SRAM is rolling out an expansive range of direct-mount chainrings for its 1x11 speed drivetrains.
These CNC-machined aluminum direct-mount rings offer two important benefits over the four-bolt design employed thus far on XX1, XO1 and X1 cranks: increased gearing range and decreased weight.
Curiously, SRAM opted to use two different bolt circle diameters for its three 11-speed mountain groups. The top-tier XX1 group uses a 76mm BCD, allowing riders to go as low as a 28t chainring. However, the 94mm BCD used on X01 and X1 limits the smallest chainring size to 30t.
The new direct-mount X-SYNC rings are compatible with all of SRAM's 1x11 mountain groups
This direct mount chainring option is compatible with XX1, X01 and X1-level cranksets and allows riders to select from a much broader range of tooth counts — everything from a climb-friendly 26t all the way up to a quad-killing 40t ring.
The second important benefit of SRAM’s new direct-mount rings is a reduction in weight. The claimed weight savings of the direct-mount rings ranges from 25-50g, depending on chainring size.
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One downside to this direct-mount approach is that — since the chainring bolts directly onto the crankarm spindle — the chainrings must be offered in dedicated versions for cranksets with 24mm (GXP) and 30mm (BB30) spindles.
The mounting ring for GXP and BB30 cranksets have different diameters, necessitating dedicated rings for each spindle option
