Preview: SRAM’s New XX
|
The recent unveiling of SRAM’s much-anticipated “XX” components group is being met with the collective salivation of gram-counting weight weenies around the world.
With a lightest-case-scenario build (i.e.: picking the 185-gram, 11-32 tooth cassette instead of the 11-36 model in order to save 18 grams), it’s possible to get a complete XX kit to hit the scales at a smidge over 2,200 grams. That’s 400 grams lighter than the previous lightest-in-class Shimano XTR or SRAM X.0.
A whole team of designers and engineers came together to make this new component group happen—they even tapped into SRAM’s RockShox suspension team to integrate a hydraulic lockout into the new MatchMaker X, which can now hold the “XLoc” lockout switch, brake lever and shifter all in one svelte clamp.
The entire XX group is engineered as a system to work with its complementary pieces, and one of the most notable achievements is the new crank, which comes in 39/26, 42/28 and 45/30 gear combinations. The crank arms are modeled on NOIR carbon technology, but SRAM takes the weight savings a step further by threading the chainring bolts right into the crank arms for the smaller ring, and into the chainring itself for the larger ring. It’s a new BCD standard, but hold your groans—these are specially made chainring pairs, engineered to work together. The front shifting doesn’t work even if you swap rings between the three supplied combinations, so forget about aftermarket rings.
|
On its face, it would seem that dropping a granny gear is a simple enough feat. But SRAM engineers took the opportunity to better synch the relative clocking of the front two gears to allow for more windows of opportunity in any given crank rotation to upshift and downshift. There are four upshift and four downshift windows built into the inside of each big chainring.
Without getting too egg-headed, the most notable benefit promised by XX is that those shift windows can be used by the chain in either of what are known as its “latch positions.”
[Tech Dork Note: a chain is made of inner and outer links fastened together in sequence, and therefore it engages with—or “latches to”—any given chainring in one of two positions. The differences between the profiles of those two positions becomes critically important when trying to engineer a “shift feature” that deftly helps lift a moving chain from one chainring up to the next. On a conventional three-ring mountain bike crank’s big ring, regardless of brand, there are two upshift locations for “Latch A,” and two upshift locations for “Latch B.” SRAM says its new XX crank can initiate upshifts in all four of those upshift locations, regardless of “latch.”]
Continued on next page . . .
RSS
TWITTER 
FACEBOOK
YOUTUBE
Add Comment