SQUIRREL_13115393
SRAM’s GX Eagle AXS Transmission drivetrain has perfect shifting performance regardless of weather or trail conditions, but its electrical components failed during 2,100km of testing.
Over the 16-month test period, I racked up over 2,100km, 82,700 metres of ascent and descent, and 171 hours of riding with a single GX Transmission drivetrain.
Despite GX being the brand’s most affordable (£1,180 / $1,099/ €1,300) aftermarket entry into its direct-mount, derailleur-hanger-free T-Type ecosystem, it shifts identically to the more expensive X0 and XX variants, changing gear in the same precise way time and time again.
Readily available replacement parts boost repairability and refreshing the derailleur to prolong its lifespan isn’t a headache.
Compared to SRAM’s Eagle drivetrain components and Shimano’s 12-speed systems, it’s leagues ahead in terms of functionality, reliability, and longevity, helping justify the price further.
The test period hasn’t been faultless, however; clutch tension could be higher and the derailleur needed repairing under SRAM’s warranty. But, in my opinion, these feel like small bumps in the road rather than insurmountable issues; read on to find out why.
SRAM GX Eagle AXS Transmission drivetrain headline figures
- Total weight (including 165mm cranks with 32t chainring and bash guards, rear derailleur with battery, 126 link chain with Power Lock, 10-52t cassette and Pod Controller Ultimate): 2,003g
- Total price (including 165mm cranks with 32t chainring, rear derailleur, 126-link chain, 10-52t cassette and shifter): £1,180 / $1,099/ €1,300
Where does GX Eagle AXS Transmission sit in SRAM’s drivetrain line-up?
GX is SRAM’s third-tier level of components, usually sharing much of the same technology as its more expensive counterparts. Thanks to differences in construction materials and processes, it costs less.
GX Transmission, therefore, is positioned below the range-topping XX and second-tier X0 Transmission drivetrains.
It sits above S-1000 – which is the Transmission equivalent to NX-level components – but this is only available as original equipment (OE) on full bikes rather than as a full aftermarket groupset.
Compared to the rest of SRAM’s family lineage, Transmission components run parallel to Eagle drivetrain components (SX Eagle through to XX1 Eagle), and bar some exceptions (such as the Pod Controllers), neither range is compatible with the other.
SRAM GX Eagle AXS Transmission drivetrain details and specifications
I’m going to run briefly through GX Transmission’s specs below, but if you’d like more depth on all its technological innovations, please read our GX Eagle Transmission news story.
SRAM GX Eagle AXS Transmission 12-speed rear derailleur specifications
Different in design to X0 and XX, the GX derailleur’s battery is mounted horizontally rather than vertically. It sits between the vertical Full Mount struts.
Also changed for GX is the motor’s gearbox. Both these differences are claimed to better protect the derailleur from impacts.
Like the other derailleurs in the Transmission range, some of its parts are replaceable.
Tools aren’t required to remove the cage and clutch; it rotates off the derailleur’s P-knuckle.
Its skid plate and outer parallelogram link are also replaceable, removed by using an Allen key.
The cage’s inner plate is made from steel (rather than aluminium on X0 and XX), increasing weight but also potentially robustness.
Like X0, however, it forgoes XX’s Magic Wheel jockey wheel – that can continue to rotate even if its spokes are blocked – reducing cost.
Just like all other Transmission derailleurs, GX uses SRAM’s Hangerless Interface and Full Mount frame-attachment design, securing it directly to the bike’s frame at the wheel axle.
My GX Eagle AXS Transmission derailleur weighs 491g and costs €480.
SRAM AXS Pod Ultimate Controller specifications
While a more affordable AXS Pod Controller is available to buy – it costs €180 instead of the Ultimate version’s €240 – my test GX Transmission group was shipped with the top-spec Ultimate.
The main difference between the two, except for a silver metal-effect flash, is the Ultimate's replaceable buttons.
Concave and convex buttons are supplied with the Ultimate controller, while the standard one gets fixed flat versions.
Both have a flippable design, however. The same controller can be used on either the left- or right-hand side of the handlebar.
There are two mounting options – the Bridge Clamp, which mounts it directly to your brake lever or an Infinity Clamp bar mount.
My Pod Controller Ultimate with Bridge Clamp weighs 55g.
