SRAM's new 10-52t drivetrains out-gear Shimano.

SRAM's new 10-52t drivetrains out-gear Shimano.​

Today, SRAM is introducing three updated component groups. The new Eagle Expansion groups are found at the XX1 and XO1 levels, with a complete redesign of SRAM's affordable GX Eagle 1x12 group. These three Eagle Expansion groups out-gear SRAM's current drivetrains with a two-tooth increase on the largest cog. In addition to this increase in range, the groups also feature updated rear derailleur designs and backward-compatibility with the company's existing 1x12 drivetrains. Let's take a deep dive into the tech behind these new drivetrains.

SRAM Eagle Expansion Groups

The workhorse GX Eagle group gets the largest makeover.

The workhorse GX Eagle group gets the largest makeover.​

As mentioned in the introduction, SRAM is rolling out wider-range 12-speed drivetrains across multiple price points-from the range-topping XX1 Eagle to the budget-minded GX Eagle group. The new GX group gets a complete redesign, while XX1 and XO1 Eagle groups get new colorways along with the wider-range cassettes and updated rear derailleurs.

All these new drivetrains share the new "Eagle Colorsystem" called Lunar Grey that is carried throughout the line to unify the groups. SRAM is keeping the gold and oil slick colors for its chains and cassettes and adding a copper option for riders looking to add a bit of personality to their drivetrains.

SRAM Eagle Expansion Cassette

In addition to the wider range, SRAM is adding this copper color to its gold and oil slick offerings.

In addition to the wider range, SRAM is adding this copper color to its gold and oil slick offerings.​

The changes to SRAM's 12-speed mountain bike groups are evolutionary, rather than revolutionary. The most obvious change is the switch from the 50t to the 52t cog. This cog swap boosts Eagle's range from 500-percent to 520-percent. This two-tooth increase out-gears Shimano's 12-speed drivetrains by one cog.

The smaller 11 cogs on SRAM's 12-speed cassettes remain unchanged. The full tooth count for the Eagle Expansion cassettes is: 10,12,14,16,18,21,24,28,32,36,42,50T.

According to SRAM's Chris Mandell, the company was content with the current steps between gears. "Expanding the range to a 52t is a small step in the design process, allowing us to incrementally improve your experience as we perfect our ideas. If gear step percentage is something that concerns you, our proven 10-50t is still offered," SRAM stated in a FAQ article published in conjunction with this launch.

Related Reading: Frequently asked questions about SRAM's new 12-speed drivetrains

SRAM Expanded Range cassette pricing
  • XX1 Eagle: $449
  • XO1 Eagle: $385
  • GX Eagle: $215

SRAM Eagle Expansion Derailleurs

The new derailleurs are designed to handle the wider range cassettes.

The new derailleurs are designed to handle the wider range cassettes.​

SRAM is launching revised rear derailleurs alongside its wider range cassettes. The new Eagle Expanded Range XX1, XO1, and GX derailleurs are optimized for the larger jump to the 52-tooth cog. The eye-to-eye cage length is the same as previous 12-speed derailleurs, but pulley wheel offset, and the parallelogram design was updated to improve shift performance with 10-52t cassettes.

SRAM Expanded Range derailleur pricing
  • XX1 Eagle: $300
  • XO1 Eagle: $225
  • GX Eagle: $125

SRAM Eagle Drivetrain Compatability

While the new derailleurs are compatible with SRAM's current 10-50t cassettes, the new 10-52t cassettes will only work with the latest Expanded Range derailleurs.

While the new derailleurs are compatible with SRAM's current 10-50t cassettes, the new 10-52t cassettes will only work with the latest Expanded Range derailleurs.​

As stated above, there are subtle but meaningful differences between SRAM's Expanded-Range Eagle derailleurs. As a result, SRAM does not recommend using current cable-actuated 12-speed derailleurs with these new drivetrains. According to SRAM, 12-speed derailleurs designed to shift across 1o-50t cassettes can shift into the 52t cog, but shifting will be labored and less precise.

Thankfully, the AXS-level derailleurs are able to handle the new 10-52t cassettes.

Thankfully, the AXS-level derailleurs are able to handle the new 10-52t cassettes.​

On the plus side, SRAM's electronic XX1 and XO1 Eagle AXS groups are forward-compatible with the new wider-range cassettes. Riders can also use the mechanical Eagle Expansion derailleurs with 10-50t cassettes without issues.

Related Reading: SRAM GX Eagle Expanded Range First Ride Review