2017 Sram GX Eagle Drivetrain

On the Trail

I’ve been riding an X01 Eagle group for a few months now, and it’s really, really good. And to be clear, the reason I like it is almost entirely because of the gearing range; on a bike that I would have used a 30-tooth chainring with an 11-speed drivetrain, I can use a 34-tooth chainring and get the same easy gear (actually, slightly easier, as noted above), but I get a significantly higher top gear.

In other words, my climbing gear gets a smidge easier, but at the same time, my descending gears get harder. I can clean the climb yet not spin out on the descent, which is awesome.

After a bit of time on the GX Eagle drivetrain, it’s pretty clear that it does all of those awesome things, but at a lower price.

In terms of shifting performance, there’s barely a difference. The X01 Eagle shifter feels a bit crisper and snappier, but in terms of the drivetrain actually moving the chain between cogs, I can’t say that the GX Eagle kit is clearly inferior. My bike got about 150 grams heavier when I took the X01 Eagle kit off and put the GX Eagle kit on, but that’s pretty tough to notice. The cassette is unsprung weight and those extra grams are marginally noticeable (but even that’s a bit of a stretch).

Really, I don’t have a whole lot to say here. The drivetrain shifts really nicely and it gives me a fantastic gear range. And that right there is everything I want out of a drivetrain.

And most importantly, it does that at a price that’s less than half of an X01 Eagle kit, and that price is entirely competitive with offerings from the competition. Not only does that mean that it’s much more achievable for most people to upgrade their existing bikes, but it also means that more reasonably-priced new bikes are going to come spec’d with a 12-speed drivetrain.

A Somewhat Antiquated Discussion About Front Derailleurs

One of the biggest upsides of the GX Eagle kit is that I don’t have to run a front derailleur. Now, I haven’t run a front derailleur in quite a few years, but there are still plenty of front derailleur defenders out there. And some people will argue that they’re fine with a front derailleur — kind of an “if it’s not broke, why fix it?” sort of argument.

So this isn’t a new discussion, but here’s why I personally don’t like front derailleurs, in order of how much I care:

Frame Selection: Lots of frames don’t even accommodate a front derailleur anymore, so you couldn’t mount one even if you wanted to. And at least part of that is due to clearance issues — making the rear tire and suspension pivots clear a front derailleur means that other sacrifices have to be made. I’d rather have a frame that doesn’t make those sacrifices, and it’s arguably easier to design a suspension linkage around a single ring setup, so there’s that, too.

Dropped Chains: Multiple chainrings mean I can’t run a narrow / wide chainring, and I can’t run a chainguide (yes, 2x guides do exist, but they all suck). I’d drop chains semi-regularly on 2x setups, and even without a guide, I drop them pretty rarely on 1x setups.

Dropper Lever Placement: I am of the opinion that dropper posts are the best bike invention of the past 20 years. And I like my dropper post lever under the bar, in a similar position to a front shifter. But that only works if a front shifter isn’t also occupying that location.

Fewer Things to Go Wrong: 1x drivetrains mean one less shifter, one less derailleur, and one less cable. It’s not that I ever had huge recurring issues with my front shifting, but not having it on the bike means that there’s simply less maintenance and upkeep that I have to worry about.

Less Weight: Having a front derailleur, front shifter, and cable attached to the bike weighs more than not having those things attached to the bike.

Less Cable Clutter and Less Noise. Having fewer cables look better and cleaner than having more cables. And having fewer cables rattling around means that the bike runs quieter.

Downsides

So far, the GX Eagle drivetrain has worked really well for me. So without any shred of doubt, none of these downsides are significant enough to make me not like the drivetrain, and most of them aren’t specific to GX Eagle; I’d say these downsides more-or-less apply to all of the 12-speed drivetrains I’ve ridden.

But even though I don’t see these downsides as deal breakers, they’re still worth noting:

Shifting Adjustment

Compared to a Sram 11-speed drivetrain, the shifting on the Eagle drivetrains (all iterations / levels) is tougher to get dialed. As more gears are packed into (give or take) the same amount of space, the cogs get closer together and the chain gets narrower. As you’d expect from a narrower chain and more cogs that are closer together, getting the derailleur aligned exactly right matters a bit more. I also find that getting the b-tension on the derailleur properly adjusted is fairly critical to shifting performance.

Once everything is setup properly, the drivetrain shifts really well. But if you’re the kind of person whose drivetrain is always a little out of whack, I imagine that the GX Eagle drivetrain (or any Eagle drivetrain, for that matter), has the potential to be a headache. And the need for a fairly precise adjustment also means that if your derailleur hanger is a bit out of alignment or your derailleur has been bent, it may be harder to fudge the adjustment and keep the bike limping along.

