THIS WEEK IN PRO CYCLING
Tech Report: SRAM offers more details on '07 road group
Insisting on an embargo until Thursday, the SRAM corporation has releasedadditional information on the shifting mechanism behind the company’s newroad components, first introducedat the Eurobike tradeshow in September.While show-goers and consumers have had a look at the group,bikes equipped with the new components were kept behind glass and thosewho who were allowed to play with the shifters were asked to sign a non-disclosure agreement. Few chose to argue the point with SRAM's six-foot-five-inch media rep' Michael Zellman.Now that the embargo is lifted SRAM is touting what calls its new DoubleTapactuation technology.So how does it work?The design of the brake/shift lever is innovative and elegant in its simplicity. The single shift lever is positioned just like the Campagnolo Ergo Power downshift lever behind the brake lever, but it not only downshifts, it upshifts as well.
A small lateral, inward push on the lever releases a pawl from the spring-loaded index gear and upshifts the chain to a smaller cog. A bigger nudge on the lever pushes over the pawl to advance the index gear and downshift the chain to a larger cog.
And, like the Ergo Power downshift lever (and unlike Shimano’s upshift lever), the lever is free to swing straight back to the bar, independent of the brake lever. This makes it possible to hook it under the first index-finger knuckle and pull it back to the handlebar when shifting. Sprinting full-out while pulling hard on the bar is possible while shifting to a higher gear, since only a nudge of that knuckle creates the shift, with nary a hiccup in your sprint.
Riders can also pull the shift lever back to the handlebar and actuateshifts during an aggressive sprint.
The system relies on two engagement pawls and one gear wheel. The engagementpawls work in unison and actually leapfrog each other, pushing each otherinto and out of gears as shifts are actuated. This “leapfrogging” allowsthe single DoubleTap shifter, which sits behind the brake lever, to accomplishall shifts with one simple motion.
The derailleurs, cranks and brakes, and of course cogs and chain, seem very nice, and nobody questions the ability of SRAM and its subsidiaries, Truvativ and Avid, to make these parts well.
