Remember when SRAM introduced XX1 in 2012? The thought of running a single chainring appealed to many, but the massive cassette and additional gear were enough to outrage the vocal minority. 'Madness!' 'There's no way that chain will stay on.' 'Prove it.' 'I have to change my hub?!' 'Have fun blowing out your knees.'

The concept could have failed then and there. Four years, dozens of XC World Cup and Enduro World Series wins, multiple new 1X drivetrain groups, and countless narrow/wide copies later, it's safe to say 1X is here to stay. But there are still those among us who praise the merits of wider range 2X and 3X systems (yeah, people still run 3X). SRAM's new Eagle 1x12 drivetrains are the company's answer to those holdouts, but also a chance to improve many aspects of the 1X system.

Eagle 1x12 Drivetrain Highlights

  • Available in XX1 and X01 groups
  • Fits existing bikes with XD drivers
  • New 12-speed 10-50 tooth cassette provides 500% gear range (10-12-14-16-18-21-24-28-32-36-42-50 teeth)
  • New direct-mount carbon crankset designs tailored to match your riding needs
  • New chain designed to reduce noise, friction, and wear while being stronger than ever
  • New X-SYNC 2 chainring is quieter and more durable
  • New derailleur with improved Type-3 clutch mechanism and revised B-plate for more secure mount
  • Meets ISO standards
  • Group Weights: XX1 - 1456g, X01 - 1502g including all but bottom bracket (add 60-120g)
  • MSRP: XX1 - $1,417 US, X01 - $1,193 US
  • Available June, 2016

Rise of 1X and the Demise of the Front Derailleur

The truth is that XX1 was originally introduced as a Pro-level drivetrain. It wasn't meant for everyone, but as word about its simplicity, ease of use, quieting effect, and low weight spread, the idea took off in a HUGE way and riders clamored to get in on the action - and not just in mountain biking. Our skinny-wheeled brothers wanted it too.

And while people loved 1X, over the next few years we'd see a movement towards increasingly smaller front chainrings as wheel sizes crept up and Product Managers acknowledged that most of us aren't Pros after all. Many of us need that granny gear. Mountains are still steep and walking sucks.

This all came down to gear range. For some, even with that tiny ring up front, there was never an easy enough gear for those big grunts and going smaller sacrificed speed at the other end of the cassette. SRAM's new Eagle drivetrains address this head on by upping the ante from 420% to 500% of gear range, which is very comparable to the 503% offered by Shimano's current 2x11 systems. And so, with the introduction of a massive 10-50 tooth cassette comes the final blow to the last nail in the front derailleur's coffin. That's one big-ass gold hammer.

SRAM believes in 1X so strongly that they no longer have engineers working on front derailleurs, and there will be no further development in the area in the foreseeable future. SRAM's sales statistics from the past few years show a major decline in bikes equipped with a front derailleur, and an increasing number of bike companies are making frames without any provisions to mount them even if you did want one. Limiting you to a single chainring allows engineers to make better bikes.

At a recent press launch in Italy, Chris Hilton, SRAM's Drivetrain Product Manager, summed up the company's stance: "There are no more excuses for people putting a front derailleur on a mountain bike. They will be extinct in our lifetimes. There will be a day when you say, 'Do you remember when?'"

Then he looked at us straight-faced and said, "Eagles are going to invade the planet, eat front derailleurs alive, and leave them for dead."

We chuckled. It's no secret that we're fans of 1X here at Vital. If we're honest, the question for us was never about the front derailleur, but whether or not Eagle is a better 1X drivetrain. It turns out that's how the project began.

Creating a Better 1X Drivetrain

Make it quieter. Make it smoother. Make it more durable... If only it were that easy.

Since the introduction in 2012, SRAM has manufactured, tested, and ridden hundreds of thousands of 1X drivetrains. They've also learned a lot along the way. Some things worked very well while other details needed improvement.

Raise your hand if your rear derailleur ever loosened itself. Touch your nose with your other hand if you lost a chain. Pick a foot up off the ground if your six-month-old drivetrain sounded like a meat grinder full of walnuts when it was wet outside. Ever bust a chain? Hop around in a circle. Chances are decent that some of you look like fools right now.

SRAM's 1X Eagle drivetrain addresses those issues and more with the introduction of a new chain, revised chainring design, updates to the derailleur, and cranks featuring a better carbon lay up. Best of all it works on normal bikes - if 1x11 will fit your ride, 1x12 will too.

Chain Updates

While it's not likely to get the praise it deserves, the new chain is the biggest reason why Eagle works better. On the inside of the links you'll notice they are smooth looking with none of the sharp edges or chamfers seen on prior SRAM designs. This results in less noise, friction, and wear on the entire system.

Changes to the chain required a new manufacturing process, which now uses progressive stamping to precisely mash metal into perfectly-shaped links over dozens of incremental steps. SRAM says the process was designed with future growth in mind, and we may see updates to other chains as well.

