2017 Sram GX Eagle Drivetrain

SRAM GX Eagle Drivetrain

Total Measured Weight of Groupset: 1,870 grams

Components:

• 10-50 XG-1275 Eagle Cassette
• 12-Speed GX Eagle Rear Derailleur
• GX Eagle Trigger Shifter
• GX Eagle Crankset
• GX Eagle Chain

MSRP: $527

Duration of Test: ~1000 miles (so far)

Mounted to: Santa Cruz Hightower

Test Locations: In and around Whitefish, Montana

Reviewer: 5’9” 150 lbs.

Intro

A year or two ago, Sram declared that the front derailleur was dead. “1x” drivetrains had become increasingly common, and improvements in chain retention, gearing range, and affordability were all ushering in the era of single-ring ubiquity.

But while I’ve been (quite happily) running 1x drivetrains for a while now, there were still some legitimate arguments for keeping two chainrings and a front derailleur, and the most compelling was probably that 11-speed drivetrains didn’t quite have the gear range that some rides required.

But then Sram introduced the XX1 and X01 Eagle drivetrains, which significantly expanded the gearing range available on a 1x setup. And while those drivetrains work extraordinarily well, at over $1200 USD for the less expensive X01 kit, they are also priced at a level that confines them to upper-tier bikes.

Enter the GX Eagle group. It has all of the range of the other Eagle drivetrains, but at a fraction of the cost; MSRP is $527 USD.

So it’s this new GX Eagle group that has the most potential to put the final nail in the coffin of the front derailleur.

Sram released the GX Eagle group a few weeks ago, and we’ve been putting miles on it and getting real-world weights. So it’ll be a little while before we have firm conclusions about durability and longevity, but in the meantime, here are our initial impressions after ten rides.

What’s New & Different

The GX Eagle follows in the footsteps of the top-of-the-line XX1 Eagle drivetrain and the (still very high end) X01 Eagle drivetrains — it’s a 1x drivetrain with a 12-speed cassette cluster. And like the upper-tier Eagle groups, GX Eagle retains the 10-tooth to 50-tooth range on the cassette.

With an X01 Eagle group in one hand and the GX Eagle group in the other, here are the obvious differences between the two:

Derailleur

The X01 Eagle and GX Eagle derailleurs are remarkably similar. The X01 derailleur has nicer hardware, and some aluminum fasteners where the GX Eagle gets steel.

Both the X01 and GX Eagle get the new Type 3 roller bearing clutch, and both have revisions around the mounting bolt and B-set plate to (a) increase durability and (b) resolve the issue of derailleurs loosening themselves, which was pretty common on Sram’s 11-speed drivetrains.

Between the GX and X01 Eagle derailleurs, I don’t see any big functional differences, but the X01 Eagle derailleur weighs a bit less.

Shifter

The X01 Eagle shifter has nicer, metal fittings, whereas the GX Eagle has more plastic. The angle of the X01 Eagle’s downshift lever can be adjusted, whereas the GX Eagle’s levers are in a fixed position.

Internally, they both have Sram’s “Zero Loss” feature, which basically means there’s no slop in the shift lever — any movement of the lever results in movement of the cable. They also both use Sram’s MatchMaker X mounting system, so they play nicely with Sram brakes.

Cassette

The cassette is perhaps the biggest difference between the groups, with the X01 Eagle cassette using Sram’s “X-Dome” technology, which the machining nerd in me thinks is pretty much the coolest thing ever. For the X01 Eagle, the top 11 cogs are machined out of a single piece of steel, then pinned to the aluminum 50-tooth cog.

For the GX Eagle cassette, the top 11 cogs are stamped steel that are pinned together, with the 50-tooth cog still being pinned aluminum:

The real world difference between the X01 Eagle and GX Eagle cassettes is mostly weight savings, although the X01 cassette probably sheds mud a little better.

Cranks

The cranks are another spot with a big and fairly obvious difference. In short, X01 Eagle has carbon cranks, and GX Eagle has aluminum cranks.

The chainrings that are attached to those cranks are a bit different too, with the X01 Eagle ring being a bit more nicely machined, and the GX Eagle ring looking a bit more stamped and less refined.

Both rings, however, have the X-Sync 2 tooth profile, which is both narrow / wide and “wavy” (for lack of a better term). That wavy pattern is supposed to help with chain retention, while also improving how the teeth wear. Older narrow/wide rings were prone to get a bit noisy as they wore, so I’ll be watching this ring to see how it holds up.

But as for the crankset, the real-world difference between the X01 Eagle and GX Eagle is mostly weight. There may be a difference in stiffness, but if there is, it’s not immediately apparent from my time riding each setup.

