SRAM follows up the release of its impressive XX, XX SL, and X0 T-Type drivetrains with a more affordable GX offering that brings the same secure connection, robust construction and simple set-up to a much lower price.

• Check out our buyer’s guide to the best MTB drivetrains and groupsets

Need to know

• Cheapest spec level of the all-new SRAM Transmission wireless drivetrain
• Hangerless interface allows a ‘Full Mount’ fixing for the rear derailleur for increased durability
• Next level shifting precision under load
• Promises user-friendly and quick installation
• Rebuildable rear derailleur with replaceable hardware
• Set-up and personalisation with SRAM’s AXS app
• Groupset price includes rear mech, shifter, cranks, cassette, chain, battery and charger
• Approx £200 premium over previous generation GX AXS groupset

Trickle down tech

SRAM is a brand that doesn’t seem to stand still for very long. Always innovating and refining, it dropped the potentially game-changing Eagle Transmission in the premium X0, XX and XX SL spec levels this spring. If you’ve had an eye on any MTB media over the last few months you won’t have missed the coverage – with brand ambassadors and pro riders praising its durability, reliability and ease of set-up. There was no shortage of hype, and yes, we admit to standing on the back end of our bikes to impress the sceptical, but so far, our experience has backed up the fanfare.

As with most of SRAM’s developments, the tech eventually trickles down the range, and sooner than we would have anticipated, it’s GX, the brand’s workhorse spec level, that benefits from this new thinking. If you’ve not watched MBR’s launch video on SRAM’s Transmission (we’ve embedded it below) we’ll run through its defining features now, before making a deep dive into the specifics of the GX level components.

Total integration

The latest Eagle Transmission capitalises on SRAM’s ‘system mindset’, taking its proven AXS technology and applying it to a complete rethink of how the rear derailleur is attached to the frame, and how it interacts with the cassette sprockets and chainring. It’s built around one constant focus across all bikes – the centre of the rear wheel axle. Not long ago SRAM introduced its Universal Derailleur Hanger (UDH) to standardise the rear end interface of the bike, bypassing the hundreds of different hanger models out there and creating a version that’s more robust and better aligned. Removing the UDH from the frame gives a hangerless interface, and when paired with the security of the bolt-thru axle, provides the fixing point for the robust and secure ‘Full Mount’ T-Type derailleur – the linchpin of this new drivetrain. Every other component has been reworked though: the cassette, chain, and chainring are new and all are interdependent for the Eagle Transmission to function correctly.

As with the cable-operated Eagle drivetrains, you can mix components from different tiers as long as you stay within SRAM’s ‘ecosystem’. So although GX is the cheapest in the Eagle Transmission line up – and misses out on a few neat features – you can cherry-pick components from the higher spec X0 and XX levels. Just be aware that some of the lighter weight cross-country focussed XX SL components are not rated for E-bikes.

GX rear derailleur £430

Weight: 468g

Where the boutique level X0, XX and XX SL T-Type derailleurs all use a consistent blueprint, this GX model employs slightly different architecture and a reconfigured gearbox. The design ethos remains the same, with robustness and the ability to rebuild it and replace hardware being top priorities. The key structural difference on this GX model is the placement of the battery, which is now neatly tucked in at the top of the derailleur’s body (rather than the rear) and protected further by the frame’s dropout.

Some concessions to cost have been made with this mech, with a steel backing plate on the ‘tool free’ cage assembly – which should boost durability. The Magic Wheels (which still spin even with debris caught in them) seen on the premium XX T-Type derailleurs are absent here, but you can upgrade to them, with or without a higher spec cage. 

Set up protocol and pairing to the shifter pod is identical to the higher spec models, as is the angled mech cage which points towards the chainring regardless of which gear you’re in. There are replaceable skid plates too, so you can retain the derailleur’s sharp looks.

Cassette and chain £270/£55

Weight: 445g cassette, 285g chain

Although the T-Type 12-speed cassettes use an all-new design and are specific to the Transmission drivetrain, thankfully there’s no new hub fitment or standard. If you have a rear hub with Boost spacing and a SRAM XD driver body you’re good to go. 

At 445g this XS-1275 cassette is noticeably heavier than the higher spec T-Type options, but it is a hair lighter (9g) than a standard GX level Eagle cassette. It uses both PinDome and Mini-Cluster construction, rather than the costlier X-Dome technology.

SRAM has stuck with a 10-52t range for T-Type cassettes (with no other options), but has now evened out the steps between the ratios, with larger 38t and 44t sprockets replacing the regular Eagle’s 36t and 42t for the second and third gears.

As with the cassette, the new GX level T-Type chain is nickel plated to increase durability and reduce noise. It uses SRAM’s flattop design – first seen on the brand’s road drivetrains – and solid pins, and it’s rated to deal with the increased torque on e-bikes.

Getting the orientation and the length of the chain is an important part of the set-up procedure and is not a step to skip. The AXS app will give you the correct number of links for your specific bike model but this is also dependent on chainring size and chainstay length, so if you tweak these down the line you’ll need to readdress the chain’s length.

