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Larger version: http://light-bikes.com/BikePhotos/web_pics/DA7900big.jpg
FC-7900 Dura-Ace crankset
The new Dura-Ace crankset features a hollow outer chainring. Likely due to the ring and further refinement of its hollow forging process Shimano claims the crankset is 20 percent stiffer and 15 grams lighter than the 7800 edition. Other changes include redesigned chainring teeth said to improve chain interface and power transfer, as well as improved bottom bracket seals to reduce contamination and friction. The new crankset does not adopt Shimano’s 970 XTR non-drive crank arm attachment; instead it retains the pinch-bolt style design of the old crank.
After a long wait Shimano will also carry a Dura-Ace branded compact crankset (34/50) with the 7900 series group.
The latest word of Shimano’s yet-to-be-sold Carbon Dura-Ace crank is that it will keep the 7800 series designation and chainring style. Its revised release date is later this year, likely fall.
FD-7900 Dura-Ace front derailleur
Shimano claims its new Dura-Ace front derailleur cage design eliminates the need to manually trim the front shifting, therefore the extra detents have been eliminated. The redesigned front derailleur linkage is wider and the spring is tweaked to reduce the effort required at the shift lever. This is a tough one to stomach, as the absence of trim for both chainrings is one of our top gripes when it comes to SRAM’s road groups.
RD-7900 Dura-Ace rear derailleur
The rear derailleur further illustrates the brand’s acceptance of carbon fiber with a carbon fiber pulley cage. The rear derailleur loses another 16 grams. The new mech is compatible with wider range cogsets and can accommodate up to a 28-tooth cog.
ST-7900 Dura-Ace Dual Control levers
The new STI Dual Control levers offer a refined ergonomic shape and are claimed to be 40 grams lighter. 7900 will be known as the group in which Shimano fully accepted carbon fiber. The new STI levers feature unidirectional carbon fiber lever blades, which are responsible for much of the reduced weight. Shimano also took the opportunity of a lever redesign to tuck both the brake and shifter cables under the handlebar tape, putting it in line with its competitors. The shifters are held to bars via titanium clamps and bolts. Shimano claims that the revised internal mechanism along with a new PTFE-lined casing keep the action as light as previous designs.
The shift stroke for the rear derailleur has been reduced by 20 percent for quicker shifts, but a 7800 rear derailleur will work with the new group and vice versa. A built in reach adjuster allows for fine-tuning the fit for riders with smaller hands.
The shifters continue to offer integrated controls for a new FlightDeck computer (SC-7900), which has been updated to include heart rate, altitude, grade, cadence, gear position, and is directly downloadable via a wireless connection. The new SC-7900 computer is completely wireless via the use of a coded frequency.
BR-7900 Dura-Ace brakes
According to Shimano its new Dura-Ace brakes have “Increased linear response, improved braking power and reduced weight.” In addition the company claims that its new brake pad compound doubles wet condition performance, while improving dry power by 20 percent. If this proves true, Shimano will have a brake that’s untouchable in terms of power; the current version still serves as the industry’s benchmark. The “increased linear response” is spawned from a redesigned caliper arch, while the cable stop is lower profile, creating smoother cable routing, which is said to reduce cable friction. The brakes feature a spring tension adjuster and adjustable toe-in for the pads while dropping nearly 30 grams from the combined front and rear calipers.
CS-7900 Dura-Ace cassette
Shimano claims further shifting improvements by creating a stiffer and lighter aluminum carrier along with re-engineered tooth profiles. The largest four cogs are titanium. Shimano claims the cassette is 10 grams lighter. The 7900 Dura-Ace cassette will be available in the following combinations: 11-21, 11-23, 11-25, 11-27, 11-28, 12-23, 12-25 and 12-27.
|Components||Dura-Ace 7800 Weight (Grams)||7800 (2008) Pricing||Dura-Ace 7900 Weight|
|Chain (116 links)||280||$50||262|
|Rear Hub 7850||267||N/A||N/A|
|Weight w/out Hubs:||2181||2052|
(2009 Dura-Ace 7900 pricing is not available)