SRAM GX Eagle AXS Transmission cassette and chain specifications
Like the other Transmission cassettes, GX’s ratios have been tweaked over SRAM’s drivetrain counterparts.
This increases tooth count on the second and third biggest sprockets to 44t and 38t respectively. The 52t lowest gear remains, as does the 10t highest ratio.
Like the rest of SRAM’s cassettes, it uses the XD Driver freehub, rather than the HG or Micro Spline standards, to accommodate the 10t cog.
Again, sharing technology with its more expensive counterparts, its X-Sync design and carefully placed shift ramps should mean gear-change performance has been prioritised above all.
Its Mini Cluster – where the four smallest gears are machined from a block of billet steel – is pinned to the remaining eight gears, which are, in turn, pinned to one another.
While it’s less high-tech than the X-Dome XX cassette’s construction, it's intended to balance cost (€300) and weight (448g).
The GX chain features the same flat-top design as the other Transmission groups, but this one gets solid pins and is finished with a silver nickel outer coating and a chrome-hardened inner.
At its full 126-link length, it weighs 285g and costs €60.
SRAM GX Eagle AXS Transmission crankset and chainring specifications
The forged aluminium cranks are matched with an aluminium chainring and bolt-on composite bash guard.
All Transmission cranks are built for a 55mm chainline, use a Transmission-specific direct-mount chainring and run on SRAM’s DUB bottom bracket standard.
A 165mm crankset, 32t chainring and bash guard costs €240 and weighs 724g.
SRAM GX Eagle AXS Transmission installation and setup
While the initial setup and install feels like a lifetime ago back in mid-June 2023, I’ve swapped GX Transmission between multiple bikes during the test period. Each time I removed and installed it, I remembered how easy the process is.
Once familiar with the simple installation instructions, getting any Transmission drivetrain (including GX) ready to ride is one of the most repeatable processes in the MTB world.
Without b-tension or limit screws, as long as you follow the correct install and set-up process for your bike, it's virtually impossible to go wrong. It's significantly easier than traditional drivetrains to get ready to ride.
Here, Transmission is unparalleled. For many, how easy it is to bolt to your bike will justify the cost.
SRAM GX Eagle AXS Transmission performance
I tested GX Eagle AXS Transmission over a period of 16 months, racking up over 82,700 metres of ascent and descent, 171 hours of riding, and over 2,100km.
While I’ve certainly not been protective of the drivetrain, I’ve maintained it how I’d expect a consumer who spent over £1k on a product would.
That means it’s been lubed and looked after well. Post-ride clean ups to remove grit and dirt were performed religiously, as was re-lubrication with Silca’s Super Secret Chain Lube and more recently White Lightening’s Clean Ride drip wax lubes.
Testing has taken place on multiple bikes including my long-term Marin Rift Zone XR, my partner’s Specialized Stumpjumper, and most recently, a Marin Alpine Trail.
Testing has happened on my rough and ready home enduro trails in Scotland’s Tweed Valley through to bike park laps in European resorts.
Needless to say, it has had a thorough workout.
SRAM GX Eagle AXS Transmission rear derailleur performance
GX Eagle AXS Transmission derailleur robustness
The GX Transmission derailleur is remarkably robust.
During the test period it has been smashed and slammed into rocks and roots, the inside, sharp edges of ruts, bashed against the floor in crashes and been subject to continuous soakings, and barrages of dust and mud all without flinching.
Remaining as straight today as it did when it was first fitted, the GX derailleur’s main body and cage are both up to the punishment even the hardest riders can dish out.
The weightier but tougher steel cage construction improves GX's lifespan, resisting bending better than the aluminium version.
The parallelogram’s pivot points have remained slop- and play-free during the test period; this is impressive given it’s one of the weakest points on most derailleurs.
Likewise, the P-knuckle to cage join is still stiff and robust, exhibiting only minimal play.
Both jockey wheels – while showing a bit of wobble when rotated without a chain – spin freely and smoothly with the drivetrain engaged. Their teeth are sharp and haven’t reduced in height.
Electrical gremlins
But it hasn’t been plain sailing.
After 146 hours or 1,786km of riding the electronic components within the derailleur stopped working.
Pressing the shifter button elicited no response from the derailleur despite trying it with multiple, fully charged batteries. Likewise, pressing the derailleur’s own AXS button couldn’t wake it from its slumber.
