Thankfully, the next step in drivetrain progression doesn't look like it involves adding yet another cog into the mix. SRAM's new Eagle AXS 12-speed drivetrain ditches the cable and housing for an encrypted wireless network, a tiny electric motor, some circuit boards, and a few batteries.
The battery-powered Eagle AXS system will be available in two different flavors: the XC-focused XX1 group sports titanium hardware and a carbon fiber derailleur cage at $2,000 USD, while the X01 setup is said to be more enduro-friendly and skips the fancy materials to save $100.
Both versions of Eagle AXS employ the same cranks, cassette, and chain as the mechanical version, with the only difference being the 'oil slick' finish (officially called "Rainbow") on the latter two (XX1 only) that is sure to divide opinions. If you're fine with the color, you'll be able to pick up either group this coming April, although SRAM won't be selling the components separately for at least another month - you'll have to wait a while if you just want the shifter and derailleur.
Surprisingly, an entire Eagle AXS XX1 group is claimed to come in 5-grams lighter than its mechanical sibling, putting it at 1,451-grams without a bottom bracket. X01 is 15-grams lighter overall, so it sits at 1,487 without a bottom bracket. SRAM declined to provide me with individual component weights, but the numbers above do include the 25-gram battery, too.
Eagle AXS Details
• Intended use: cross-country, trail, enduro
• Wireless encrypted network
• 20+ hour battery life
• AXS app configures buttons
• Weight: 1,451g (XX1, claimed); 1,487g (X01, claimed)
• MSRP: $2,000 USD (XX1), $1,900 USD (X01)
• Availability: April, 2019
• More info: www.sram.com/sram
Historically, the progression of mountain bike drivetrains has mirrored the ever increasing number of cogs out back and, more recently, the disappearing chainrings up front. As the number of cogs increased, so did the performance, with today's top drivetrains offering 11 and even 12 cogs, along with lower weights and shift speeds that should impress even the saltiest curmudgeon who's still saving that 8-speed XT drivetrain for ''just the right bike.''
What will a 13th cog do at this point? Not much and XTR Di2 proved, at least to me, that we've got to the point where it's going to take electronics to improve shifting speed and precision. Apparently, SRAM thinks the same, although they are at pains to stress how Eagle AXS is in no way a replacement for existing mechanical drivetrains, but rather just an option. Fear not, cables and housing aren't going anywhere for a long, long time, and owning an AXS drivetrain doesn't lock you into any proprietary parts, save for the shifter and derailleur. The same XD driver and standard Eagle chain, cassette, and cranks will play nice with the AXS parts.
The Eagle AXS Derailleur
Look ma, no cable. After plenty of teasing, SRAM's wireless mountain bike drivetrain will finally be available this coming April for $2,000 and $1,900 USD.
The real crown jewel of the AXS system has to be the new derailleur that hides a small electric motor, an even smaller gearbox, and TWO different clutches inside of a design that looks like it belongs on Batman's trail bike. There's a lot going on inside this thing, and it's been in one stage of development or another for the past six years after first starting life as an 11-speed prototype.
It was still very early days back then, and it was decided to focus on the mechanical 12-speed Eagle group rather than a wireless system. At least for a while.
Just a small selection of prototype AXS derailleurs. With six years of development behind it, you can bet there are plenty more behind closed doors.
Those six years saw the AXS prototypes go from roughly constructed proof of concepts to specially designed units that included small windows so the engineers could literally look inside to see how the gearbox was holding up. Wait, a gearbox? The electric motor spins at around 80,000 RPM, which is far too fast to be of any good when it comes to shifting... Unless there was a tiny transmission that turned it into the torque required to move the derailleur left and right.
That's exactly what SRAM did by designing and manufacturing their own gear wheels that, according to them, will last the life of the derailleur.
See that little window? That was installed so engineers could see how the gear wheels were holding up during testing.
