The new SRAM CX1 chainring uses a rather deep profile that helps offset the teeth inboard but also should improve bending stiffness, too
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First look from the US cyclo-cross national championships
This article first appeared on BikeRadar.com.
SRAM's upcoming CX1 1x11 drivetrain made an appearance in Boulder, Colorado at the 2014 US cyclo-cross national championship on the bikes of Ryan Trebon (Cannondale-Cyclocrossworld.com) and Elle Anderson (California Giant). SRAM still isn't saying much but the bits looks production-ready right now - and they're likely to find a substantial following for next season.
Just as with SRAM's groundbreaking XX1, CX1 is a purpose-built, single-ring drivetrain that uses the company's X-Sync chainring with alternating tooth widths and a clutched rear derailleur pulley cage to ensure chain security without having to run a separate guide. While CX1 should appeal to weight-conscious racers who are strong enough to handle the reduced gearing range, the simplified drivetrain may also offer some performance benefits when racing in muddy conditions.
The rear derailleur design is a close analogue to XX1 but with a shorter cage and a built-in barrel adjuster in place of a friction-reducing pulley. Like XX1, CX1 uses a so-called straight parallelogram geometry instead of a traditional slant parallelogram geometry that SRAM says increases shifting precision on bumpy ground. Chain gap is controlled by an unusually generous offset between the pulley cage pivot and upper pulley.
The new CX1 X-Sync ring mounts to the outer position of what looks to be a standard Red 22 crankset but the teeth are slightly offset toward the centerline of the bike for a more appropriate chainline. We unfortunately weren't able to read the markings on the chain but our guess is that it's the same model as is used on XX1.
Like XX1, CX1's straight parallelogram rear derailleur geometry and hugely offset upper pulley make it a dedicated 1x drivetrain incompatible with multiple chainrings. Riders who are currently on SRAM Red 22 and interested in making the switch, though, will be glad to hear that they likely won't have to buy much to do the conversion: just a rear derailleur, chain, and chainring.
Trebon and Anderson both used standard SRAM PG-1170 cassettes and while their bikes were built with gutted left-hand shift levers, the right-hand levers were standard Red 22 units.
SRAM has pegged the official release of CX1 for later this month so we'll soon have plenty of information to share.
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