SRAM UK’s service centre was quick to help by initially suggesting a hard reset. Unfortunately this didn’t revive it, and it had to be returned to SRAM for further investigation.
SRAM informed me the derailleur was repairable, but stock issues meant the parts required weren’t available. SRAM replaced it free of charge under its warranty.
A consumer experiencing this type of failure would also have the issue covered under SRAM’s two-year warranty, and likely beyond as a goodwill gesture.
While SRAM was coy about the specifics that caused the derailleur to fail, I’ll happily speculate the battery’s horizontal mounting position and water ingress is likely the cause.
Water can sit on the derailleur’s flat battery ‘dock’, getting trapped between the battery and the derailleur.
The sprung battery connector pins also sit on the dock’s flat surface, pointing vertically, and are likely the moisture-ingress point.
Their spring mechanism corrodes, which stops the pins from returning to their full height to engage the battery's connecter. Unable to connect, the derailleur is without power.
This is just speculation, however, and isn't something I can prove definitively.
Fastidious post-ride and post-wash drying and cleaning of the battery dock would prolong its lifespan.
However, the vertically mounted battery found on the X0 and XX derailleurs means they may be more electronically robust than GX. The XX Transmission I initially reviewed has now clocked over 172 hours or 1,938km of faultless riding.
Rebuilding the SRAM GX Eagle AXS Transmission derailleur
Despite the electrical failure, during the test period I didn’t need to take apart or replace any of the GX derailleur’s mechanical parts.
While its parallelogram and cage are bruised and battered, the damage is only aesthetic rather than functional.
But rebuilding it is simple; the cage and clutch simply unscrew, and if you want to separate the cage from the clutch, only a few readily available tools are needed.
Likewise, removing and replacing the skid plates and outer parallelogram’s link is just a case of unscrewing them.
SRAM GX Eagle AXS Transmission derailleur shifting performance
GX Transmission's shifts are class-leading and identical to the group’s more expensive X0 and XX counterparts.
There’s no delay between button press and derailleur action; changes are quick and crisp.
As long as everything is set up according to SRAM’s instructions, there are never any missed shifts or spluttery cog-grinding hiccups.
This is true for all weather and trail conditions; whether it’s covered in gloopy mud, fine sand or grit, or icing-sugar dust, shift quality is identical.
Unlike mechanical drivetrains that require a specific amount of thumb movement to push the lever to engage the next gear, or SRAM AXS Eagle drivetrains that require careful setup, Transmission has the most reliable and consistent shift feel of all derailleur drivetrains currently on the market.
Of course, if the derailleur has rotated backwards on its full mount, it needs trimming (the equivalent to adjusting cable tension), or there’s a physical blockage in the drivetrain, shift quality nosedives – but this is true for any drivetrain.
The biggest gripe I’ve heard about Transmission derailleurs is about the shift speed. Many state it’s slow to respond and change gear compared to the original AXS derailleurs, especially if you’re changing multiple gears at once.
If you shift dump (where almost all the gears are changed at once) either up or down the cassette, you’ll have to wait longer than you would with a mechanical derailleur or AXS drivetrain derailleur, but there’s only a marginal difference.
And the trade-off is impeccable shift performance, which is totally worth it.
On-power shifts are also exceptional. Changing gear during a high-powered pedal stroke elicits a satisfyingly crisp click as the chain moves from one cog to the next.
If anything, re-learning shift behaviour is the hardest thing. With Transmission, you don’t have to soft pedal as you change gear; instead, cranking hard gets the best feeling changes.
Transmission’s high-quality on-power shifts come alive when the group is combined with the power of an ebike motor. Mindless shifting – whether you’re hard on the gas or not – isn’t punished; if anything, it’s rewarded with satisfyingly smooth changes between ratios.
You can change exactly when you want to, rather than adapting to the drivetrain’s conditions for spot-on shifting. It’s incredibly impressive.
SRAM GX Eagle AXS Transmission derailleur-clutch performance
While clutch tension on Transmission derailleurs has been increased over the previous-generation AXS drivetrain derailleurs, it could be increased further.
Chain derailments off the chainring are much less frequent, but they still happen – although only in the gnarliest terrain. GX Transmission’s clutch tension is identical to X0 and XX’s, so the amount of chain control is the same regardless of how much you spend.