The plates are also flatter, meaning the riveting process can be more consistent for increased strength. It's reportedly SRAM's strongest chain to date. Add in some fancy coatings and the chain's life is extended and friction reduced even further.

Chainring Updates

One of the more obvious updates is the chainring, which features a new X-SYNC 2 tooth profile. The goal behind SRAM's original X-SYNC ring was purely chain retention, so the alternating thick/thin tooth profile was made relatively square. Over time the teeth would wear and create a small "hook," momentarily preventing the chain from releasing as it headed back to the derailleur. This hook was the cause of a lot of noise, especially while climbing in poor weather.

The new design optimizes the load flange and removes some material, which helps avoid creating the hook, reduces wear, improves retention, and helps clear mud better. The longer positive-rake tooth shape is said to last four times longer. That's a massive improvement.

SRAM will only make the Eagle chainring in the direct-mount style at first, and we were told it's the only Eagle component compatible with their 1x11 drivetrains. No 11-speed products will work on Eagle.

Derailleur Updates

Those who raised their hand when we asked if your 11-speed derailleur ever loosened itself will be pleased to learn that SRAM found a solution, and it's not just more Loctite. The problem reared its ugly head on some bikes but not others, and on some it would even tighten itself depending on the suspension kinematics at play. The solution involved the addition of a bushing in the B-plate that allows the derailleur to reliably rotate independently of the mount.

When you rotate the derailleur body backwards it now spins on the bushing and the B-screw remains stationary against the hanger stop. This update also solves the "creaky clutch" issue, which wasn't the clutch after all, but instead two aluminum parts seizing in the B-plate. There's also some forged ridges designed to grab hold of the hanger better. We're told this update will eventually be implemented on SRAM's 11-speed drivetrains as well.

Also new is a Type-3 Roller Bearing Clutch mechanism with a smoother torque curve for a quieter, more consistent operation and feel. The larger 14-tooth lower pulley allows the 10-50 tooth cassette capacity, and yeah, it has a lonnnnng cage. Despite the looks, SRAM claims the ground clearance is about 2mm better than current 2x11 options thanks to the way their straight parallelogram derailleur moves along a horizontal axis. How does it compare to SRAM's 1x11? They didn't say.

A new chain gap tool comes with Eagle to help space the derailleur relative to the biggest cog for the best shifting possible.

Crankset Updates

SRAM will initially offer Eagle in XX1 and X01 groups, and for the first time, they're aiming the two versions at specific users. Ride or race cross-country? XX1 is the lighter of the two groups thanks in large part to a hollow carbon crank design. Prefer a bigger bike for enduro or all-mountain use? The X01 carbon crank is up to the task with a foam core that improves impact resistance and pedal pullout. Just 30 grams separates the two. SRAM previously used the same carbon crank for everything from World Cup pedal fests to Rampage.

Cassette Updates

Ah yes, the big one. Looking closely at the new cassette makes one really appreciate SRAM's incredibly clean X-DOME architecture, which involves machining the 11-cog cluster from chromoly steel and removing all excess material along the way. The cassette has the same gear spacing as the previous 11-speed cassette, but this time they've tacked on an aluminum 50-tooth cog to complete the package. Tooth counts are 10-12-14-16-18-21-24-28-32-36-42-50 with progressively larger 2-2-2-2-3-3-4-4-4-6-8-tooth jumps.

You'll be pleased to learn that the cassette mounts using SRAM's existing XD driver body and doesn't require any additional axle spacing, which was a major design goal. The 50-tooth cog sits just 2mm more inboard than the 42-tooth cog on an 11-speed cassette (it's actually shaped like a satellite dish), and they've ensured the derailleur doesn't come closer to the spokes by placing the derailleur cage in a slightly different position.

New shifting characteristics improve inboard shifts, outboard shifts, and chain retention. We noted X-SYNC-looking teeth on the easiest two cogs which helps keep the chain on while backpedaling.

The cassette weighs in at 355 grams, up from 268 grams for 11-speed XX1. While heavier than their 325 gram pinned 11-speed GX cassette, they're quick to point out that Shimano's 11-speed XTR cassette weighs 331 grams and XT 411 grams.

XX1 Eagle Specs

X01 Eagle Specs

Initial Impressions

SRAM brought us to Massa Marattima, Italy to test the new XX1 and X01 drivetrains over two days of riding. Stepping into the pits for the first time we had to pick our jaws up off the floor after seeing the cassette dwarf the opposing 180mm brake rotor, but over the course of our stay it quickly became "normal," just as the original XX1 cassette did just a few years ago.

In the bike stand, the cable tension adjustment seemed pretty easy to dial in and find the sweet spot. Pushing the shift lever feels similar to the SRAM 1x11 systems you're already familiar with.

