradient of 7.9 per cent, and the system weight of the rider and bike was less than 80 kilos. Further tests are therefore necessary before a final assessment of the brake can be made. Shimano is not quoting prices for the BR-R785, as it is unlikely to play a role as a retrofit option for the time being due to the still small number of compatible frames. Complete bikes with the potentially revolutionary brake are available from around €3,500.
