Shimano claims the new DURA-ACE 7900 group, subtitled “Evolution of Perfection”, sets a new benchmark in top-level road racing components. Besides offering a further improved performance and an attractive design, the weight is reduced significantly.
Claimed to offer completely new engineering features, the FC-7900 crankset is a reworking of the 7800 Hollowtech II design, but with the added refinement of a hollow-rim outer chainring to boost stiffness by around 20percent. All-up weight is reduced by 15g without loss of overall rigidity. The bottom bracket bearings feature improved sealing.
There is a wide choice of chainring combinations: 53/42T, 52-39T, 53/39T, 54/42T, 55/42T and 56/44T. Crank arm lengths run from 165mm to 180mm in 2,5mm increments. For the first time there’s a DURA-ACE compact crankset. It’s called FC-7950 and is available with a 50/34T chainring combination.
Dual Control Levers
The new Dual Control Levers feature carbon fibre lever blades. Shift cables are now concealed under the handlebar tape thanks to the development of a new internal mechanism that retains the familiar Shimano STI operation.
The levers are adjustable for reach to make them adaptable to smaller hands and a wider selection of bar shapes. The hoods have been redesigned for increased comfort and the shift lever has a 20% shorter stroke for faster shifting.
Integrated buttons on top of the hoods operate the new wireless Flightdeck computer without the need to take the hands of the handlebar. The new Flightdeck computer can be used to make a wireless connection with a PC to analyse riding data (software is included). The Dual Control Levers are over 40 grams lighter than the current version at 378 grams per pair.
New bar end shifters and down tube shifters will be available to match the new Dura-Ace group. A carbon brake lever for aero handlebars, coded BL-TT79, will be available for time trial and triathlon usage.
The new Dura-Ace chain has an asymmetric design and features redesigned inner plates for improved contact with the cassette sprockets. Remodelled outer plates reduce the chance of chain suck. The chain sports hollow pins and perforated inner plates to make it lighter. Weight is 252 grams, saving almost 30 grams over the current version.
Introduced alongside the chain is the SM-CN79 ‘quicklink’. Allowing the chain to be split and joined without using any tools, it is compatible with other Shimano 10-speed chains as well…
The rear derailleur has a wide gear ratio and can be used with sprockets up to 28 teeth. It is compatible with the use of a compact crankset without the need for a medium cage derailleur. It has a full carbon pulley plate and a carbon/resin composite P-body that helps to reduce the weight to 166 grams.
The front derailleur has a lightweight design and an optimum spring tension for feather light downshifting. Trimming the outer chainring is no longer needed to allow a better concentration on the ride. The efficiency has been improved by using a stiffer and solid wide link design. Weight is only 67 grams.
The brakes feature new compound blocks that double brake performance in wet circumstances, improve stopping power in dry weather by 20% and offer greater durability.
The brakes have an enhanced brake arch proportion for an increased linear response. A lower cable stopper ensures a better cable routing and reduced cable friction. The dual pivot bolt and center bolt as well as the inner cable fixing bolts are made of titanium, getting weight down to 293 grams per set.
The cassette is based on a super lightweight yet very rigid aluminum sprocket carrier and will be available in a wider variation of combinations: 11-21T, 11-23T, 11-25T, 11-27T, 11-28T, 12-23T, 12-25T, 12-27T. The four biggest sprockets are made of titanium. Weight is 163 grams (11-23T).
The hub and freehub are more rigid, improving rotation even when the quick release is tightened strongly. Furthermore, they have been developed with a completely new bearing adjustment system that enables easy adjustment by hand without the use of a cone wrench.
More info at www.dura-ace.com
Availability in the market: October 2008.