SRAM MTB NX Eagle Drivetrain 2019 Mountain Bike Review

SRAM MTB NX Eagle Drivetrain 2019

Reviews / Drivetrain

SRAM MTB 166,909

At a Glance

It feels like only yesterday that the Eagle first landed amidst cries of derision that nobody needed 12 gears and that 50t cassettes were ridiculous. At the time the price was pretty ridiculous too, perhaps similar to the latest release of AXS, but over a pretty short period of time, the Eagle has landed at progressively lower price points.

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The time has come for Eagle to hit the 'NX' level and with it, has brought wide range gearing to the masses. No longer the preserve of the pro racer, 12 speed is now accessible, and with the sheer number of bikes coming with NX Eagle onboard, the masses are clearly loving it.

So, for those of you living under a rock, Eagle gives us 12 gears up to 50 teeth and is a single ring only set up. Essentially, you have all the gears you need but with less faff and more reliability in a sweet package. Up till now, Eagle has come as a 10t to 50t spread of gears on a SRAM XD driver, but for the NX, it now sits upon a standard splined freehub body. This is the same sort of body that Shimano cassettes slide onto but by using that system the gearing is 11t to 50t as fitting a 10t wasn't possible. So with all the gears, and availability on a different freehub, it's looking like a winner and the perfect upgrade for many a rider looking to get more gears.

The shifter looks like any other SRAM shifter, but it made mostly of plastic and lacks some of the adjustment on the lever found on the more expensive models. It is clampable on its own or matches up to SRAM levers to keep handlebars clean and simple. The Cassette is a 615g lump of steel, about 250g more than XX1 but the cost saving is clear. The manufacturing is different and uses 4 rings on an aluminium carrier, and the rest are individual, but all this adds to the cost savings.

Cranks are made from 6000 series aluminium rather than 7000 on GX and are a little heavier and with less obvious machined sections removed. It features a plain and simple steel chainring that bolts on with the same X Sync 2 system found throughout the range. The DUB bottom bracket with its 29mm diameter axle is required to make the whole thing fit in your frame, but there are options for all frames, from press fit to standard threaded.

The rear mech looks pretty similar to the GX version but is obviously a little bit cheaper and features a little bit more steel. It features the X Horizon parallelogram movement and has the same Type 3 Roller Clutch found on the other models. The chain has solid pin constriction and provides a cost-effective way of replacing Eagle chains if they break.

It's worth noting that SRAM now talks of the 'Ecosystem', which refers to the compatibility of all Eagle parts with each other, regardless of level. So if you want an NX cassette with an XX1 shifter, then that's totally cool.

On the Trail

Putting a SRAM cassette on a splined freehub body felt wrong, but once I got my head around it the installation is as simple as any other cassette, with the cogs locating in the right place and simply stacked up in order.

The DUB bottom bracket may seem complex with a different axle diameter, but with the appropriate bottom bracket for your frame, it fits easily and cranks are attached, preloaded and tightened easily. The other parts slot into place with ease, the rear mech, shifter and chain going on with no hassle.

A fresh drivetrain is always something to be enjoyed and appreciated. The NX Eagle drivetrain was no different, and once up and running, the shifting felt confident and reliable with no stutters or skips. The shifting experience feels very similar to all the other Eagle systems, and the direct 'click' shifting from SRAM is still present. The only real performance change is that it's not quite as refined, and not quite as quietly confident as the more expensive setups. It's a little more clunky and a touch more agricultural than the top end stuff, but not in a way that's going to ruin your ride. The shifter, although plastic, feels positive and stiff with no discernable flex in the paddles. Get into the spin of things and it's hard to find much to complain about as gears are jumped to and from with speed and commitment, even ramming it up to the largest cog with little regard for the chain proved no issue.

The additional weight isn't obviously noticeable on a big long travel 29er, but on a lighter bike, the increased weight would be a deal breaker for sure. The other 'missing' element is the 10t cog on the cassette, which I had pretty much forgotten about until I came to write this up. The majority of my riding is a winch and plummet style, with steep climbs and even steeper descents. The need to pedal hard downhill is not something I crave, but if you need a 10t, then a GX cassette is the answer, and it saves you a chunk of weight too!

The compatibility of all the Eagle components is a real win for those looking to save some cash and weight in a way that suits them best. The cassette is the one place where this makes the most sense, as the GX is lighter, but the ability to slide an Eagle cassette onto a splined freehub body is not to be overlooked.

Having pedalled through a wet winter, the system has held up admirably. The shifting obviously doesn't improve in the slop and mud, so becomes stiffer and less precise as the cable wears and chain lube is replaced with grit. After a wash and freshen up things run nicely once more, but over time the shifting has lost a bit of its initial precision. After a particularly rough 50km in the mud, the rear mech really didn't like dropping back down through the cassette, but this was mostly due to the cable and a quick swap and clean sorted that out.

The rear mech has stayed straight despite a few knocks and there have been no chain issues at all. The DUB bottom bracket has stayed tight and smooth with no need to nip it up and generally feels like an improvement over the GXP design.


SRAM prove once more why they are a dominant force in drivetrains as they bring Eagle to an even more affordable price point. If you need more gears the NX Eagle now represents an easy access point for a 50t cassette upgrade and offers quality and reliable shifting.

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This review was in Issue 58 of IMB.

For more information visit SRAM MTB


By Ewen Turner
Ewen Turner is a self-confessed bike geek from Kendal in the Lake District of England. He runs a coaching and guiding business up there and has a plethora of knowledge about bikes with an analytical approach to testing. His passion for bicycles is infectious, and he’s a ripper on the trails who prefers to fit his working life around his time on the bike.

Tried this? What did you think?