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The Technology


Cassette

In order to fit in the extra 12th gear, an entirely new cassette had to be built with the cogs spaced closer together than its 11 speed counterparts. The first 11 gears mirror SRAM's 11 speed cassette (10-12-14-16-18-21-24-28-32-36-42) which means an easy learning curve for those already familiar with SRAM's 1x drivetrain, there is simply a bigger cog at the end of the range. The dedicated 12-speed spacing makes compatibility an issue with the crank being the only part that can be carried over from SRAM's 11-speed system.


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With the addition of the 50-tooth granny gear, riders will need to jump up a chainring size or two to take full advantage of the cassettes 500% range. SRAM Eagle with a 36-tooth chainring will give you the same top-end and low range of a 39/26 2x drivetrain running an 11-36 cassette. The Eagle XX1 cassette weighs a claimed 355g (87 grams more than 11-speed XX1) and is constructed using SRAM's X-Dome technique, where nine of the cogs are machined out of a single piece of steel billet. Two of the three remaining cogs are made separately from steel, and the final 50-tooth cog is aluminium.

Chainring


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SRAM claim that the new X-Sync 2 chainring tooth profile lasts much longer than than existing X-Sync rings and that the new tooth shape has more mud clearance. Cutouts in the material also prevent chain suck as the teeth on the ring wear. In addition, the new X-Sync 2 distributes load over more teeth to reduce wear and the trailing edge has been removed to quieten release at the bottom of the stroke. The chainrings are direct-mount only and available in even number sizes from 30 to 38.

Derailleur


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The new 12-speed derailleurs feature a larger 14-tooth X-Sync lower pulley (two teeth larger than its 11-speed sibling) to accommodate shifting across the extended range and sport a quieter, smoother Type-3 roller bearing clutch mechanism. The B-knuckle (the portion of the derailleur that is threaded onto the hanger) has been tweaked to help keep the mounting bolt from unthreading itself. SRAM have also added a bushing around the mounting bolt, allowing the derailleur to pivot forwards and back without bringing the bolt with it. The XX1 Eagle derailleur gets a carbon fibre cage and a titanium spring, allowing it to weigh in 12 grams lighter than the aluminium cage on Eagle X01.

Further updates see the Cage Lock button relocated away from the front of the derailleur to better protect it from impacts

Shifter

The shifters have been updated to include a 12th gear and improved to enhance trigger feel, precision and durability. The position-adjustable shift lever and the top cover are made from carbon fibre to reduce weight. There is also a Grip Shift option for those who prefer them over a more traditional trigger shifter.

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Chain

The Eagle chain links have a smooth radius, with no sharp edges or chamfers, which yield a significant reduction in noise, friction and wear on chainrings and cassette cogs. This design also allows for a flatter plate, which means more consistent chain riveting and greater overall strength. The plates have smooth, rounded edges, as well as chamfers at the rivet holes, so the rivets sit flush with the outer plates. Hard Chrome technology extends the chain’s optimal performance life and a Titanium Nitride coating decreases corrosion and further reduces friction.

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SRAM claim that the Eagle chain is the quietest, strongest and most wear-resistant chain in the world and that its unique design also provides significantly improved wear resistance on Eagle cassettes and rings. The chains are made in SRAM's own factory in Portugal giving them full control over quality. In their quest to design a quieter, longer lasting drivetrain, SRAM built all-new machines and utilized new processes in the development of the Eagle chain. It is not just narrower.

The Eagle Power Lock chain connector was also redesigned with Flowlink technology that provides better chain-guiding and increased longevity. Flowlink is marketing talk for ultra-smooth inner-plates that are completely devoid of square edges, resulting in a chain that engages the cassette and chainring with far less friction, for quieter performance and better wear life. The design allows a narrower overall profile that can withstand greater angles, and also allows for a flatter outer-plate, which means more consistent chain riveting and enhanced overall strength.

Crankset

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The new Eagle XX1 crankset features a special hollow internal architecture, combined with SRAM's proprietary Carbon Tuned lay-up, that has enabled them to build a crankset that is said to be the lightest, stiffest and strongest on the market. This hollowed-out design however limits it to cross-country and trail duty only.

On the Trail


In preparation for my time on Eagle, I took my 1x11 equipped bike out for a couple of rides as I felt it would give me a good point of reference to the changes in design and extended range of the Eagle system.

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Knowing that the biggest jump in number of teeth was from the 42T to the new 50T Granny, I shifted between these cogs under varied circumstances, but each time the chain slotted into place without any drama or a feeling that it was a stretch for the drivetrain. Overall, the shifting experience was "positive" with no ghost-shifting or delay in engaging when shifting up or down.

However the first thing I noticed when I hit the trails on the Eagle equipped Niner R.I.P. 9 was just how quiet and smooth the drivetrain is. There is a distinct lack of drivetrain "noise" especially when in the upper extremities of the cassette. So much so that I went back to our launch article just to double check what was done to achieve this.

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The biggest on trail benefit was the fact that the test bike could run a 36T chainring compared to my own bike's 32T. As mentioned, above, this gave me the same top end range I would have had on a 39/26 double chainring configuration. This meant there was no comical spinning out of gears when things turned downhill. I could comfortably put in a couple of pedal strokes when needed even with speeds in excess of 45km/h. At this stage my 32T 11-speed would have been reduced to freewheeling.

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Range comparison between a 10 speed drivetrain running 39/26T chainrings with a 11-36T cassette and 12 speed Eagle using a 36T chainring with it's 10-50 cassette.

If however you are after the extra breathing space when climbing, chances are you will still be able to jump up one chairing size and score at both ends of the spectrum. The table below shows running a 34T-50T combination will give you a lower granny than running 30T-42T. In fact, you would have to go down to 28T-42T to beat it, without the drawbacks that would come with running 28T-10T on the flats and downhills.

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12 Speed Eagle compared to an 11 speed drivetrain showing how the 50T granny gear impacts on chainring size selection.