Revolutionary MTB Drivetrain

Less is more: Learn all about SRAM's new 11-speed transmission
Staff Writer

SRAM has finally released concrete details regarding its much-anticipated XX1 mountain bike drivetrain. The new system—available in October—utilizes a first-ever 11-speed mountain bike cassette with a whopping 10- to 42-tooth range. For reference, just a few years ago, the widest-range cassette available was an 11- to 34-tooth (9-speed) option. So, why so wide? By making the high gear even higher and the low gear even lower, SRAM has eliminated the necessity for multiple front chainings, as well as the front derailleur and shifter that goes along with them.

The result is a lightweight, lean and mean drivetrain option for fast riders looking to go even faster.

And who's it for? At nearly $1,500 for a complete setup (crank, cassette, chain, shifter and all-new X-Horizon rear derailleur), it's clearly for serious riders. And that doesn’t even include the proprietary rear wheel needed to accommodate the ultra-wide rear cassette, with its uber-small high gear. Plan to spend another $1,100-plus for that, or $325 for just the rear hub.

AS SRAM's PR and media manager Tyler Moreland told Bike Magazine, the new group is designed for high-level cross-country and Enduro racers. But what about mere mortals?

“There are definitely riders out there who will love XX1, but those are going to be the people who ride a ton, put in very big miles and are very fit: that percentage is fairly small,” he told Bike. “Again, we’re not touting this as a replacement for X0 or XX [Ed note: SRAM’s standard high-end mountain bike component groups]. This is a standalone 1X group that’s very specific.”

While this initial product offering might not be for everyone, it will undoubtedly garner plenty of attention from the bright-shiny-object-obsessed bike media, and for good reason. After becoming the first company to release a mountain-bike-specific 10-speed cassette option with its XX cross-country race drivetrain back in 2009, we've seen a widespread proliferation of 10-speed drivetrains by both SRAM and its main competitor, Shimano, from the high-end all the way down to entry-level parts groups. With SRAM once again venturing into new tech territory, can we expect the same sort of widespread adoption? Given the need for a proprietary rear hub and the prohibitive cost—probably not anytime soon.

Still, SRAM XX1 represents a major innovative leap forward. Here are some of the new group’s key features.

The main body of the new XX1 “X-DOME” cassette is milled from a single, solid chunk of billet aluminum, and works with a proprietary SRAM rear hub design to offer a miniscule 10-tooth small cog. Its massive 42-tooth big cog has a full six teeth more than the standard 10-speed option dominating the market right now, and it allows the XX1 system enough low-range gearing to drop smaller front climbing gears. The cassette’s 11 speeds (count ‘em, eleven: 10, 12, 14, 16, 18, 21, 24, 28, 32, 36 and 42) offer a whole new way to think about off-road drivetrain design. Target weight: 260 grams.


The new 11-speed-specific front chainrings use what SRAM is calling “X-SYNC” technology, which boils down to individual CNC’d chainring teeth to accommodate the specific contours of inner and outer chain-link plates, respectively. SRAM says the new ring designs provides ultimate chain control, and will be available in six even-numbered size options: 28, 30, 32, 34, 36 and 38.

Rounding out the new XX1 group is an all-new rear derailleur design. While all the major component manufacturers today (Campagnolo, SRAM, Shimano) use some variation of the slant-parallelogram rear derailleur design that SunTour first pioneered back in the 1980s, the “X-HORIZON” derailleur uses a horizontal parallelogram design that SRAM says makes gear changes easier and improves shift performance by better tracking the contour of the cassette. The new unit also uses a one-way roller-bearing clutch to cut down on cage movement and chatter in rough conditions—similar to Shimano’s Shadow-Plus feature. Target weight: 220 grams.