Installing SRAM's Eagle AXS wireless electronic drivetrain believe or not is a piece of cake. For tools, you will need a cassette tool, an 8mm hex wrench, a 5mm hex wrench, a 3mm hex wrench, a T25Torxx wrench, a chain breaker, and a T8 Torx wrench. We will also be using a 3-way wrench with a 5mm and T25 on it as well. If you are buying a new SRAM Eagle Rear Derailleur or full SRAM groupset, then it will come with the b-tension tool, but if you do not have that you will also need one of those tools. For shop supplies, we will need some assembly grease and rubber gloves.
Now let's dive in and take a look at what comes inside the full SRAM XX1 Eagle AXS groupset. On the top layer, we've got the beautiful oil slick XX1 12 speed chain, the non drive side crank arm and crank spindle, the XX1 Eagle AXS controller (shifter), a super slim SRAM multi tool, one eTap/AXS battery pack for the derailleur, the handlebar clamp for the controller, and the battery charger and charging cable. In the 2nd level of the box you'll find the drive side crank arm and chainring, the derailleur, and Eagle AXS b-tension tool. You may be familiar with the red b-tension setting tool that comes with other Eagle derailleurs. The blue b-tension setting tool that comes with Eagle AXS is specific to AXS derailleurs so be sure to use the correct tool. At the very bottom of our box is the crown jewel of SRAM's XX1 Eagle AXS, the full oil slick XG-1299 10 to 50 tooth cassette. Now that we have everything laid out, let's get into it.
This video/article will be covering how to install a full SRAM Eagle AXS drivetrain, that includes, Cassette, Crankset, Rear Derailleur, Controller, & Chain. We will be going through installation steps so at the end of this you will be able to fully set up and ride your new bike with wireless AXS shifting. Once you have all of your parts that you are installing out of the box and ready to be installed we are ready to go. If you are only installing a AXs upgrade kit with just the Rear Derailleur and Controller then you don't need all these steps and can probably only refer to steps 3, 4, 5, 7, 8 & 9.
Remove your wheel from the bike and apply a layer of grease on to the threads of the freehub body. Set the cassette on the freehub body and tighten it down with your cassette tool. Make sure you start tightening the cassette square with the wheel to avoid cross-threading. Also, make sure you tighten the cassette to a full hard stop, some cassettes, often SRAM GX Eagle, starts to get tight but are not fully threaded on, this can cause the 10t smallest cog to make contact with the frame once installed.
For this particular mountain bike How To, we already have the bottom bracket installed. If you want to get up to speed on installing your bottom bracket, check out our article How To: Install SRAM Eagle DUB Crankset and Bottom Bracket. Apply a thin layer of grease on the crank spindle and slide it through the bottom bracket. With all SRAM DUB bottom brackets, be careful not to knock out the drive side plastic cover when sliding the crank spindle in to place. Use a 8mm hex wrench and tighten the drive side crank arm and chain ring on to the spindle. To remove all of the play from your cranks, turn the preload spacer to snug up the cranks. Be careful not to over tighten that preload spacer and then tighten the pinch bolt using a T8 torx wrench.
Before to toss the derailleur on, be sure to put on some rubber gloves. Oils and grease are bad for your skin! Put a small dab of grease on the threads of the derailleur and thread it on to the derailleur hanger using a 5mm hex wrench. Now we will grab the controller and install the controller on to the handlebar. We will be using a SRAM Matchmaker-X for a nice and tide look on the handlebars.
The battery comes out of the box with a battery cover on. You can now pull that cover off the battery itself, and then also remove the batter cover from the derailleur. Set the battery into the derailleur and lock it in to place with the latch.
Just like pairing your phone with a bluetooth speaker, your SRAM AXS derailleur and controller must be synced together. First press and hold the AXS button next to the battery on the rear derailleur until the small light on the derailleur begins to flash green. Now go up to the AXS controller / shifter and press and hold the button on the underside of the controller until the light on the controller flashes a few times. The derailleur and controller are now in sync. Now go back to the derailleur and push the AXS button one time to tell the derailleur to stop searching. You should now be able to shift gears using the controller. The same process would be done if you are also trying to pair your drivetrain and Reverb AXS dropper post, the steps would start at the rear der, and then shifter controller, Reverb controller, Reverb post, and end back at the rear derailleur.
Last but not least, now it's time to install the chain. All SRAM Eagle chains are not directional unlike Shimano chains. Route the chain through your derailleur, cassette, and chain ring keeping in mind that both the chain ring and derailleur pulley wheels use a narrow wide design. Now it's time to cut your chain to length. For a full walk through on installing a chain, check out our How To: Installing A New Chain For Your 1X Drivetrain. Be sure not to cut your chain too short or as you go through your suspension travel, you run the risk of damaging your drivetrain. Set your chain and derailleur in the smallest cog on the cassette and cut the chain at the first available link that pulls the derailleur in to tension. Now install the SRAM chain power link. The power link / quick link is directional so be sure to install it properly. The arrow on the outside of the quick link should point in the same direction that chain travels while pedaling. Make sure that the power link is fully snapped in to place.
Setting the B-Tension is extremely important for SRAM Eagle 12speed, it’s much more sensitive and needs to be adjusted in sag as well. Once you have your chain on, and rear der shifting, shift into the second to largest cog if you are using the new Sram Eagle B-Tension tool, take a look at the photo below to see the older style and newer style. The good news is that the newer style works for all Sram Eagle Ranges, 10-50t or 10-52t. Once you are in the second to largest cog, you will need to adjust this in sag, so you might need a friend. Once there, place the upper part of the b-tension tool on the 50t or 52t and then rotate the tool and cassette so that the lower part of the tool sits on the upper derailleur pulley. You will notice there is a small window on the B-Tension tool, its a circle with a point in the middle of it. Once the tool is both placed into the largest cog, and then resting on the upper pulley wheel, that point in the small circle should perfectly line up with the upper pulley wheel bolt. Either add or remove tension to the B-Tension bolt to make sure that the upper pulley wheel sits perfectly into that window.
Adjusting the limit screws on the derailleur will keep your shifting quick and precise. The limit screws are tucked right underneath the AXS battery pack on the derailleur. The low limit screw which is the right of the two set screws adjusts the low limit or biggest cog. The high limit screw is the left of the two set screws controls the high limit or smallest cog. This may seem a little bit counterintuitive so be sure to follow along in the video above. Start with the high limit screw and adjust the set screw until the chain is spinning smoothly in the smallest cog. Then work your way up to first gear and do the same for the largest cog. Make the limits as tight as possible while still allowing the chain to jump into 1st and 12th gears without any skipping, or jumping around.
If you are having trouble getting your chain to shift down in to the smallest cog, this is where the micro adjust comes in to play. Think of the micro adjust feature just like a barrel adjuster on a traditional cable actuated derailleur. To access the micro adjust feature, press and hold the button on the bottom side of the controller and press the controller paddles two clicks at a time in the direction you need the derailleur to adjust. So if you are having trouble getting the chain to drop down into the smallest cog (12th gear), click the downshift paddle when you are in the micro adjust mode.