Clutch tension will always be a balance between smooth gear shifting, free-moving suspension action and chain control – I still think SRAM’s clutch tension could increase.
This is particularly true for AXS derailleurs, where cable-pull force isn’t an issue; I say let the motor and battery deal with the increases in force required to shift cogs.
Riders who tackle the gnarliest terrain will benefit from a chain device or other chain-damping measures – such as STFU chain guides or a chainring chain damper (from the likes of Ochain or Rimpact) to eliminate chain derailments.
Looking at the wear on the teeth of this drivetrain’s chainring reveals just how much the chain still moves about, despite the impressive control of the GX derailleur.
SRAM AXS Pod Ultimate Controller performance
While the Pod Controller’s design might not be to everyone’s taste, I like the way it works.
It’s not trying to emulate cable-shifting trigger pushes like Shimano’s XT Di2 does. Instead, the Pod Controller is a reimagining of how shifters should look if cable shifting never existed.
Some say the feedback through the buttons isn’t stiff enough, resulting in mis-shifts. I’m not sure I agree, and can’t think of a single time I’ve accidentally pushed the shifter button when riding rough terrain – nor can I think of a time I’ve missed the button altogether.
They’ve proven to be robust and battery life is impressive. The original coin cell is still in the shifter 171 hours of use later.
While the Infinity Clamp offers more adjustment than the Bridge Clamp – which is good because the Bridge Clamp’s range is limited – adding an extra clamp to the handlebar goes against the stripped-back AXS aesthetics.
What works for you will be down to your own preferences – and Transmission is compatible with all current AXS controllers if the Pod isn’t to your tastes.
SRAM GX Eagle AXS Transmission cassette and chain performance
Alongside the derailleur, the cassette and chain are the workhorses of GX Transmission.
Increasing the second and third lowest gear ratios, and reducing the jump to the easiest, has made them way more usable.
I frequently use Transmission's gear number two (44t) while climbing, when previously I’d already have made the jump to the 52t cog from the 42t. Likewise, gear three’s 38t (instead of 36t) makes it way more usable in a broader range of climbing scenarios.
The Transmission cassette is a massive leap forwards over Eagle drivetrain versions, putting it on par with Shimano’s carefully considered ratios.
The chain hasn’t snapped, bent or needed any maintenance beyond lubrication.
SRAM GX Eagle AXS Transmission chain and cassette wear
The cassette’s cogs are showing only slight signs of marking or scratching from the chain moving up the shift ramps.
It has proven to be aesthetically more robust than Eagle drivetrain cassettes from any of SRAM’s lines (SX through to XX1), which lose their coloured coating in shift zones very quickly.
Using a chain-wear tool, after 2,100km the GX chain was showing minimal signs of use compared to a new one.
SRAM GX Eagle AXS Transmission crankset performance
My foot positioning on the pedals means I’m very tough on cranks, wearing off the anodised or painted surface, sometimes after only one ride.
The GX Transmission cranks' finish proved to be more robust than GX Eagle drivetrain and Shimano’s finishes, but it still wore off after a couple of weeks of riding.
After 171 hours of use, the wear has stabilised, but the cranks aren’t exactly pretty.
They are, however, robust. They’ve brushed off rock strikes and general mistreatment impressively, showing no signs of critical damage or bending
And because they don’t have a hollow construction – like Shimano’s Hollowtech II cranks – it’s impossible to wear through the crank’s outer skin. This has happened to me with a pair of Saint cranks.
Showing signs of use, the lower bash guard has dents, scratches, and nicks taken out of its surface, but it’s still perfectly straight and true.
It’s the same story for the chainring; it runs as straight today as it did when it was new.
Its teeth show very few signs of wear. They haven’t been significantly hooked or rounded by the chain and haven’t been damaged during use.
There is one exception, however.
Where the chain exits the lower part of the chainring towards the derailleur, three teeth have been significantly blunted and worn down. This is caused by the chain continually coming on and off the chainring as it slaps about over rough terrain.
While you’d think the teeth being reduced to stumps would impact chain-retention performance, derailments occur more frequently at the top rather than the bottom of the chainring.
After the number of kilometres the chainring has covered, I think its wear life is impressive. Replacements are relatively affordable at €47.
Unfortunately, SRAM’s eight-bolt mounting pattern means rotating the ring to even out wear isn’t possible.
