SRAM AXS GX Rear Derailleur Intermittent Failure Rant

[s1ammy]

Last September I bought a nicer new bike than I ever expected to, via an online deal that amounted to ~60% off on a Scott Spark 910 TR. I love the bike. It is so much fun to ride.


I would not have chosen electronic shifting, or SRAM drivetrain for that matter, but that's how the bike came and everything else about it was what I was looking for. Last week, mid ride, the rear derailleur stopped working. Totally unresponsive. No lights, no indication of life via shifter actuation, button pushing, or app interaction. I swapped in my spare battery; no change. I rode home charged up both batteries, replaced the controller battery and still no change.

That afternoon I took the bike to a shop, they confirmed the behavior (with both of my batteries and one of their own) then got on the phone with SRAM. Based on this call they installed a battery while holding down the button on the side of the rear derailleur body. Apparently this put the rear derailleur into some sort of mode where it would accept software updates, which they then did. This seemed to solve the problem.

The next morning, rear derailleur is again completely unresponsive. I repeat the battery charging and swapping, now including inserting the battery while holding down the button. Nothing. Rear derailleur seems totally dead. I head off to work with my bike in my van and take it to a different shop (the initial one is in the opposite direction from my house as the one by my work) during lunch. When I take the bike out of the van to bring into the shop though, all of a sudden the rear derailleur is working again. I show it to the mechanic at the new shop anyway. Partway through inspecting it, rear derailleur once again goes unresponsive. So now they have seen it working and not working. This time, when they swap in their own battery it starts working again. So, I leave the shop with a bike that shifts and a new battery and a sense that there is likely something still wrong but no real idea of what to look for.


I email SRAM, relate the entire saga, including pictures (just digital, no autographed, dated, 8x10 color glossies). They suggest I bring the thing to a shop for a mechanic to look at again.


Since then I have 4 rides amounting to ~40 miles total on the system and it has worked flawlessly. I push the button on the controller and it just shifts. Just like it always used to. App shows batteries nearly fully charged.


Now every time I head out, I assume that this will happen again 10 miles into a ride. I like the way this thing shifts, but I really don't like the way it sometimes won't shift. The frame has no holes for derailleur cables, but I am considering zip tying on cables and installing a mechanical rear derailleur. Or maybe I should carry an entire spare derailleur? Has anyone else seen this sort of failure? What do you all do about the inability to actually fix one of these electronic derailleurs on the trail?

[toast2266]

I have no fix for your issue other than to note that, in my experience, the market for electronic drivetrains is very good. I was able to sell a (new) take off GX AXS kit and easily cover the cost of a new in box X0 mechanical setup.

Sent from my SM-S931U1 using Tapatalk

[stuckathuntermtn]

I have no experience with electronic shifting, but I do have some experience with electronics.
It sounds like maybe there is or some was corrosion on other tiny imperfection around the battery terminals or contacts. Perhaps the new battery pushes into the leads better. It's either that or something inside the derailleur's electronics itself. If it keeps happening, it's probably a warranty replacement. If it happens again, no joke, try moistening the battery terminals with breath or a little saliva and sticking it back in. This can cause corrosion in the long run (salt water), or even a short, but it can kinda be like blowing in an old Nintendo cartridge if it's just enough to get the leads to connect properly. Check for corrosion or deformation around the leads in the derailleur, although idk why at least 1 of the 2 different shops wouldn't have done that. Check for corrosion or imperfections around the battery too.

[XXX-er]

We used to use Stabilant contact enhancer on shitty contacts and it was great stuff
I have the cheapest Eagle 70 all steel version of Sram Transmission on my Eeb and I like it, I had to learn to trust it to shift anywhere, I'm pumping 100NM thru it now so we will see how that goes

[davjr96]

Take a look at the little metal contacts on the derailleur, they are basically little pogo sticks. They have a spring inside that pushes a probe into contact with the terminals on the battery. I have seen that spring wear out causing the contact with the battery to not be made or be intermittent at all. This is inspectable by comparing the derailleur contacts with a charger. Press down with your finger or something on the contacts and see if you can feel the spring/if there is any friction pushing in and out and compare it to the sticks on the charger.I had one of the pogo sticks die on my derailleur, I fixed it by getting a cheap charger, taking it apart, unsoldering the stick, and then replacing the one in the derailleur which was accomplished by removing one screw and then a bit of soldering.