The transmission bargain of the year
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.