The transmission bargain of the year
While Eagle’s 500 per cent range brought the ability to winch up endless climbs to the simplicity and security of a single-ring set-up, initially it came with a high price tag. In one fell swoop though, GX Eagle virtually halved the cost. Significantly this dramatic cost cutting had very little noticeable impact on performance and weight increases were minimal. The greatest price savings and weight gains could be found at the cassette, which used stamped and pinned steel sprockets (with an alloy 50t ring) rather than the intensive CNC machining found on the more expensive X01 and XX1 X-Dome models. Alloy cranks also made a big impact on the affordability, but actually feel stiffer than their carbon cousins. Shifting quality is impressive, if not quite as light-action as X01, and the new jockey wheel design is claimed to prevent jammed chains – the only issue we’ve seen with GX Eagle out in the field, even fitted to numerous test bikes.
This is our long-term review of the SRAM GX Eagle drivetrain. A single-ring 12-speed drivetrain with a 10-50t cassette at an affordable price.
SRAM’s first foray into 12-speed wide-range gears, the SRAM XO1 Eagle groupset, launched last year, brought a gear range that was previously unheard of in the single-ring market. We loved it and gave the maximum marks, but at £977 it was hardly affordable. A couple of months later, however, the everyman’s version was announced, offering the same massive 500 per cent range of gears at less than half the price. Is there a catch? Well I’ve been running it on my bike for the last nine months to try and find out.
The heart of any Eagle groupset is the dinner-plate cassette, which stretches from 10 teeth to a whopping 50 teeth at its lowest. It uses the same 50t alloy ring as its more expensive counterparts, but rather than the expensive machined X-Dome technology found on high-end versions, GX makes do with stamped and riveted sprockets. This saves a lot of money (£170 compared to £302 for the X01 version) but adds 90g in weight.
The rear mech is noticeably bigger than a regular 11-speed GX version and hangs a lot closer to the ground as a result. At 290g it’s only 14g heavier than X01 Eagle and is £92 cheaper, and while it has to make do with cheaper jockey wheel bearings and a heavier steel actuation spring it still has the Type 3 clutch mechanism and handy cage lock for easy wheel removal.
The 12-speed shifter runs on a bushing instead of a bearing, as found in X01, and isn’t quite as smooth or as crisp as a result, but it still has that clunky SRAM solidity to the shifts. Setting the gears up properly is a fickle process and is incredibly sensitive to B-Tension adjustment, but using the supplied guide tool makes it much easier. I also found that cable-routing, and cable quality, make a huge difference to how cleanly and accurately the gears shift. In fact, I’d recommend binning the standard cable and fitting the best quality inner/outer that you can find, and spend some time working out the cleanest cable run that you can. Shift quality and durability will both increase as a result.
Alongside the cassette, most of GX Eagle’s extra weight comes from the crankset. At just £106.99, the cold-forged 7000 series alloy cranks are a third of the price of X01’s carbon units, but you pay a 113g weight penalty as a result. The open pattern on the back of the crank is a mud-magnet, but they do feel plenty stiff enough; more so than the costlier carbon cranks in fact.
The X-Sync 2 chainring is superb. The tooth profile is very complex but has proved both very durable and totally rock solid in terms of chain retention. I don’t run a chain device of any kind and have yet to suffer any chain loss despite the bike being raced, slung down rocky Italian mountains and slogged through a muddy winter. It also runs very quietly and I’ve yet to suffer any chainsuck.
The GXP bottom bracket has been a little less durable; I got seven months’ use from the first one before it needed replacing. Since my bike was kitted out though, SRAM has launched the new SRAM DUB system, which makes for a stronger, lighter crank/BB combo with larger bearings, and GX Eagle is available with a DUB option.
Chain life has been impressive too with very little stretch over the test period. I did manage to snap a chain, but this was completely my fault, as the bike lay filthy in the garage for a week, and it rusted solid.
So, is there a catch? I looked hard but couldn’t find one. Sure, the shifting isn’t quite as crisp as XO1 Eagle, but it’s less than half the price. Sure it weighs a little more than XO1 but it’s less than half the price. Until Shimano come out with a suitable rival, GX Eagle is the cheapest and best way to get a proper wide-range, 12-speed set-up and is the transmission bargain of the year.