Today's mountain bikes are more capable than ever before, especially in the most common, "daily driver" trail bike genre. Yet, with constant growth of newly formed resort bike parks, plus the ability for downhill racing fans to view the World Cup events live online, the niche, yet technologically advanced, segment of downhill mountain biking has more worldwide participation and attention than ever before. Additionally, with several brands offering reasonably priced, competition-worthy complete downhill bikes the barrier for entry is significantly lower.
It's been about 18 months since SRAM introduced its GX DH drivetrain component group, and its main objectives revolve around durability and dependability. If you're wondering what a DH-specific drivetrain entails, imagine a sports car with a manual transmission, but it only has third through sixth gears, no super-low gears for going uphill. Having fewer usable cogs in the downhill application gives the rider a faster transition from their starting cog to the highest desired cog.
SRAM's GX DH seven-speed configuration was developed as a more affordable version of the top-shelf, race-oriented X01 DH seven-speed group. The GX DH group promises effortless and precise shifting in a dedicated gravity oriented one-by drivetrain setup at a fraction of the X01 DH group price. SRAM recommends its Descendant crank and PC-1130 11-speed chain for the GX DH group, but technically it consists only of the trigger shifter ($43, 122 grams), rear derailleur ($104, 263 grams), and the seven-speed DH-specific cassette ($30, 224 grams) for a total claimed weight of 609 grams (1.34 pounds) and a total investment of $177. Comparatively, the spendier X01 DH group including a shifter, derailleur, and cassette will set you back $700 with a total weight savings of 91 grams (3.2 ounces). A closer look reveals a hefty chunk of the price and weight difference between the two groups lives at the cassette. The $30 GX DH cassette (model name PG-720) weighs 88 grams more than the claimed weight of the $284, one-piece X01 DH cassette (model name XG-795 Mini Block X-Dome), which is specifically designed for SRAM's threaded XD driver body.
GX DH GROUP DETAILS
A lot of downhill bikes play second fiddle to their owners' trail bikes, therefore DH machines often don't warrant annual overhauls and upgrades to the latest standards and trends. Conveniently, the GX DH seven-speed cassette mounts to the ubiquitous standard Shimano/SRAM splined freehub body. The cassette's gear range includes 11, 13, 15, 17, 19, 22 and 25-tooth cogs.
The GX DH derailleur features SRAM's X-Horizon design developed to reduce shift force, ghost shifting, and cage slap. SRAM says the GX DH drivetrain is designed around 11-speed chains.
It's worth mentioning the GX DH trigger doesn't include a handlebar clamp. So, if this groupset is on your radar, you better cash out another 15 bucks worth of Bitcoin so you can actually mount the shifter on your bike. Also, the GX shifter does not feature SRAM's ZeroLoss system, which is intended to reduce subtle, unwanted movement or "play" at the triggers.
I swapped out a short-cage SRAM X9 rear derailleur and 10-speed mid-level SRAM road cassette for the seven-speed GX DH setup. Having been on the same DH frame for a couple of seasons, and coming off of a SRAM drivetrain, I didn't expect huge differences in performance. But on the first ride with the GX DH group I immediately thought, "What's that noise?" Turns out, it was the uninterrupted sound of my tires hooking up on the dirt. The GX DH derailleur does a great job of reducing unwanted chain slap and drivetrain wonkiness to deliver a near-silent ride.
As a longtime fan of SRAM triggers, I anticipated the smooth performance I've grown to expect. Although nitpicky, I didn't find the GX trigger action as crisp as its higher-end siblings. Yet, the shifts were precise, and impressively effortless as the derailleur danced up and down the cassette with minimal lever input.
Along with the GX DH's impressive on-trail performance, it's also fully compatible with SRAM's X01 DH groupset, making the GX version an excellent backup drivetrain choice for racers. After a year aboard the GX DH group, its reliable, quiet performance, plus the affordable price makes it a no-brainer for weekend warriors and serious downhillers alike.