As we pedaled out for our first taste of the rocky Italian trails and began climbing, some shifts up were so good we wondered if it had shifted at all. The previous 11-speed system occasionally had a similar feel, but it seemed to occur more often on Eagle. Entering the easiest gear, the system remained quiet with no perceptible grinding through the cranks or by noise.

Following a quick descent we were faced with a steep, unexpected climb, and as we proceeded to mash the lever in search of an easier gear we noted the first instance of a slightly clunky shift up at a slower cadence. The reverse proved to be true as well, with great shifts to harder gears when you're spinning quickly, but a familiar-but-muffled "ka-chunk" when you're lazily slogging along. Make no mistake, it's an improvement over the 11-speed version and far less noticeable.

Just as we found with the recently-introduced OneUp Shark add-on and e*thirteen TRS+ competitors, we found ourselves spending the majority of our time out of the cassette's extremes. The 50-tooth ring was certainly nice to have when things turned steep or the ill effects of jet lag plus too much grappa the night before set in. While it is a large jump up to the big gear, it's the type of shift that has you praising the drivetrain lords for granting you "one more" when you really need it.

On smoother trails and road segments, the ratio jumps were just like you've come to expect from 11-speed versions, and finding the right cadence never seemed to be an issue. This is one advantage of Eagle over the few 11-speed cassettes offering comparable gear ranges, though it comes at the expense of having to shift more gears for broad changes. When dropping into a steep descent after a steep 50-tooth-worthy climb we noticed having to dump what felt like a lot of gears, but as we mentioned, we spent more time in the 42-tooth and smaller cogs which feels identical to SRAM's prior 1x11 system.

This leads us to chainring choice. For riders that feel a 42-tooth rear cog is sufficient for the climbs in your area, consider putting on a larger front chainring to go faster at the other end of the range and stay in the middle of your cassette more often. Mid-range benefits include better efficiency due to less friction, a smoother arc on the chain, and less cross-chaining. Going up four teeth from what you run on SRAM's 1x11 keeps the same low gear, but you end up with a higher high. Going up two teeth gives you some extra range on both ends, making your bike better suited to a wider variety of trails. Tailor the range to your trails and riding style - mashers go big, spinners go small.

For reference, Jerome Clementz (pictured) went to a 38-tooth chainring from a 34. Listen in for a quick interview:

Changing chainring size can have a considerable impact on how a bike rides, though most these days are optimized around something in the 30-34 tooth range. Riders forced to go smaller than this with 1x11 (especially those with 26-tooth rings) may notice some big improvements due to more reasonable anti-squat numbers with the larger chainring that's possible with Eagle. Those exceeding that 34-tooth number may notice a bit more of a squishy pedal feel, but if you're pushing a 38t like Jerome, you're likely a beast already.

As far as range is concerned, we only occasionally used the 50-tooth cog when exhausted and searching for one more, or on truly steep bits that would normally have us standing out of the saddle. There was more gear range available on the bottom end than we could use on Italy's relatively tight trails, but it proved to be useful when racing on the roads back to the hotel.

We had no issues backpedaling in any of the gears, no unexpected skips, the derailleur didn't back out, and it seemed to be quieter through the suspension travel. Despite doing their best to trip us up through some tight squeezes, the rocks never grabbed hold of the derailleur either. All in all, an impressive first showing.

Looking Ahead

SRAM says Eagle will be very popular on mid- to high-end 2017 bike specs, many of which will use Descendant cranks and the X01 group to bring the price point down. Most bikes will see an increase of two teeth on the chainring, providing a higher high and a lower low.

We've seen several frames move to 1X only in the past two years, and with the added range of Eagle we think this trend will continue to grow. With demands for shorter chainstays, better tire clearance, stiffer rear ends, and suspension designs all jostling for real estate, there's only so much space in the bottom bracket area - that's partly why we got the new 148mm Boost axle standard if you recall.

SRAM will continue to produce their 1x11 drivetrains so long as riders are buying them, although if 2017 bike specs are anything to go by, SRAM's 1x11 may disappear faster than the front derailleur (at least at the high end). Will we see more trickle down in 1x12? Likely so, though the market will once again have to speak up with their wallets and let SRAM know what they want.

What's The Bottom Line?

Taken at the most basic level, Eagle can be viewed as the simple addition of a 50-tooth cog to an already-large cassette in an effort to meet wide gear range demands of 2X holdouts. It's much more than that in actuality, however, because SRAM has taken the opportunity to update nearly every component in the group. In the process they've created a better 1X drivetrain with undeniable advantages over their existing systems. Even if you don't personally need the massive cog, there's more speed to be had at the other end of the cassette. With gear range out of the picture, there are now very few arguments left for not switching to a simpler, quieter, and easier-to-use 1X drivetrain.

Eagle drivetrains will be available in June, 2016. Visit www.sram.com for more details.

Update: Read our long term impressions of the SRAM X01 Eagle drivetrain

First Look by Brandon Turman // Photos by Adrian Marcoux and Brandon Turman

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