SRAM Eagle AXS: Wireless shifting and a matching dropper seatpost

by Dave Rome


SRAM has set the Eagle (cable) free. Almost an entire year after it was first sighted in pro racing, SRAM is finally ready to tell (and sell!) all of its new wireless 12-speed, single-ring mountain bike drivetrain. The new Eagle AXS drivetrains have been announced alongside the previously sighted SRAM Red 12-speed road groupset, and there’s a matching cable-free RockShox dropper post, too.

The new wireless components share the same AXS (“access”) moniker, and it’s a play on “access everything”. In short, AXS is a closed wireless frequency that allows an impressive level of cross-compatibility between mountain bike and drop bar components. Want to run an Eagle AXS rear derailleur and 10-50T cassette with the new Red eTap AXS drop bar shifters for that ultimate single ring gravel bike setup? You sure can.

This article takes a look at what’s new (and what’s not) on the mountain bike side. For an in-depth look at the wholly new SRAM Red AXS groupsets, including first ride impressions, see James Huang’s article here.


Building on mechanical Eagle

The new XX1 Eagle AXS and X01 Eagle AXS drivetrains are best defined as upgrade kits (except you currently have to buy the whole drivetrain) for existing Eagle mechanical groupsets. SRAM first released its XX1 Eagle and X01 Eagle 1×12 groupsets in March 2016, and has since trickled the technology down to impressively low price points.

The new Eagle AXS wireless builds on success of SRAM’s existing 12-speed mechanical drivetrains.

Eagle combines SRAM’s narrow-wide single chainring technology with a monstrous 10-50T 12-speed cassette to provide a 500% gear range. Such a large cassette allows the use of a larger chainring, and so riders are able to benefit from an increased gear range at both extremes.

The Eagle 10-50T cassette uses SRAM’s XD driver body, which can be retrofitted to just about any modern brand of hub or wheel on the market, except Shimano. And with a spacer, the Eagle cassette can even be fitted to the new wider, road-specific XDR driver.

The Eagle crankset is a carryover item to the new AXS drivetrain, too, and uses SRAM’s recently introduced DUB 28.99mm-diameter axle design. Where SRAM previously offered its cranks with GXP (24/22mm) and 30mm axles, the new DUB system greatly simplifies things, and there are bottom brackets to adapt the cranks to just about every mountain bike frame.

So with the crank, chain, and cassette effectively the same as before, what’s new with Eagle AXS? Well, it’s really just the rear derailleur and a right-hand shifter. And whether mechanical or wireless, there’s not a whole lot to differentiate Eagle XX1 and X01, either.

SRAM Eagle XX1 AXS wireless drivetrain
XX1 Eagle AXS in colours to match Nino Schurter and Kate Courtney’s jerseys.

XX1 Eagle AXS is made with cross-country racing in mind. The rear derailleur features a carbon cage and titanium hardware for reduced weight, and the new cassette offers an easily identifiable titanium nitride PVD coating in a rainbow finish. The same treatment is given to the chainring and chain.

SRAM Eagle X01 AXS wireless drivetrain
The X01 version is built a little more rugged and is priced marginally lower.

Built a little heavier and more rugged for trail and enduro use, the marginally less expensive X01 Eagle AXS components feature stainless steel hardware and an aluminium rear derailleur cage. The cassette is given a black and grey treatment, as is the chainring, while the chain gets the same rainbow colour as XX1 Eagle AXS.

Existing Eagle mechanical chains, cranksets, and cassettes are fully compatible with Eagle AXS. This means the use of rainbow-coloured components is optional – that is, if and when SRAM begins selling components separately. In a somewhat surprising (and rather heavy handed, if we do say so ourselves), SRAM will only sell the new Eagle AXS groupsets complete, at least for now.

SRAM Eagle AXS specifics

Much like SRAM’s mechanical trigger shifter, the compact Eagle AXS shifter offers a dual-button layout for shifting in both directions of the cassette with your right thumb. Additionally, the new AXS shifter offers a “Secret Sprint Paddle”, allowing shifts to a harder gear with the forefinger. In practice, it’s extremely similar to what Shimano has long offered with its existing mechanical paddle shifters.

SRAM Eagle AXS wireless shifter - sprint paddle
The ability to shift down the cassette with either your forefinger or thumb is a feature Shimano users will be accustomed to.

