SRAM GX Eagle 1x12 drivetrain £495
Earlier this year, SRAM increased the size of the largest sprocket on their GX, X01 and XX1 Eagle cassettes from 50t to 52t, as well as revamping other key parts of the 12-speed drivetrains. The new GX cassette uses 123 stainless steel pins to hold the cogs (11 steel, one aluminium) together, and now sports a massive 520 per cent gear range. With the exception of the largest sprocket, SRAM have stuck with the same size cogs (and therefore steps between gears) found on their 10-50t cassette. This means there’s now a bigger step between the biggest two sprockets – 42t to 52t is a jump of 23.8 per cent, versus 19 per cent for 42t to 50t.
If you’re hoping to buy the new, wider-range cassette and pair it with your current rear mech, think again, because SRAM say first-generation Eagle derailleurs aren’t compatible (they’ll still offer the 10-50t cassette, which will work with first and second-generation Eagle mechs). In order for the GX Eagle mech to work with the significant changes to the cassette, SRAM have redesigned it, giving it a revised pulley wheel offset, a shorter cage and lengthened parallelogram, along with new spring and pivot hardware.
These changes are designed to increase chain wrap, boosting cassette/chain life, and improve shift feel. While we’ve tested the alloy crankset here (which hasn’t changed structurally), there’s now a new carbon fibre GX option available too.
Accurate set-up using the new chain gap tool (which you’ll need in order to set the B-tension screw) is rewarded with smooth, precise shifting. It feels crisp and positive too, and so far we’ve only had to tweak gear cable tension, to adjust the indexing, to keep things running smoothly.
The bread-and-butter 10-42t gears where we spend the majority of our time benefit from the fact that the steps between each sprocket are relatively small, making for subtle, rather than dramatic, changes in cadence – a real plus for fast-but-pedally singletrack. When you do run out of puff, switching up into that 52t cog does bring noticeable relief as well as a change of pace – it truly is a bailout gear. It’s great for winching up steep, prolonged climbs and that’s where we’ve tended to use it most. That said, we’ve found ourselves staying in the 42t cog for a little longer than we would with the 10-50t cassette, especially on more technical climbs, where the 52t spins a little too easily and 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 any extra force on the shifter. Dropping back into the 42t is a little more abrupt due to that sizable jump, and the change in cadence feels noticeably more pronounced, but not unpleasantly so.
Overall, we really like the revised GX Eagle gearing. While that 52t cog might not see quite as much action as the previous 50t, it’s good to know it’s there for when it’s really needed. Even after a couple of months, shifting continues to feel smooth and accurate too, and it all comes in at a reasonable price. Rob www.zyrofisher.co.uk
Smooth, accurate shifting and a wider-range cassette that’s a real plus for big days in the saddle