Ham-Handed Shifting

While the GX Eagle drivetrain shifts really nicely, I do notice that it’s a bit less tolerant of me thumbing through a bunch of downshifts all at once. I’m mostly attributing this to the narrower spacing between cogs, but I find that if I try to slap through six or more downshifts all in rapid succession (i.e. two full pushes on the downshift lever), and especially if I do it while under moderate load, things don’t go smoothly. To be clear, this isn’t a GX Eagle specific issue; I’d say the same thing about the X01 Eagle. And to be even more clear, this is poor shifting technique, and it isn’t too hard to avoid doing this. But the Eagle drivetrains are just a bit more unwilling to put up with bad shifting technique than most 11- or 10-speed drivetrains.

A Side Note on Chain Strength

As I noted above, more gears means, among other things, a narrower chain. I’ve heard some people express concerns about how the narrower chain isn’t as strong, so I’m here to quash that rumor.

Chain width might have some bearing on chain strength if the chain is taking substantial lateral or torsional forces, but those sort of loads don’t really occur on a bike chain — all of the force is along the length of the chain, and for those forces, width doesn’t matter.

The primary thing that changes when a chain gets narrower is the rollers on each link get skinnier, but that doesn’t have any significant bearing on the chain’s strength. Generally, when bike chains break it’s because of a poorly installed pin. That’s the case on wider 8-, 9-, 10-, and 11-speed chains, and if you decide to not use a master link and try to reinstall a pin on an Eagle chain, it will almost certainly be an issue for you on this chain, too.

Cage Length

To cover the big gearing range, the Eagle derailleurs have a longer derailleur cage. While that potentially means that the derailleur is more prone to damage, personally, I’m less concerned about that, since I don’t tend to shear many derailleurs off. But that longer cage does mean that the derailleur has a tougher time keeping the chain from bouncing around all over the place on rough descents. Fortunately, the Type 3 clutch seems to do a pretty good job of handling that issue.

Increments Between Gears

One complaint about 1x drivetrains is that there are fewer gears, and thus it’s harder to find the “right” gear for a given pedaling cadence. And on its face, this is true — GX Eagle has twelve gear combinations, while a 2×10 setup has twenty possible gear combinations.

Now to be fair, on a 2×10 setup, there’s probably only 15 or 16 gears that are actually usable due to cross-chaining issues, and of those 15 or 16 gears, some of them are redundant, and offer more or less the same gear ratio. But still, a 2x setup (or, gasp, a 3x setup) will usually offer more gear combinations, finer increments between gears, and thus will make it easier to find a gear that allows you to maintain a particular cadence.

And if this was a road bike drivetrain, that might matter. But on a mountain bike, I don’t think it does. Most mountain bike trails aren’t consistent enough in their grade, surface, or straightness to be able to maintain a consistent cadence. Any semi-worthwhile mountain bike trail dips, turns, and alternates between smooth and bumpy with some regularity. Every time the trail changes a bit, that affects the gear I need to be in. And what that means in a practical sense is that, even if I had a drivetrain with perfect increments between the gears (whatever that means), I’m still going to be in the wrong gear most of the time because that’s just the nature of riding a bike on dirt. To put it more directly: I don’t notice that the GX Eagle drivetrain puts me in the wrong gear at the wrong cadence any more than any other drivetrain I’ve ever used, nor do I notice there to be any big, annoying jumps in the gearing between any of the cogs.

Durability and Wear

I don’t have enough time on the GX Eagle kit to make any definitive statements here. My biggest concerns have to do with the aluminum 50-tooth cog on the cassette, and the tooth profile on the Eagle chainring. So I’ll be keeping an eye on those, and I’ll report back as things wear in.

Bottom Line (For Now)

I’m having a pretty hard time finding any real faults with the Sram GX Eagle group; it shifts very nearly as well as the Sram X01 Eagle at less than half the price. And while yes, it weighs more, I’d hardly call it porky — it still weighs a bit less than a Shimano XT drivetrain that has one less cog and a significantly reduced gear range. And more importantly, the GX Eagle group is competitive with XT in terms of price.

The durability of the GX Eagle is the remaining question, and I’ll be spending more time on the GX Eagle to see if it wears out quicker than it should. But I’ve gotta say, GX Eagle has a lot going for it — a huge gear range at a reasonable price — so as long as it’s at least average on the durability front, I’m ready to call it a win.

Long-Term Update

We’ve now put over 1000 miles on the Sram GX Drivetrain, and you can check out our long-term update here.