If you're a bit of a tech dork like me, you probably get more excited by the latest dream-worthy drivetrain than by the far more common mid-level stuff. It's not our fault, though, with the best tech, the most weight-saving features, and likely a dash of carbon or titanium serving us irresistible bait for easily distracted gearheads everywhere. Despite this, we're all aware that the cost-to-performance ratio doesn't make a lot of sense, especially so if we're talking drivetrains. And given that there are far more mid-level than dentist-worthy bikes on the trails, we should be paying more attention to the drivetrains that come on them.
GX Eagle Expansion Details
• 10-52-tooth Eagle Expansion cassette
• New GX derailleur
• New GX carbon fiber cranks
• Updated graphics
• MSRP: $545 USD (w/ alloy cranks)
• More info: www.sram.com
The latest GX Eagle 12-speed drivetrain retails for $545 USD and includes an 'Eagle Expansion' cassette with a massive 52-tooth large cog that provides a 520-percent range. It's also a big deal for SRAM. A Closer Look at GX Eagle ExpansionCassette
: The GX group's biggest update, literally, is the 52-tooth large cog that's fitted to the back of the cassette. With the same 10-tooth small cog on the opposite end, the new 'Eagle Expansion' cassette has a 520-percent range. That's 20-percentage-points more range than the standard Eagle 10-50-tooth unit, of course, and should provide a stump-pulling low gear. Aside from the pie plate on the back, the rest of the GX cassette remains unchanged. That means it's made using their Full-Pin construction that sees stainless pins hold the first eleven steel cogs together, with the biggest being aluminum.
The Eagle Expansion cassette fits the same XD driver, and weighs 452-grams. That's only 4-grams more than the 10-50 GX cassette (due to the larger cog), and the $215 USD price tag is unchanged. Also, Eagle Expansion is an addition, not a replacement, so SRAM will continue to offer its standard 10-50 Eagle cassettes, but your old GX derailleur won't play nice with the Eagle Expansion. More on that next. Rear Derailleur
: If you're thinking that the old GX derailleur looks a lot like the new GX derailleur with a nicer finish, you're not wrong, but there are a couple of important differences between the two.
First, let's talk about compatibility. The new GX derailleur gets a parallelogram that's a bit longer than what's used on the previous version, an update required so that it'll play nice with that 52-tooth cog. Its predecessor's parallelogram is shorter and while it will sorta work with the Eagle Expansion cassette, SRAM says they'd rather you didn't pair the two.
That means that a 10-52-tooth Eagle Expansion cassette requires the new derailleur, but the new derailleur is backward-compatible with standard 10-50 Eagle gearing.
More changes: SRAM says that they've also increased the amount of chain wrap - how much of the chain is engaged with the cog - by moving the position of the upper offset pulley wheel. This is said to improve both shifting and retention, as does the uprated spring and pivot hardware compared to the previous GX derailleur.
The new GX derailleur weighs 299-grams on my scale, 3-grams more than the old one on the same scale, and the retail price is unchanged at $125 USD.Cranksets
: That's right, there are now two GX cranksets to choose from, with SRAM adding a set of carbon fiber arms that definitely raise GX's Gucci score by a few points.
The GX Eagle Dub carbon fiber crankset is said to weigh 555-grams, or around 65-grams less than the aluminum version, and they cost $275 USD. SRAM says that they're made using very similar tech as you'll find on their pricier carbon offerings, and you'll also get a DUB aluminum spindle and direct-mount chainring.
If you want to stick to metal, the aluminum version is essentially the same as its predecessor, but with a much nicer, shinier finish that sure makes them look like they cost a lot more. But they don’t. They still have the same $135 USD price tag, as well as the same 620-gram weight. Shifter
: Lastly, the GX Eagle 12-speed shifter is also basically the same as before, including the aluminum paddle and Matchmaker compatibility, but it gets the same updated graphics and 'Lunar colorway' that the rest of the group receives. There’s also a single-click e-bike version. The GX Eagle shifter still weighs 122-grams and still costs $45 USD. Why GX Eagle Matters
When you add all of the above together, the new GX Eagle Expansion drivetrain costs $545 USD with the aluminum cranks, which is actually the same as the previous version sold for but now you’re getting a much nicer looking group that essentially weighs the same. More importantly, new GX offers an even wider gearing range; 520-percent trumps 500-percent. And remember that the 10-52 Eagle Expansion cassette doesn't have to be all about getting the lowest possible gear. Instead, you could do the math to compare it to your current cassette and install a larger chainring to keep a consistent low gear and taller high gear. In other words, use your chainring to match the Eagle cassette to your needs.
Zooming out a bit, new GX is likely going to be a big deal for SRAM. In the original-equipment world (the components your bike comes stock with from the factory), it used to be hard to find a bike that didn't
come with GX. Recently Shimano began to challenge them with fresh mid-level groupsets that have performed very well. This new GX group is SRAM's move to retain that market share, and the two companies competing against each other means better drivetrains for all of us.
GX Eagle Expansion showed up only a few days ago, but stay tuned for a full-length review and comparison.