Chain

The X01 Eagle chain is fully chrome plated (inner and outer links), and the pins are hollow. The GX Eagle only gets chrome plated outer links, and the pins are solid. So there’s a bit of extra weight from the solid pins on the GX Eagle chain, and the X01 chain potentially holds up and shifts a bit better.

All of the Eagle chains are the result of some new manufacturing techniques from Sram that, among other things, means the pins don’t protrude past the links at all (which keeps the chain narrower).

Gear Range

At the risk of stating the obvious, the whole point of the Eagle line of drivetrains is to get a wide gear range with a single front chainring. A bigger gear range means that you get an easier low gear and a harder top gear, all without the fuss of a front derailleur.

Frequently, you’ll see the gear range expressed as a percentage — GX Eagle has a 500% gear range (which you won’t forget, since it’s printed in big letters on the cassette). There’s a 500% difference between the smallest cog (10 teeth) and the biggest cog (50 teeth). Sram 11-speed drivetrains have a 420% gear range, and a Shimano XT 11-46 cassette has a 418% gear range.

Those ranges are all just talking about single chainring setups, but the interesting thing about Eagle drivetrains (including GX Eagle) is that, for the first time, the gear range legitimately competes with a double chainring setup. And the best way to assess that is to look at gear-inch ratios.

Simply put, a gear inch ratio is how many inches the bike moves forward with a single revolution of the cranks in a given gear. So if you take one full pedal stroke, it’s how far the bike is going to travel (without coasting).

For your easy gear, a smaller number means that the gear is easier. You’re traveling less distance for every pedal stroke, which means the gearing is really low. For your hard gear, it’s just the opposite – the higher the number, the farther you’ll go on one pedal stroke, which means that the gear is harder.

Let’s look at four potential drivetrain setups that are realistic examples:

(1) The GX Eagle drivetrain with a 34-tooth chainring, and a 10-50 cassette.
(2) A Sram X1 11-speed drivetrain with a 30-tooth chainring and a 10-42 cassette.
(3) A Shimano XT 11-speed drivetrain with a 32-tooth chainring and an 11-46 cassette
(4) A Shimano XT 10-speed drivetrain with double chainring (24 / 36 tooth) setup and an 11-36 cassette.

For each of those, let’s look at the easiest gear and the hardest gear the drivetrain offers, expressed in gear inches. Remember, a smaller number means the easiest gear is easier, and a bigger number means the hardest gear is harder.

For reference, these numbers are calculated on a 27.5” wheel, with a 2.35” tire:

So what’s the takeaway here? The 10-speed drivetrain with a front derailleur has the easiest gear by a tiny margin — it beats out GX Eagle by .28 inches. But GX Eagle has the hardest gear by a significant amount. And when comparing the GX Eagle drivetrain to the 11-speed drivetrains, it isn’t really even close; GX Eagle has an easier low gear, and a harder high gear by significant margins.

Now all of these configurations can be made easier (or harder) by changing the chainring sizes. By going down to a 32-tooth chainring, the GX Eagle drivetrain would have the easiest gear of the bunch by a fair margin, but the hardest gear wouldn’t quite match the hardest gear of the XT drivetrain with a front derailleur. But the range remains the same, so it just becomes a question of whether you want to scoot that range toward easier gears or harder gears.

Weights

For GX Eagle and X01 Eagle, these are our own measured weights. For Shimano XT, these are stated weights:

The most noteworthy thing here is that GX Eagle is about the same weight as an 11-speed XT group, even though the GX Eagle has an additional cog on the cassette. And that 50-tooth cog has moved past “dinner plate” size, and is now into “serving platter” territory, so the fact that it’s still a smidge lighter is noteworthy.

Price

Shimano XT has always been regarded as a group that offers a lot of performance for the price. And without a doubt, XT is far less expensive than any of the prior Eagle drivetrains, and it’s less expensive than many of the Sram 11-speed drivetrains, too.

But Sram GX Eagle brings some fresh competition to the table.

The prices noted are MSRP. In the real world, most of these components can probably be found for a bit less, and will inevitably go on the occasional sale. For the time being, Shimano XT is probably more likely to be found on sale since it’s not new to the market.

It’s also worth noting that, to use any of the Eagle drivetrains (or most of Sram’s 11-speed drivetrains), you’ll need an XD hub driver. If you’re running a Sram 11-speed drivetrain, chances are you already have an XD driver. If you’re not, you’d need to swap out the driver, which will likely cost somewhere in the neighborhood of $100, depending on the make of your hub.

NEXT: On-Trail Peformance — Pros and Cons