How does SRAM GX Eagle AXS Transmission compare to SRAM GX Eagle AXS and Shimano SLX M7100?
SRAM’s GX Eagle AXS Transmission costs £1,180 / $1,099 / €1,300, while an equivalent GX Eagle AXS drivetrain (with alloy cranks) is £913 / $983 / €1,022.
Forgoing electronic shifting means Shimano’s SLX M7100 is significantly cheaper at £398.94 / $394.94 / AU$734. Shimano doesn’t offer aftermarket 12-speed Di2 shifting.
While Shimano’s closest equivalent looks like a veritable bargain compared to both of SRAM’s AXS groupsets, it still uses cable rather than electronic, wireless shifting.
In terms of weight, this is how the three compare:
- SRAM GX Eagle AXS Transmission: 2,003g
- SRAM GX Eagle AXS drivetrain: 1,850g
- Shimano SLX M7100: 1,864g
GX drivetrain is the lightest of the three, with SLX M7100 in close second. GX Transmission is around 150g heavier, with most of this increase coming from the derailleur.
For traditional drivetrain systems, you’ll need to add back in the weight of a derailleur hanger, which can vary depending on the manufacturer.
Comparing installation and setup
Once you’ve mastered the instal instructions, Transmission – whether that’s GX, X0 or XX – is by far the easiest and simplest groupset to install and fit. It’s impressive and a massive draw.
On-trail performance and reliability
Shimano’s adjustable clutch certainly beats SRAM’s non-adjustable versions hands down, but the rest of the M7100 derailleur – particularly its skinny cage, parallelogram and B-knuckle – let it down.
In my experience, the failure rate of Shimano derailleurs is much higher than SRAM ones, with the Transmission generation tipping that even further in favour of SRAM.
Transmission does away with the pivoting B-bolt design of SRAM’s Eagle AXS drivetrain derailleurs, improving chain control and shift performance while reducing noise.
Shimano’s on-power shifting is noteworthy, but if you push the shifter’s trigger when the derailleur isn’t lined up with a cassette shift ramp, the system will splutter or make noise. This isn’t an issue with Transmission.
Repairability
While some spare parts for derailleurs have always been available – particularly the cage and jockey wheels – SRAM’s Transmission ushers in a new period of repairability.
This certainly goes some way to justifying the especially lofty price tag commanded by even the mid-level GX Transmission, but it’s still far from perfect.
To improve things further, SRAM could make the inner parallelogram’s links replaceable, along with the B- and P-knuckles. Still, compared to the rest of the market, it’s leagues ahead.
SRAM GX Eagle AXS Transmission drivetrain bottom line
SRAM’s GX Eagle AXS Transmission drivetrain is a standout performer in all domains, whether that’s installation, maintenance or performance on the trail.
That’s fortunate given the asking price. But when lined up next to its closest competitors, also from SRAM’s range – X0 and XX – it looks a bargain, because performance between the three is indistinguishable.
Yes, it’s quite a bit heavier and not as sleek-looking, but once you’ve clocked up a few thousand kilometres on any drivetrain, it’s going to look well-used.
However, performance during the test period wasn’t perfect. The electronic portion of the derailleur failed, but was replaced under SRAM’s generous warranty, and I’d like more clutch tension for improved chain control.
Because the warranty covers the former and an inexpensive chain device helps to improve the latter, it’s hard to justify docking points from GX’s otherwise stellar performance.
If you’re looking for faultless shift performance, easy installation and maintenance, impressive chain control (compared to SRAM’s previous derailleurs) and an incredibly robust drivetrain that’s still within the realms of affordability, I couldn’t recommend GX Transmission enough.
SQUIRREL_13115393
Product
| Brand | sram |
| Price | 1300.00 EUR,1180.00 GBP,1099.00 USD |
Features
| Features | Weight SRAM GX Eagle AXS Transmission derailleur (with battery): 491g SRAM AXS Pod Controller Ultimate (with Bridge Clamp): 55g SRAM GX Eagle AXS Transmission cassette: 448g SRAM GX Eagle AXS Transmission 126 link chain with Power Lock: 285g SRAM GX Eagle AXS Transmission 32t chainring with bash guards: 159g SRAM GX Eagle AXS Transmission 165mm cranks: 565g Total: 2,003g |