Cranks, chainring and bash guard £215

Weight: 661g, 82g bashguard x2

This all-new GX Transmission is spot on for use on e-bikess as well as regular trail and enduro bikes, so it’s no surprise that SRAM has developed cranks and chainrings for both applications. Unless bought as a groupset, the e-bike cranks and chainrings are priced separately, with options available to fit Bosch, Brose, and Shimano motors and crank lengths from 160mm upwards. There’s even an option to add a ‘Gap Cap’ for a slick, integrated look.

We have the regular cranks on test, which use SRAM’s DUB axle standard, but with an all-new shape and SRAM’s Dark Polar slate grey finish which matches the rear derailleur. The aluminium T-Type chainring is available in 30t, 32t or 34t and uses an eight-bolt fitting that’s unique to the Eagle Transmission drivetrains. Also new are the bolt-on bash guards, which attach via two T25 Torx bolts and a back plate, clamping through dedicated gaps in the chainring. They’re lightweight, easy to fit, and an option not a necessity.

AXS Pod controller £160

Weight: 51g

This AXS shifter pod is another component that’s had a makeover, and although launched in tandem with the Transmission ecosystem, is compatible with SRAM’s regular Eagle AXS drivetrains.

With a lower weight, improved ergonomics and a choice of mounting systems – a discrete clamp for SRAM’s brake levers or a minimalist independent mount – it’s a much cleaner looking shifter when compared to the older design. It’s offered in two models that can be used on any of the Eagle Transmission drivetrains, with the deluxe version supplied with both convex and concave pad options for the shifter buttons.

The controller pod can be adjusted independently of the mount’s rotation, allowing some real fine tuning of the position, which, as I found out when I got some riding timing in, was key to avoiding any miss-shifts.

SRAM GX and GX AXS Transmission actual weights

	GX Mechanical	GX AXS Transmission
Rear derailleur and hardware	299g	468g
Shifter and bracket	173g	51g
Cranks and chainring (No BB)	624g	661g
Cassette	454g	445g
Chain	251g	285g
Cable, housing and hanger	96g	N/A
Battery	N/A	28g
Bashguards (2)	N/A	82g
System weight	1897g	2020g

SRAM GX Transmission prices

	GX Eagle AXS T-type	GX Eagle AXS (old)*
Derailleur	£430	£361
Shifter	£160	£147
Cranks	£215	£134
Cassette	£270	£217
Chain	£55	£32
Chainring	£43	£40
Complete drivetrain	£1,180	£980

*Prices vary depending on exact spec

How does it ride?

As I’ve spent the last year riding SRAM’s cable-operated GX Eagle on a hardtail, I thought it appropriate to fit this GX Transmission to a similar bike. With the rough and chaotic ride a hardtail often dishes out, especially on dry and fast trails, it would be a good test of chain retention and reliability of the system, as well as shifter ergonomics.

Installation is relatively straightforward and painless. SRAM’s walk-through videos are definitely worth watching as there are no shortcuts to getting the system set up, and once you’ve got a full understanding of how the components integrate it all makes sense.

With years of riding cable-operated gears and limited experience of electronic drivetrains on a mountain bike, I thought there would be a need to recalibrate my shifting behaviour. A mechanical system takes a concentrated effort to push a lever and shift the gears, and I’ll often find my thumb resting on (or hovering over) the smaller of the two triggers without any accidental gear shifts. With this AXS shifter, careful consideration is needed to the ergonomics to avoid any accidental shifts, especially when the trails turn rough. I ended up with the shifter sitting a touch more inboard on the bars than normal to prevent tapping it by mistake, and I’m sure there’ll be more fine-tuning to the position over time.

While I expected to have to tweak the shifter set up and my default hand position, I didn’t foresee the need to rethink how I change gear. Straight out into rooty, undulating singletrack, littered with braking bumps, I was immediately impressed by the precise and fluid shifting between gears. The cassette mapping tech controls the shift speed, so the gears change methodically, one-by-one, rather than skipping and stuttering over multiple cogs. You can’t just jump a load of gears with one push of a button, so sweeping from one side of the block to the other does take longer, but it’s also smoother and more precise. Combine this with the incredibly reliable and quiet shifting under load and I soon realised that this system shifted between cogs with such authority that last minute panic shifts are totally unnecessary. Tap the button and it changes gear, regardless of the terrain and how hard I was stamping on the pedals. It feels like a slightly slower, more methodical gear shift, but as it instills so much confidence, it freed up some headspace and allowed me to focus more on the trail.

So SRAM’s GX level Eagle Transmission may well be a mid-range take on its latest drivetrain technology, but it’s still a very big investment. At just under £1,200 for the complete drivetrain (r-mech, shifter, cranks, cassette, chain, battery and charger) it’s about 15% more expensive than the previous GX AXS parts, but it should be more durable and repairable if anything does go wrong. We’re already seeing 10-15% discounts on the X0 AXS T-Type parts, so it’s unlikely the full price will hold for long, either.

Looking at the weights listed for the pricier X0 and XX Transmission, it’s not overly hefty in comparison. Add in the revised battery placement and E-bike suitability and it feels like the pick of the range, with no real compromises. Considering the added durability, ease of set up, rebuildable rear derailleur and authoritative wireless shifting, and the marginal weight penalty over cable-operated GX Eagle seems justifiable, even if it’s still a considerable step up financially. Only more trail miles and a full dose of a British winter will highlight any shortcomings, truly test its durability and reveal its real-world running costs.