Primary use: Mountain bike
Gearing: 1×12
Shifting: Cable actuated

In the SRAM Eagle mountain bike–drivetrain lineup, XO1 sits in the middle, with XX1 above it and GX below it. The 1×12 groupset builds on the benchmark performance of the company’s 1×11 mountain bike groups, but with a bit more range. It can be found on everything from the lightest XC bikes to the burliest enduro bikes. Though GX (the lowest-priced Eagle) offers similar performance at a much lower price, XO1 and XX1 are nearly identical. The only differences are on the scale (XO1 is about 40 grams heavier), on the trail (XO1’s crankset makes it more all-mountain and enduro friendly than XX1) and in your pocket. Oh, and there’s that gold status that comes with XX1, if that’s your thing. SRAM Eagle XO1 can be found on bikes that cost R65,000 or more.

Eagle 1×12 has a Bit More Range Than SRAM’s XX1 1×11 Group

Eagle traces its evolution to SRAM’s XX1 1×11 group that was introduced in the summer of 2012. The basic idea of 1×11 was to eliminate the front derailleur–along with its wonky shifts, mud-catch point, frame-design compromises, and dropped chains–while still providing most of the gear range necessary for satisfying mountain bike riding. Three key features made it work: the 10-42 cassette (420 percent range), a chainring with alternating thick/thin teeth to hold the chain, and a straight-parallelogram rear derailleur with a one-way clutch on the pulley cage. Because a straight-parallelogram derailleur moves only horizontally rather than horizontally and vertically the way a slant parallelogram does (for multiple chainrings), the design helps eliminate ghost shifting from bump-induced derailleur movement. The clutch helps stop pulley-cage bounce, which prevents waves of chain slack from forming.

Eagle 1×12, introduced mid-2016, is simply 1×11 with a bit more range. Eagle’s 10-50 cassette provides 500 percent range, low enough for grunting up steep, high-altitude singletrack and high enough to warp down a fire-road descent. In addition to adding the extra gear, SRAM’s engineers also improved the tooth profile on the chainring to provide even more robust chain retention (the chainring is compatible with SRAM’s 1×11 drivetrain).

XO1 Eagle Group Details

Cassette: The cassette is offered in only a 10-50 combination. But with multiple chainring options available—30-, 32-, 34-, 36-, 38-, and 40-tooth (round); 32-, 34-, 36-, and 38-tooth (oval)—a rider can adjust overall gear ratio.

Cranks: XX1 Eagle cranks are offered in two formats: SRAM’s familiar 24mm steel GXP axle and DUB, a 28.99mm-diameter aluminum axle the company claims is lighter and stiffer than GXP and designed to be compatible with all major bottom bracket shell formats. And about that crankset being more all-mountain and enduro friendly. It’s because XO1’s carbon-composite, foam-core cranksets are more impact resistant than XX1’s carbon-composite, hollow-arm cranksets.

Shifters: Most XO1 Eagle–equipped bikes will come with SRAM’s familiar trigger shifter, but a compatible twist shifter (called Grip Shift) is available as well.

If you ride XO1 Eagle back to back with XX1 Eagle, you won’t notice a performance difference. Both groups feel, function, and perform identically – which is to say, very well. SRAM’s 1×12 groups – X01 and XX1 Eagle in particular – are the current benchmark for mountain bike drivetrains. Shifting is fast and precise, the drivetrain is stable, with no ghost shifts or thrown chains, and there’s a gear range for every situation. Overall, XO1 Eagle is light, simple, durable, and more than capable in the crappiest of conditions.

READ MORE ON: gear SRAM XO1 Eagle