The new shifter will mount to the bar much like SRAM’s mechanical shifters, with either a separate clamp or the MatchMaker system, which cleanly integrates with SRAM brake levers. It’s powered by a single CR2032 battery, which is said to last about two years of use. And if you’re wondering, SRAM has made no announcement regarding a Grip Shift option.

Compared to the pulley cages on current Eagle mechanical rear derailleurs, the new AXS ones are 10mm shorter for better ground clearance (and likely a reduced momentum load on the clutch mechanism). Additionally, they’re said to sit slightly further forward for greater chain wrap on the cassette, which should lead to crisper shifts and improved cassette wear.

SRAM Eagle X01 AXS wireless drivetrain
Eagle is specifically designed for use with its 10-50T cassette. No tighter gearing options exist.

Just like mechanical Eagle, the AXS rear derailleurs are optimised for use with only the 10-50 Eagle cassette (or 11-50T if you’re using a regular Shimano-style freehub body). Where the Red eTap AXS rear derailleurs feature a new fluid damper system, the Eagle AXS derailleurs stick with SRAM’s impressively efficient and proven Roller Clutch 3.0 clutch mechanism for improved chain retention.

The rear derailleurs also offer a new Overload Clutch in case of direct impact. In the event of a hit, the internal motor will momentarily disengage for protection, before it then automatically reconnects and shifts the derailleur back to the last set gear. The feature was designed to protect the derailleur’s internal motor, but as a side benefit, it’s likely to prevent damage to the derailleur and derailleur hanger, too.

The Eagle AXS derailleur battery is the same as that used on the new Red eTap AXS 12-speed road groupset and RockShox Reverb AXS dropper seatpost (which is also the same as what SRAM used for the first-generation eTap groupset). It’s 25g and is claimed to last for 20 hours of riding time between charges. That number may seem low, but it’s a claimed figure likely based on the higher frequency of shifting when riding off-road and is also impacted by the greater motor load from to the stiff clutch mechanism. A full charge, done with the provided charger, takes an hour.

As was the case with SRAM Red eTap, the system has an automated power-off and battery conservation mode when the bike is stationary for a period of time, and a press of any shift button wakes the system. Both the derailleur and shifter are rated to the highest standard of dust and waterproof ingress protection (IP69K), and so should withstand submersion, pressure washing (not recommended), and similar abuse.

While we’re still waiting to get our hands on the new drivetrain, one major question is whether the wireless system shifts fast enough for the demands of technical mountain biking. SRAM states the factory-set speed has been increased from its original Red eTap groupset, and while James’ experience with the new Red eTap AXS proves this to be true, it’s still not as lightning quick as other electronic or even mechanical drivetrains.

SRAM Eagle AXS wireless
While the derailleur itself is heavier than the mechanical counterparts, a lack of wires and a lighter shifter produce an almost equal end result. (Shifter not pictured to scale with derailleur).

All told, SRAM claims XX1 Eagle AXS saves approximately 5g over its mechanical counterpart, while X01 Eagle AXS saves 15g. Of course, this is dependent on what type, and how much, cable and housing is used on the original system.

Eagle AXS XX1 and X01 are ready for sale now, with complete drivetrains priced at US$2,000 / £1950 / €2100 / AU$3,300 and US$1,900 / £2000 / €1900 / AU$3,200, respectively.

There’s an app

All SRAM AXS components are fitted with Bluetooth for easy connection and control via SRAM’s AXS smartphone app. While the app allows you to set service internals and offers a few other features, its main purpose is for easy customisation of AXS components.

SRAM AXS phone app
All firmware updates and settings will be done wirelessly through the SRAM AXS app, which will work with both iOS and Android smartphones.

It’s in this app that you’d set up your preferred shifting styles and allow for cross-compatibility. For example, the right-hand shifter and its front-facing Sprint Paddle can be set to control the new Reverb AXS dropper. Likewise, you can also set up the Eagle system with road Blip shifters.

Just on cross-compatibility, it’s worth noting that SRAM’s new Red eTap AXS features a specific chain that isn’t cross-compatible with Eagle. So while you can use Red eTap AXS shifters and 1x cranks with an otherwise Eagle setup, the chain and cassettes are not cross-compatible.

