Now that cassettes have grown to wider ranges than ever before, the popularity of single-chainring setups has grown exponentially. Running a single front ring means fewer dropped chains, less shifting hassles, more tire clearance and better suspension design opportunities.
Realizing the evolution of dedicated mountain bike drivetrains, SRAM has pulled the wraps of its 11-speed, single chainring group, XX1.
More than just adding a cog to a 10-speed system, XX1 is a ground-up redesign of the whole package, and its components are incompatible with any existing drivetrain. It begins in the front with a specially designed chainring that does not require a chain retention device, and spins out back to a brand-new, clutch-equipped, rear derailleur design and a huge 10-42 cassette that requires a dedicated freehub body.
Machined from a single piece of billet steel, the X-Dome cassette has an “open” interior—giving riders better mud clearance, less weight, cleaner shifting performance and longer component life.
Here it is on the left, pictured next to a standard cassette.
The new XD cassette driver body design lets the drivetrain use a 10 tooth small cog—all while providing better interface across the entire cassette. Wheels with this driver body are available from SRAM and DTSwiss.
Developed for maximum chain control, each tooth’s thickness is precisely CNC-machined to support the chain’s inner and outer links perfectly. Six available chain rings (28-30-32-34-36-38) allow you to tune your gear range to match your terrain, wheel size and riding style. Each chain ring fits a single, universal spider—allowing you to change rings without removing the light-weight carbon crank arm.
- New tooth profile alternates thickness by inner and outer links, providing maximum chain control
- Carbon arms with forged aluminum spider
- CNC-machined rings (28-30-32-34-36-38)
- New spider design allows for easier ring changes
- Wide/narrow Q factor cranks for BB30 and GXP
- Weight: 650 grams with BB (approx.)
With its “horizontal parallelogram” design and pulley offset, the X-Horizon rear derailleur keeps the chain gap constant across all 11 gears, providing fast, precise shifts. By limiting all movement to the horizontal axis, this design is faster, reduces shift force and eliminates ghost shifting. SRAM’s roller bearing clutch technology reduces bounce and chain slap, while the Cage Lock system makes wheel removal and installation easier than ever before.
- Large upper pulley offset automatically adjusts chain gap
- Straight parallelogram design with horizontal movement reduces shift force and improves drivetrain performance
- New silent pulley tooth design
- Weight: 220 grams (approx.)
Shifting is acomplished via a dedicated GripShift unit or a thumb shifter. The GripShifter twists on ball bearings for increased durability and smoothness, with a metal indexing system. The thumb shifter is MatchMaker compatible with other SRAM brakes and accessories.
The system is due in October 2012, with an MSRP of $1,449, and don’t forget to factor in the new rear wheel. Stay tuned for our in-depth review.