SRAM GX Eagle review

First launched back in 2016, SRAM’s Eagle 12-speed drivetrain impressed media and consumers alike thanks to its massive 50t largest cassette sprocket, and quickly established itself as a class leader in the market.

• SRAM gets one up on Shimano with new 52-tooth Eagle cassette
• Shimano Deore goes 12-speed with almost all of the tech of XTR

In fact, back in 2018, we awarded the outgoing 12-speed 50t Eagle 4.5 out of 5 stars, impressed by its reasonable cost and shifting prowess.

During 2020 — after Shimano announced its 12-speed offerings would have 51 teeth cassettes — SRAM upped its maximum Eagle gearing to 52t.

Critics would argue it wanted the upper hand over Shimano, but SRAM says that by increasing the cog size there’s even less chance that you’d need to get off and walk your bike up a climb.

Other updates to the 2021 SRAM GX Eagle drivetrain beyond the redesigned cassette include a derailleur with revised pulley wheel offsets, a shorter cage and larger parallelogram section with new springs and pivot hardware.

And now a new carbon-fibre GX crankset is also available with both the carbon and unchanged alloy versions getting new anodised chainrings.

2021 SRAM GX Eagle 12-speed groupset details

The new cassette is the biggest news here, which uses 123 stainless steel pins to hold the cogs (11 steel and one aluminium) together.

Thanks to the addition of that big 52t cog, the GX Eagle gear range now on offer is a whopping 520 per cent (Shimano’s is 510 per cent for reference).

SRAM has stuck with identical cog sizes (and therefore steps between those gears) on cogs 10-42t, just as the 10-50t cassette has, but the step from the 42t cog up to the 52t now equates to a jump of 23.8 per cent (42t to 50t is a 19 per cent jump).

If that jump sounds a little too much, SRAM still offers the 10-50t cassette.

If you’re thinking of simply buying the new, wider range cassette to work with your original Eagle rear mech, unfortunately SRAM says that the first-generation Eagle derailleurs aren’t compatible. The new rear derailleur will work with both the 10-50t and 10-52t cassettes, though.

But it’s not all about the cassette because SRAM has revamped the rear mech too. The new GX mech gets a revised pulley wheel offset, a shorter cage and lengthened parallelogram along with new spring and pivot hardware, all of which help increase chain wrap which should help boost cassette and chain life as well as improve shift feel.

While I’ve tested the alloy crankset here (which hasn’t structurally changed), there is now a new carbon GX option available too, but both feature SRAM’s new two-tone anodised chainring, a treatment said to better improve durability.

2021 SRAM GX Eagle 12-speed groupset performance

Accurate setup using the new chain gap tool (which you’ll need to set the b-tension screw) is rewarded on the trail with smooth, quiet shifting. It feels crisp and positive too, and I’ve only had to tweak gear cable tension to adjust the indexing to keep things running smoothly.

The bread and butter gears (10-42t) where I spend the majority of my time benefit from the relatively small steps between each cog, making for subtle rather than dramatic changes in cadence. This is a real plus for fast and pedally singletrack.

When you do run out of puff, switching up into that 52t cog does bring with it noticeable relief as well as a change of pace – it truly is a bailout gear. It’s great for slowly winching up steep, prolonged climbs and it’s where I tend to use it most.

That said, I’ve tended to stay in the 42t cog for a little longer than usual (when compared to using the 10-50t cassette), especially on more technical climbs where the 52t spins a little too easily and simply doesn’t offer enough controlled grunt when you really need it.

Shifting into this monster cog is surprisingly smooth and the rear mech manages the move without any signs of struggle or extra force on the shifter required. Dropping back into the 42t is a little more abrupt due to that sizeable jump, and the change in cadence feels a little more pronounced, but not unpleasantly so.

There’s no change at the shifter, but that’s no bad thing. The larger thumb paddle is light enough to operate quickly and the smaller release trigger continues to offer that reassuring ‘snap’ as you drop down through the gears.

2021 SRAM GX Eagle 12-speed groupset bottom line

Overall, I really liked the revised GX Eagle gearing. While that 52t cog might not see quite as much action as the previous 50t, it’s nice to know it’s there for when it’s really needed.

Even after a couple of months, shifting continues to feel smooth and accurate, and it all comes in at a reasonable price.