Similarly, AXS components will only work with AXS components. Unfortunately for those with 11-speed Red eTap, you will not be able to “AXS” this newfound connectivity or cross-compatibility.

Why wireless?

It’s certainly a fair question. After all, mechanical cables have been a reliable choice in mountain biking since the days of Joe Breeze, Charlie Kelly, Gary Fisher, Tom Ritchey, and others riding the hills of Marin County.

Electronics aside, fewer parts typically means there are fewer things to go wrong. And the AXS system is extremely bare-bones. There’s no worry about how to route that cable housing along the frame and past the moving suspension frame pivots. There are no cables for trail elements to contaminate. There’s no cable or wire for an evil shrubbery to snatch. And no concern for where to store a battery inside the frame.

Cables aside, electronic drivetrains are just impressively set-and-forget (just remember to keep them charged). No matter the conditions, there’s no cable or clutch friction for you to overcome at the shift lever – the motor handles that. And the newfound cross-compatibility between road and mountain offerings is a major bonus that’s made possible with electronics.

Installation is extremely simple, too. And as many mechanics will attest that SRAM’s original eTap groupset was the easiest thing to install, Eagle AXS is even easier again. Bolt on the shifter, bolt on the derailleur, adjust two limit screws and use the supplied chain gap tool to set the pulley wheel gap to the cassette, and you’re just about done.

All of this is great (in my opinion), but there’s one component installation where wireless is truly exciting: dropper seatposts. RockShox, SRAM’s suspension brand, has joined the AXS party with its first wireless dropper seatpost, and the installation is likely to be as basic as fitting a rigid post.

RockShox Reverb AXS dropper

RockShox Reverb AXS wireless dropper
For anyone who’s ever spent time fishing cable housing through a frame and up a seat tube will attest, a wireless dropper post makes a whole lot of sense.

Both Magura and KS already offer wireless dropper seatposts, and so it was only a matter of time before SRAM would join them. And we all knew the RockShox Reverb AXS was coming; after all, the likes of Jolanda Neff and Nino Schurter have been spotted riding them for months.

The new Reverb AXS uses the same battery as the derailleur, for a claimed 40-60 hours of riding between charges. The wireless handlebar dropper remote works like a regular dropper post, and holding the button keeps the post’s valve open for you to set the saddle height wherever you desire. And just like a regular dropper, with the button pressed, you unweight the saddle for the post to go up or sit to lower it.

The Reverb AXS features internals similar to the existing fully-hydraulic Reverb post, albeit with a few upgrades that should result in smoother and more consistent operation. The internal floating piston (IFP) is now lower-friction for less effort in changing the post’s height, while refined grease and oil should help things along, too.

What’s most interesting, though, is the new Vent Valve, a feature that should allow quick fixing of any unwanted sag in the post. Such sag occurs when the oil and air get on the wrong sides of the IFP, and the Vent Valve will allow users to purge the system of air without having to disassemble and rebuild the post. It’s a feature that’s proven extremely popular with the German-designed BikeYoke Revive post, which allows such revival (hence the name) with a valve at the top of the post. From what I can tell, the Reverb AXS’ valve is located at the bottom of the post and so you will need to remove the post from the bike should you need this feature.

The post also features an IPX7 waterproof rating, meaning it’s tested to survive in one meter of water for 30 minutes, but hasn’t been tested for dust proofing. Eagle AXS offers a higher protection rating than the Reverb.

RockShox Reverb AXS wireless dropper
The new Reverb AXS will be sold with the remote, battery, and charger included. Pictured remote not to scale of the post.

Due in stores now, the Reverb AXS is available in diameters of 30.9, 31.6, and 34.9mm, with travel lengths of 100, 125, 150 and 175mm. There’s currently no 27.2mm-diameter option, which will, unfortunately, limit its acceptance with many gravel and cross-country users. Weights are TBC.

Expect the post, including remote, battery and charger to retail for US$800 / £700 / €800 / AU$1,300.

SRAM is certainly committed to its new AXS wireless protocol, and it’s safe to assume we’ll see more compatible components appear in the future. Whether that’ll be suspension products from RockShox, data acquisition products from Quarq or just more drivetrains, it’s certainly an interesting space.

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