If the battery that clips onto the back of the derailleur looks familiar, that's because it's the same as you'll find on the wireless Reverb AXS and their existing wireless road groups. And speaking of wireless road groups, you wouldn't be silly for thinking that Eagle AXS borrows tech from SRAM's RED eTap setup, but you'd also be wrong for the most part.
Aside from the battery, the derailleur has no relation to the RED eTap unit whatsoever. It uses a more powerful motor, a completely different gearbox that's more robust, and the derailleur itself gets much wider pivots for more rigidity. SRAM also increased both the chain wrap and the ground clearance (by 10mm) compared to the mechanical Eagle derailleur.
You're probably wondering about why this thing has two clutches. There's the now-normal one-way clutch that helps keep the chain on, but there's also the "Overload clutch." That important-sounding device isolates that aforementioned tiny gearbox from the forces of you smashing the derailleur into a rock. Internally, it's basically a one-way bearing, a friction device, and a little cylinder that slides in and out that releases the gearbox from the derailleur.
With all that stuff in there, it's a wonder how the complete group comes it at basically the same weight as the mechanical system, even with the missing cable and housing.
Weight? Price? SRAM wasn't keen on sharing individual specifics of each component yet, but it's probably fair to assume that the first one is low and the second one is high.
The Eagle AXS Shifter
Wait, who forgot to string the cable and housing?!
With no need to pull or release a silly shift cable, SRAM could come up with any arrangement of buttons that they wanted, and they did exactly that over the previous six years of development. Early prototypes included simple push-buttons that, while working just fine, were also really more to test the system as a whole then resemble anything a consumer would be offered.
SRAM pulled out a half-dozen of these at the demo, and some of them looked pretty clever to me, but the version that they went with wasn't what I expected to see.
Just four examples of what SRAM came up with for testing shifter design.
Rather than a nearly invisible collar and button arrangement, the AXS shifter looks kinda like, well, a shifter that doesn't have a cable sticking out of it. It's a bit smaller than a normal SRAM clicker, and it attaches to the handlebar via the usual MatchMaker clamp, but that's where the similarities end.
Instead of a thumb paddle and release trigger, there are actually three 'buttons' to choose from: the two under the bar would usually be setup to move the derailleur in opposite directions, and the third button that sits on the front of the shifter is designed to go to a harder gear if you bump it with your knuckle. SRAM is calling it the "secret sprint paddle" because it seems to work really well in those settings, but you can make any of the three "touch points" (that's what SRAM's calling the buttons) control shifting in any direction or even take command of your Reverb AXS dropper post, all via the AXS app. More on that later, though.
How it All Works
The ''secret sprint paddle'' is a button that you can easily hit with your knuckle while out of the saddle. I found it difficult to hit by accident, too.
If you made it this far, you'll probably want to know how this whole Eagle AXS thing works. So, what exactly happens when you shift?
First, the AXS components will all auto-sleep and auto-wake, just like the Reverb post, and you grabbing your bike is enough to tell the computer to get ready for action. When the time comes to shift, a signal is shot out to the derailleur over an encrypted wireless network, at which point the little motor fires up from 0 to fast as hell near instantly. That's put through the gearbox that converts it to torque and moves the derailleur left or right. Sounds simple, right? It happens in the blink of an eye, and you'll hear a tell-tale 'vvvvt
' as the derailleur moves the chain.
Will encrypted wireless networks spell the end for shift cables? Highly unlikely, at least not in the foreseeable future.
There's no cable, so that means that tension adjustments are a thing of the past, but you'll still need to setup your limit and B-tension screws. And what if you bend your hanger or the derailleur itself? First, you'll need to calm down after nearly destroying your very pricey derailleur, and then the solution, at least to sort the shifting out temporarily, is to use the button on the underside of the shifter. You can trim the derailleur a tiny amount in or out using this button.The AXS App
No, you don't need to use the AXS app to use computerized Eagle on your bike, but you'd be missing out on one of the group's neatest features: the ability to customize which button does what. The app is free and available for both iOS and Android devices, and it looks like it was designed for a simpleton like myself because it's very easy to use. Want your Reverb AXS remote on the left to shift to a higher gear, the shifter button in the right to move the chain to an easier gear, and the ''secret sprint paddle'' to control the Reverb? Not a problem and as easy as tapping your phone's screen a few times.
