SRAM AXS Drivetrain: Trail-Proven Wireless MTB Performance

Electronic mountain bike shifters, wireless mountain bike droppers… Here we are in 2022, and the rise of electronic bike components is steadily taking over.

But is it worth it? Is it reliable?

Just a few short years ago, we were among the skeptics, but SRAM AXS continues to impress!

We've put SRAM AXS through the rigors here in Sedona, Arizona - from rock bashing to techy-uphill-over-loaded shifting - and can genuinely vouch that SRAM AXS is trail-proven.

Of course, the aesthetics of wireless and ease of installation without having to run cables internally through frames was always going to be a clear advantage. What we've been most interested to see in the long-term is its durability… especially for the cost of getting into an AXS groupset and for how rough our favorite trails can be on components.

With our review, we aim to give you an overview of the AXS family and why we've come away impressed. 

AXS Upgrade Kit Unboxing

Like all SRAM components, unboxing the kit is an experience! The packaging is top-notch and nicely laid out.

SRAM has three tiers in their hierarchy of AXS upgrade kits: XX1 at the top, followed very closely by X01, and then GX. Luckily, all 3 of these Eagle AXS upgrade kits share many similarities with the same amazing performance; the difference is just in the small details.

That's great news considering that all three kits aren't exactly a cheap upgrade!

Looking at the similarities, all 3 AXS upgrade kits include everything needed to convert your bike to wireless shifting - AXS derailleur, controller (shifter), battery, and charger. All three kits use the same battery and charger, too.

They're all cross-compatible and use the same SRAM AXS App to customize shifting and make adjustments.

Another nice bonus is that all three levels of AXS offer the same motor in the derailleur, along with the same overload clutch feature. This feature is the crucial ingredient that makes the AXS derailleur durable and able to take hits that would tweak a traditional derailleur. 

Sounds great, right?

Let's move on to those small differences - this comes down to component weight and intended riding category - cross country, enduro, and trail value.

XX1 is the most expensive for a reason, and that's because it's the lightest weight of the three upgrade kits. It uses titanium hardware and carbon pieces in the derailleur to trim every gram possible, making this group competitive for that cross country race category.

X01 is just a tad heavier and a bit more durable, with stainless steel hardware in the derailleur. This balance of weight and durability is ideal for enduro and down country riding.

GX uses steel hardware in the derailleur, giving it a minor weight penalty but retaining the same performance. We like to think of GX as the Trail Value version, capable for aggressive trail riders at a more affordable price. 

SRAM AXS Shifter (MTB & ETAP) 

When it comes to the AXS groupset, controller = shifter!

This can be confusing, since shifters have always been called, well, shifters. However, to highlight the new tech, SRAM has opted to specify their wireless mountain bike shifter as a "controller."

XX1, X01, and GX use the same controller body and battery, and surprisingly, all weigh the same.

The upgrade for XX1 and X01 is the ergonomics, using a "rocker paddle" that feels more like a traditional mtb shifter. GX has the original AXS paddle that's slightly bulkier but easily gets the job done.

Luckily, if you prefer the more classic feel, the rocker paddle can be purchased separately and added to your GX group for $20. Check out SRAM's Rocker Paddle Upgrade Kit here. 

SRAM's ETAP line generally refers to their wireless road bike group, which we won't get into since our focus here is mountain bikes! 

SRAM AXS Wireless Derailleur

The AXS derailleur is really where the magic lies, and in our minds is the crucial piece that would make AXS worth it or not. This component needs to work perfectly every time. Otherwise, it's not worth the extra cost to go with AXS.

Add in the super high cost of AXS derailleurs; it would also be hard to justify going wireless if these derailleurs can't survive rock hits or miss shifts.

Amazingly, SRAM has accomplished a design of this derailleur that's exceptionally robust and stronger than traditional derailleurs! 

How did Sram do it?

For durability, the key feature is the Overload Clutch.

This allows the derailleur to protect itself by moving inward when it takes a hit and automatically reset itself back into place. As a bonus, this ends up protecting the derailleur hanger, a piece that is traditionally designed to break in order to save the derailleur. 

For precision shifting, Sram designed a small electric motor capable of extremely high RPM's.

These RPM's provide the torque for the derailleur to move and shift gears under load. Considering how tiny the motor is, the torque produced is tremendous. Each shift makes an audible 'zzzzst' noise, and moves the chain the exact amount needed every time.

It not only sounds precise, it is precise! 

AXS Wireless Dropper Post

The time has finally come!

Rockshox's Reverb dropper post has long been overdue for a redesign. In fact, it's over a decade overdue!

Here at Thunder Mountain Bikes, we've had more than our fair share of frustrations and disappointments with the old Reverb.

One of the big issues was the hydraulic line to the actuator, which could easily kink inside the seat tube, causing inconsistencies with the dropper. Granted, this can happen with all droppers, but the Reverb was especially prone.

A great way to fix this is simply getting rid of the cable/hose. Easier said than done… but SRAM has finally done it with AXS technology!

We thank and salute SRAM for making this work so well! 

Like the AXS drivetrain, this wireless mountain bike dropper post houses a battery, motor, and a similar controller.

The motor and controller give the dropper action a fast and 'zzzzst' precision feel.  The battery is conveniently cross-compatible with the drivetrain battery and mounts just under the back of the saddle.

Getting rid of the cable/hose has made this dropper so much more reliable.

In addition, the vent valve feature has been vastly improved, making it accessible without removing the saddle. This feature allows the rider to quickly fix any sag in the dropper on the fly.

While this AXS Reverb is the most expensive dropper post on the market, we feel it's living up to the price tag.

Want more control? There's an app for that!

As expected with all electronic devices these days, there's an app to give you complete control. With SRAM's AXS app, you can customize the feel and function of the AXS components.

Want the shifter to make multiple shifts by holding down the controller?

Adjust that in the app!

Want to reverse the shift directions on the controller?

Adjust that in the app!

The app also conveniently shows battery charge levels, delivers firmware updates, and reminds you when you need service. And these service reminders aren't just based on general time spent riding. It delves deeper where the AXS components store the actual shift counts, rotations, etc. The app uses that data to suggest service recommendations. 

One of the great things about this app is that you don't actually have to use it.

It would have been easy for SRAM to force users to depend on the app, but thankfully they realize this can affect your ability to simply ride your bike.

You can unbox the group, install it on your bike, pair the shifter and derailleur, and never need to download the app. You can even make derailleur adjustments without needing the app.

SRAM didn't want your ability to ride your bike to depend on an app or having cellular data, which we couldn't agree with more! 

Overall Pros & Cons Of An AXS Upgrade