It's almost a year to the day since SRAM launched GX Eagle which was, up until this point, its most affordable 12-speed drivetrain available. Thanks to the good old trickledown effect, things have changed, and 12-speed just got (a bit) cheaper.
SRAM's new NX Eagle drivetrain isn't simply a copy and paste job of its pricier counterparts though.
SRAM NX Eagle drivetrain
While the new NX Eagle drivetrain might look almost identical to SRAM's more expensive Eagle components (if you read SRAM's marketing blurb, you'll see it shares many of the same technologies too), there are a number of subtle and not so subtle differences once you delve deeper.The NX Eagle cassette (PG-1230) is really quite different to SRAM's other 12-speed cassettes. That's mainly down to the fact that unlike its XX1, X01 and GX equivalents, it doesn't feature quite as wide a range.
While the more expensive cassettes offer up a 10-50t, 500 percent gear range, the new NX number uses a bigger 11t smallest sprocket (though retains the massive 50t sprocket), which equates to a narrower 454.5 percent range.
And while you lose a bit in terms of gear range, it does mean you won't need SRAM's dedicated XD Driver freehub body to mount the cassette on. That's because it's designed to fit onto a regular splined number (just like the 11-speed 11-42t NX cassette), which means that if you do bite the bullet and upgrade your drivetrain, you'll not need to fork out on a new freehub body on top of all that.
The new NX Eagle crank arms are forged from 6000 series aluminium and are designed to work with SRAM's direct mount X-Sync 2 chainring
In terms of how it's all put together, the new NX cassette differs quite a bit from the GX Eagle cassette, which has 11 stamped steel cogs pinned together with the 50t aluminium cog using high-strength stainless-steel pins. Instead, the NX Eagle cassette has an aluminium spider that has the four largest cogs riveted to it. The remaining smaller, individual cogs are then spaced and pinned together. It's this more cost-effective construction coupled with the fact the biggest 50t cog is steel rather than aluminium, that helps to explain why the NX Eagle cassette is quite a bit weightier.
Unlike the other Eagle cassettes though, SRAM claims the PG-1230 has been designed to withstand the rigours of e-MTB use, so it's likely we'll see NX Eagle feature heavily across the e-bike market in the near future.
On my scales, the NX Eagle cassette weighs 601g while its GX Eagle counterpart tips them at 449g. That said, if you compare the new NX Eagle cassette to an NX 11-speed unit, the difference is a little less at around 60g.
SRAM NX Eagle cranks
The new NX Eagle crank arms are forged from 6000 series aluminium (GX cranks use a different grade aluminium) and are designed to work with SRAM's direct mount X-Sync 2 chainring, which uses three T25 Torx bolts to clamp it firmly to the crank arm.The ring itself is a stamped steel affair, available in 30, 32 and 34t sizes and features SRAM's latest 'shark fin' teeth profiling, which is claimed to improve how load is distributed to the chain, chain retention, mud and trail debris shedding, as well as reduce chain noise.SRAM is offering the NX Eagle cranks in 165, 170 or 175mm lengths. In terms of compatibility, it uses SRAM's new DUB system, complete with 29mm axle diameter, which SRAM says should work with just about all frames out there when used in conjunction with the corresponding DUB bottom bracket.My NX Eagle DUB crankset complete with 32t ring weighed in at 637g, which is only marginally heavier than the GX equivalent at 622g.
SRAM NX Eagle gears
At the rear, taking care of the all-important shifting, sits the new NX Eagle rear derailleur. At 340g it's only 45g heavier than the slightly more expensive GX offering but features much of the same technology. This includes the straight parallelogram design dubbed X-Horizon, the Type 3 Roller Clutch Bearing, which helps keep your chain from flapping around, and Cage Lock, the neat little button that holds the derailleur cage in the extended position to make rear-wheel removal that bit easier.The 14t X-Sync lower pulley wheel is also featured, though I'm assuming this is the revised version, which is set to put pay to some issues other Eagle drivetrains have suffered in the past with seized jockey wheels.Like the GX Eagle shifter, the new NX Eagle shifter isn't as fancy in terms of construction if you compare it to the likes of the X01 or XX1 equivalents and, just like the GX, the larger shifter paddle pivots on a bushing rather than a bearing.
That said, it does feel like a much higher quality unit when comparing it to the 11-speed NX shifter. Interestingly, it's also available as an e-MTB specific option, which only allows single shifts with each push of the lever paddle.
The final piece of the puzzle is the new NX Eagle chain, which uses a solid-pin construction. Like the rest of the NX Eagle components, this works on any SRAM Eagle drivetrain should you need to cut costs when replacing worn out parts.
SRAM NX Eagle first ride impressions
I've had the new NX Eagle drivetrain installed on my Commencal Meta TR V4.2 Origin for just over a month now and clocked up a decent number of miles in a variety of conditions.
As I was replacing the 11-speed NX drivetrain that came as standard on the bike, the new NX Eagle set up slotted on without issue. Not having to replace the freehub to gain an extra gear limits faff and cost, which is a plus in my book.
After one hard ride I did need to re-tighten the cranks' pre-load ring after I felt a little bit of play in them, but since doing that at the side of the trail, things have remained totally problem free.
Aside from adding a touch more tension to the gear cable after it had stretched from new, I've had no issues with the gears skipping or jumping when under power or during rather heavy-handed, last-minute shifts under load. Shifts have remained precise and accurate throughout, including the big jump into the 50t sprocket.
I also felt the shifter action was lighter than that of the 11-speed NX shifter it replaced, and the paddle better shaped. It also feels more sturdy and durable under the thumb.
As my Meta TR weighs in at 15.5kg and a lot of the climbs on my local trails are quite steep, I actually found myself using the big sprocket more than I tend to on lighter bikes with faster rolling tyres that are also equipped with Eagle transmissions. Each shift into the big sprocket felt smooth and precise.
I opted to use a 32t chainring and never struggled finding a gear to suit the terrain I was riding. While I must admit very few of those have been super-fast, pedally trails, I never once felt like I'd run out of gears at higher speeds and still managed to climb some pretty steep pitches even after numerous miles in my legs.
SRAM NX Eagle early verdict
While my ride experience has been positive so far, are there any downsides? You could argue that the cassette is quite heavy (therefore increasing the unsprung mass), though upgrading to the GX equivalent will set you back an extra £70, which is quite a bit for a saving of around 150g.
While the extra weight isn't the end of the world by any means, it's worth taking into consideration should you be thinking about upgrading.
Although it's still early days, all components look to be wearing well too, even after some seriously muddy miles. I'll continue to put the miles in on the NX Eagle drivetrain over the coming months so stay tuned for a full review in the not-too-distant future.
