This article originally appeared on BikeRadar
After countless hours of relentless trail riding and racing, SRAM's gold anodised XX1 Eagle group still shines brighter than any other XC gearset.
Highs: Seamless shift across massive range, super efficient feel
Lows: More fragile than X01, 1x11 XX1 is lighter
Buy if: You're not a regular rock knocker and you want the lightest Eagle 12-speed option
The huge 50t 12th cog gives the otherwise one-piece machined steel block a 500 percent gear range. As evidenced by the light amount of wear on the black 50t cog, I've used it rarely, even on the super steep slopes of the Relentless 24hr race at Fort William. For the record, I've not used the 10t smallest gear much, so it's not that I'm running too small a chainring either.
That means the real stand-out feature of XX1 Eagle is the incredible shifting quality even in the filthiest conditions.
Each segment of the chain goes through nearly 40 individual shaping processes for a smooth, quiet transfer between gears. Timing ramps and narrow/wide tooth profiling on the back of both the biggest cogs means it shifts up and down those massive gears better than most much smaller blocks.
XX1 is the best XC transmission available
SRAM's unique X-Horizon, titanium sprung, horizontal rear mech action gets a new smoother and more consistent Type 3 roller bearing chain tensioning clutch and B-Bolt attachment. As a result, the positive, unmissable click lever feel is still as clean and precise as it was six months ago and barely notices filthy chains or convoluted cable routing compared to Shimano.
The shift lever sweep angle and position of the shifter body on the bar clamp (or combined Matchmaker mount) can also be adjusted.
While the cranks aren't the stiffest or lightest, they're a good balance of positive drive without feeling punishing through carbon soled shoes. The double hook X-Sync 2 chainring is a wear reducing, dirt shrugging marvel that stays quiet even at the most extreme chain angles, despite excellent chain security, and you can genuinely feel that extra efficiency under power.
While it's undoubtedly expensive, the massive rainbow coloured, curved plates make the joining link the strongest part of the whole chain rather than the weakest. The rubber protected carbon crank tips and the carbon fibre jockey cage have shrugged off accidental rock strikes and bike drops/crashes too, though X01 is designed to be more damage resistant.
BikeRadar verdict - 4.5/5
"SRAM's palpably efficient, weather ignorant, sweet shifting performance XX1 is the best XC transmission available"
Name: XX1 Eagle
Built by: SRAM
Description: SRAM XX1 Eagle groupset