IRVINE, CA (BRAIN)—Shimano gives its top of the line road group an entirely new look with design elements integrating the crank, derailleurs and brakes together, just like on XTR and XT. Shimano says Dura Ace FC-7900 Mechanical groups will be available this fall, but there is no word yet on when its electronic drivetrain will hit the market.
The new group is 135 grams lighter than current Dura Ace, but the company worked to increase stiffness and durability while taking the weight out. For example, the new FC-7900 crankset is 15 grams lighter, yet it is 20 percent stiffer then the crank it replaces. The crank features a new hollow outer chainring, which is a big contributor to its weight savings and increase in stiffness. And like XTR and XT, the new road crank adds adjustable side-load preset.
The ST-7900 dual control levers have a new ergonomic shape, reach adjustment for the levers, Shimano’s first carbon fiber lever and under handlebar tape housing runs. The levers are 40 grams lighter than last year and the shift stroke for the rear derailleur is noticeably quicker. Shimano’s integral cycle computer, Flight Deck, now includes heart rate, altitude, grade, cadence and gear position and is downloadable via a wireless connection.
The rear derailleur loses 16 grams, partly from a switch to carbon fiber pulley cage, and now works with cogs up to 28 teeth, expanding its use with compact cranksets. Cassette design is lighter, the largest four cogs are titanium. Available combinations will be, 11-21, 11-23, 11-25, 11-27, 11-28, 12-23, 12-25 and 12-27 teeth.
The enhanced linear response of the BR-7900 brakes comes from a redesigned caliper arch with lower profile cable stops to create better lines for the cables and reduce cable friction. And Shimano trimmed brake weight by 30 grams yet kept the spring tension adjuster and adjustable toe-in features.
Dura Ace’s new chain has an asymmetric chain plate design that reduces the chance for chain suck on the chainrings. And in a big departure from its Hyperglide connection pin, the SM-CN79 quick-link provides a reusable connection. The quick-link can be used on any Shimano 10-speed chain and the new chain can also be joined by a traditional Hyperglide 10-speed connection pin if necessary. The chain also uses hollow pins and weight drops by over 18 grams even with the addition of a quick-link.
—Matt Wiebe
