Review -

SRAM X01 Eagle Review – The new Standard of Shifting?

When SRAM dropped the Eagle drivetrain last year, the world of mountain biking came to a standstill. But amazement walked down the aisle with skepticism – was this 1x drivetrain going to stand the test of time? 10 months down, it’s time for the SRAM X01 Eagle to meet the jury.

After 10 months on the trails, it’s time for the SRAM X01 Eagle to meet the jury.

Last year we bid farewell to a good friend of ours (fortunately, there were no tears involved). The friend in question – the front mech – had been in decline for a while, going from three to two chainrings in a matter of years. When SRAM launched the XX1 back in 2012, this 11-speed transmission heralded a new era and the advantages were immense: lighter, more intuitive, faster, quieter shifting and the list went on. The 1x drivetrain made brand new frame designs a reality, enabling better geometry, increased rigidity and more tire clearance. But it also had its flaws and 1×11 wasn’t perfect. But then the Eagle landed in 2016 and SRAM declared that their shifting technology had now been invested in the best drivetrain in history, one that was capable of eliminating all those previous 1×11 issues. So, were SRAM all hype or was there truth in their claims?

The SRAM X01 Eagle in Detail

Much like the SRAM XX1, X01, X1, G1 and now the NX, the SRAM X01 Eagle drivetrain also consists of five parts: the cassette, cranks, derailleur, shifter, chain. According to SRAM, each part has been crafted to work in unison; the intention is that they’re all used as one system. Each part has undergone major redevelopments, seeing the cassette get bigger, the derailleur adopt a longer cage, better clutch damping, extra teeth on the jockey wheel, a new tooth profile and a new interface between the crank and the chainring, and a thinner (but no less robust) chain. We’ll spare the intricacies, but suffice to say that SRAM went into meticulous detail in order to weasel out every possible performance gain, running through countless prototypes before settling on the Eagle as it is.

The enormous 10–50 tooth cassette is at the heart of the Eagle.

For most people, the actual weight of the SRAM Eagle is irrelevant. If a product is good enough, most in the industry will overlook what it weighs. Adding or shaving off 100 grams to your bike quite frankly isn’t a crisis. But admittedly grams can add up quickly, yet what determines how much you have on the trails isn’t 12 kg or 13 kg. Suffice to say, the SRAM X01 Eagle is light. It’s around 50 g heavier than the XX1 but it’s significantly lighter than a 2x gearing set-up. Unfortunately, it’s also expensive at around € 1,300 for the drivetrain.

The Advantages of the SRAM X01 Eagle

Forget those extra grams on the scales and concentrate on the advantages of this 12-speed drivetrain. For many, the huge 500% gear range (10-50 tooth) is the major selling point. But it goes way beyond that – and the team at SRAM are pretty vocal about how many improvements they’ve made to the 11-speed cassette with the Eagle. People complained about high levels of wear and tear on the front chainring, which is now a thing of the past, along with noisy shifting in the mud, and bolts loosening periodically. Shifting happens with speed and precision. Although naturally, this means getting the correct set-up dialed.

Spot the rainbow-coloured chainlock.
The new tooth profile is reputed to lead to better chain retention.

Setting up the SRAM X01 Eagle

Unlike mounting and adjusting a front derailleur, the SRAM X01 Eagle basically has a plug-and-play set-up. Screw on the derailleur, tighten the cranks, mount the cassette, tighten the trigger and shorten the chain. Then just thread the gear cable and align the rear mech. No sorcery here. There’s one screw that demands your attention though: the B-Tension screw. This is essentially what SRAM have developed in pursuit of the ultimate tension between the top jockey wheel to the cassette when you’re in the easiest gear – and in sag. It’s definitely wise to take your time in this part of the process, and be prepared to tweak it a little afterwards.

This little red tool is key to setting the chain gap. Note: do it while in sag.

The Gearing on the SRAM X01 Eagle

SRAM have managed to get the virtually the same gear range – namely 500 % – that you’d get with a 2x set-up, but condensed it onto one cassette. Its tooth count looks like this: 10-12-14-16-18-21-24-28-32-36-42-50, which translates to the following gear steps: 2-2-2-2-2-3-3-4-4-4-6-8. If all you see is these numbers though, then you’d be forgiven for thinking the steps between the gears might be getting too big, but you’ve got look at this from a percentage perspective on the sprockets. Across the whole gear range the shifts stay constant between 15 and 18%. From the 12t to the 36t cog, you’ve actually got the old 10-speed cassette sitting in there.

The gear range is brilliant and the gear steps are bang on!

The SRAM X01 Eagle on the Trail

A drivetrain has one job: firstly, shift when needed, and always proffer the right gearing. The SRAM X01 Eagle fulfills this purpose sublimely. It’s virtually silent while shifting, and even shifts with surgical precision when you’re grinding your way up the steepest climb and almost at a standstill. Its 500 % gear range seriously covers the whole spectrum, meaning you’re sorted for gearing whether you’re tearing up the flat or faced with a momentous gradient. If you choose an optimal chainring at the front, you’ll get 2 extra gears compared to the 11-speed shifter: one easier and one harder. On our long-term test bike, the Santa Cruz Hightower 29er, we went for a 32t chainring (we used to ride it with a 30t one), and this proved to be a great choice. The steps between the cogs were bang on too.

The chain stayed in place no matter how burly the trails got.

When we kicked off this long-term test, we didn’t really expect much use from the giant 50t sprocket (and yeah, some test riders are still unconvinced), but if you’re heading out for a mega mountain epic, it’s definitely not unwelcome when you get close to bonking. There’s another advantage as well, namely when you’re pedaling backwards in the easiest gear; 11-speed drivetrains usually throw off the chain, but the Eagle kept a firm stance. In fact, we can’t recall a single chain drop in the whole of the past 10 months. The longer cage was another pre-test concern, and admittedly it is a bit more exposed, however, compare its position to what you’d find on a 26″ mountain bike and you’ll be worry-free.

Purely superficial complaints when it comes to wear and tear.

The Durability of the SRAM X01 Eagle

This point is easily wrapped up. We’ve covered around 1,000 kilometers using the SRAM Eagle and it has come out shining (well, almost). We got off to a bad start with a broken derailleur bolt but it was replaced immediately and SRAM have stated that they’ve now improved this component. Ridden on a fleet of test bikes, the drivetrain system has been running faultlessly, with the cassette proving to be exceptionally robust (which, to be honest, shouldn’t be a surprise considering the price tag). And to all those who cried about the inevitability of snapped chains due to the narrower design we haven’t snapped one yet.

Our Thoughts on the SRAM X01 Eagle

The SRAM X01 Eagle landed and hit the ground running as the best drivetrain we’ve ever ridden. It shifts with precision, smoothness, no noise and has proven steadfast and reliable. Now that’d be enough for us, but then add in the gear range. For us, this certifies that 1x is for everyone. It is beyond budget for some but we’re confident that SRAM will make it more affordable very soon.


  • Great, smooth shifting
  • Huge gear range
  • Durable


  • Requires precision, and the B-Tension has to be perfectly tuned

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