My test setup did not include a full GX Eagle groupset - it included everything but the crank. My Pyga Stage long-term test bike sports SRAM’s GX 11-speed drivetrain with a crank that is compatible with the direct mount GX Eagle chainring.
The obvious benefit of adding 12th and larger 50 tooth cog to the cassette is an increase in the gear range of the whole system. For SRAM's Eagle drivetrain this means a 500% gear range between the largest 50 tooth cog and the smallest 10 tooth cog [(50 ÷ 10) x 100 = 500%].
Most people immediately think about easier climbing but its actually the higher gearing that benefits from being able to fit a large chainring on the front. While I've found 11-speed to suit most riding conditions, there are extremes where additional range would be appreciated. In such cases, this means choosing between comfortable climbing or speed on the flats and downs. This conundrum is solved with the extended range of Eagle's 12-speed system.
In replacing my GX 11-speed drivetrain, I went up one size from a 32 tooth to 34 tooth chainring. This configuration meant that I extended my range in both the highest and lowest gears. The result: more speed when charging and easier climbing when the bonk struck.
A closer look at the components
The GX Eagle range is currently SRAM's entry level into 12-speed drivetrains but what are the real differences between the parts?
The GX Eagle cassette is made up of pressed steel cogs held together by stainless steel pins. The largest 50 tooth cog is made of aluminium. The material costs and manufacturing process are far cheaper than the XX1 and X01 cassettes that are machined out of a solid piece of steel. The result is a cassette that is around 95 grams heavier. The first eleven cogs match the sizes on the familiar 11-speed cassettes (10, 12, 14, 16, 18, 21, 24, 28, 32, 36, 42) with the addition of the larger 12th 50 tooth cog.
Crankset and Chainring
My test system lacked the new GX Eagle crankset which is visually the most noticeable divergence from SRAM’s other single-ring drivetrains. Despite its chunky look, it shaves a few grams off the 11-speed GX crankset.
The chainring features SRAM’s X SYNC 2 tooth profile with the hooked looking tooth at the end. The crank and chainring mounting both use SRAM's direct mount system and are compatible across 11-speed and 12-speed cranks. This means mean that (if you want to save some cash on an upgrade) it is not necessary to buy the new GX Eagle crank. You also do not necessarily need an Eagle chainring, your old 11-speed chainring will do the job.
The GX Eagle derailleur comes with much of the same technology found in the more expensive XX1 and X01 iterations of the drivetrain. But the GX Eagle was initially released with one advantage, SRAM’s version 3.0 clutch system. Another difference is the use of a steel spring instead of a pricey titanium spring.
The GX Eagle chain does not have the gold or black titanium nitride coating found on the XX1 and X01 chains. And solid pins make it marginally heavier than its hollow pin counterparts.
The 12-speed GX Eagle shifter is largely the same as its 11-speed sibling. One feature missing from the lower GX Eagle level is adjustability of the bottom shift lever.
I received the GX Eagle drivetrain about three weeks before taking part in the 7-day Cape Pioneer Trek. This meant that I was able to fit in some solid training with the drivetrain before the hard testing at the race. My experience with the GX Eagle was entirely in a cross-country context, although I have spent some time with the X01 Eagle system on some trail bikes.
I rode for hundreds of kilometers on the GX Eagle groupset without it drawing much of my attention. There was little fuss or fanfare. It simply got on with the job of driving my bike and me forward. Initially, the increased range and a 12th gear provided some novelty but the functional similarity to my previous 11-speed GX drivetrain meant that this sensation soon became normal.
As the smallest 11 cogs on the Eagle cassette mimicked the cog sizes from SRAM's 11-speed cassettes, the jump between gears felt natural with the step up to the 50 tooth cog just another effortless flick of the shifter.
Compared to the 11-speed system that I had replaced on the bike, the move from a 32 chainring to a 34 gave me more range for the flats and downs while still providing some additional range for the climbs. With the improved range, I felt that I could climb any gradient but this did result in a very light front end and I struggled to keep the front wheel down on twisty ascents (more a technique issue than a complaint towards the drivetrain). I was also very happy with the range towards the smaller end of the cassette. At no time did I feel like I was unnecessarily spinning out on the descents.
As a package, the increased range offered by SRAM's Eagle 12-speed was welcome. On my 11-speed setup, I sometimes find myself pushing hopefully on the shifter in the search for an easier gear but with 12-speed, that gear actually exists. Meaning that I had an easy enough gear to keep me rolling through my weakest moments of a 7-day marathon stage race while allowing me to put down power on the fast sections.
There were a few days that I spent several hours riding through sticky mud. And in these conditions, like most drivetrains, the GX Eagle is not infallible. The poor conditions led to a couple of phantom shifts and the odd extra nudge on the shifter to get the chain properly aligned. After a clean and a lube at the end of the stage, however, the system was back to smooth shifting for another day of abuse.
The local SRAM distributor does not supply recommend pricing but a quick look at the local online retailers suggests that a full GX Eagle drivetrain goes for under R8,000 while an upgrade kit can be had for less than R6,000.
In the end
With reliable performance and a far more palatable price than SRAM's other 12-speed offerings, the GX Eagle drivetrain makes a strong case for the upgrade to 12-speed. With weight being the only perceivable disadvantage over the more expensive 12-speed drivetrains, it is going to be hard for the average rider to justify looking further than GX Eagle.