You need to press that small button on the back of the remote to pair your Eagle AXS, something that also keeps ''friends'' from messing with your bike. The AXS app lets you choose which button controls what, from the shifter to the Reverb remote.
I did exactly that on the side of a desert singletrack in Tucson, Arizona, and managed to figure it out in around 30-seconds, which means that most people will do the same in about half the time.
The AXS Batteries
Just like the Reverb AXS dropper post, the Eagle AXS drivetrain employs two different batteries. Up in the shifter is a common CR2032 that you can get from anywhere, and SRAM says to expect around two years of life until it needs replacing.
Down at the derailleur, you'll find the same clip-on battery that powers the wireless Reverb post, as well as SRAM's RED road drivetrain, and you can even swap between the three if you needed to. Because the motor requires a decent amount of juice, you can expect around 20-hours of battery life from this little guy, which is half the time that it's supposed to last on the Reverb. Still, that's probably many thousands of shifts, and there's a battery display light that'll tell you when it's time to plug things into the wall.
The Eagle AXS battery is the very same as what powers the Reverb AXS post and the RED eTap drivetrain.
Of course, 20-hours and thousands of shifts is a far cry from forever, so if you're the kind of person who doesn't remember the last time you checked your tire pressure or lubed your chain before a ride, you might not be the ideal AXS customer.
What happens if your SRAM battery goes flat on you during a ride? You're stuck in that gear, I'm afraid, or you can swap in the Reverb's battery if you prioritize shifting over seat height. Or, at just 25-grams each, you could slip a spare battery into your bag or pocket as a backup. While SRAM won't share the exact price of an Eagle AXS battery quite yet, a RED eTap battery can be had for around $50 USD, so expect a spare AXS unit to be around the same price.
On The Trail
Without a cable in sight, this Yeti SB130 was probably an extremely easy build.
So, how does all this fancy stuff perform? I spent a few days using the AXS group down in Tucson, Arizona - not enough to call it a review - but my first impressions are that I need to take back some of my shit talk. I went into the rides probably thinking the same thing you guys are: "Why do I need this? Cables work fine, and I can fix that stuff in minutes. And even an entry-level drivetrain shifts really damn well these days.''
Well, no one needs
it, but then I hit the buttons a few times and, well, it's pretty frick'n neat if I'm honest. The thing is that it should always nail the shift, no matter what. If it can offer that type of consistency, day in and day out, then it has a reason to exist. It did exactly that during my all too brief time on it.
Tucson's trails are rocky and unforgiving. I slapped an Eagle AXS derailleur on a rock hard enough to lift the rear wheel off the ground. Damage? Only cosmetic, and I actually heard the Overload clutch do its job.
There's no pushing the lever this far, feeling the mechanical clunk that lets you know something happened and then releasing the lever. I know that we all do that sub-consciously now and it feels like it takes no time or effort at all... but this wireless stuff makes that feel old and slow. Thing is, I don't think it shifts any quicker - it's the same chain and cassette - but the difference between hitting a button and pushing a paddle is more noticeable than I expected on the trail.
I think I'd be just fine if you told me I would be using an SLX or GX group for the rest of my life, but this Eagle AXS stuff is pretty neat. Long-term, we'll see. I have an AXS group coming for exactly that reason, so expect a review sometime in the spring. Questions that need answering include how the group holds up over the long haul, and if it has the metronome-like consistency that an electronic drivetrain must possess for it to make sense in my mind.
Time will tell, but with what we know right now, do you see a wireless Eagle AXS drivetrain in your future?