SRAM's Transmission groupsets, whether that's the electronic AXS versions (S1000, GX, X0, XX and XX SL) or the newer Eagle 70 and Eagle 90 mechanical versions, have market-leading shift performance.
Up or down the block, under power, on an electric or regular mountain bike, the shifting is crisp, accurate and utterly dependable.
Most of the time…
However, there are instances where the shifting isn't up to spec.
With no adjustment screws – B-tension, Hi or Lo – it might not be obvious what's gone wrong.
Behind the scenes, though, SRAM's Universal Derailleur Hanger interface has made life without such adjustment screws easier, because the gap between the cassette and the dropout is much more defined than before.
As such, as long as you once had good shifting, there's a good chance a fix is far easier than you'd think.
I've suffered poor shifting with my SRAM Transmission drivetrains, but I've also worked out what's wrong and how to fix it. So, here's my step-by-step guide to solving your Transmission trouble.
Step 1: check your setup
If your drivetrain came fitted to a bike, this step should be sorted. However, if you purchased your own Transmission groupset to fit to a frame, check your setup was done correctly.
The correct chain length and use of the right Setup Key and Setup Cog are required for smooth shifting.
The SRAM AXS app and SRAM’s online Full Mount Chain Length Guide will define this for you, once you input your bike’s model, size and chainring size.
Double-check this has been done correctly.
Step 2: are things running smoothly?
Before delving into the derailleur itself, make sure the chain and cassette are in good condition.
Check there are no stiff links in the chain by rotating the cranks backwards and watch whether the derailleur’s cage snatches forwards, or if any links roll awkwardly over the jockey wheels.
If so, gently flex the chain’s link laterally until it articulates freely, and clean and lubricate it properly once home.
Ensure there is no debris caught between the cassette’s sprockets that might interrupt the chain's smooth progress over the teeth.
The cage of the derailleur will look as though it has been bent, however this is the usual form of the cage. If it is significantly bent, though, this could be causing your issues.
Step 3: check your alignment
If the setup was done correctly, and the chain and cassette are sorted, the likelihood is the body of the derailleur and the silver knurled ring that sits inboard of the frame, between it and the derailleur, are misaligned.
Both the derailleur and silver knurled ring have marks on them, which need to align for smooth shifting.
These can misalign when the rear wheel is put back in after removal, or if the derailleur has shifted on the dropout – either due to the wrong torque being used or because it has suffered impacts.
Have a look – it's likely that these two marks will no longer be aligned.
Step 4: rear-axle woes
The most common issue is when the rear wheel’s axle is tightened before the derailleur is positioned correctly.
When the rear axle is loose, the derailleur can swing forwards and back, but it becomes fixed in place when the axle is tightened. If it is tightened when the derailleur is not returned to where it should be, issues can arise.
To remedy this, with the derailleur in its fully extended Open mode (using the Cage mode button to lock it in place), loosen the axle and push the derailleur body forward until it hits the stop. The lines on the derailleur and silver knurled ring should align.
Then, tighten the axle and check your shifting.
Step 5: derailleur re-set
If this doesn’t solve your issues, it is likely the derailleur and the silver knurled ring have rotated in the frame’s dropout, altering the relative position of the top jockey wheel and the cassette.
To fix shifting now, you will need to put the derailleur in the cage setup position, as defined by SRAM for your bike. Push the cage forward a little and depress the Cage mode button.
Loosen the wheel's axle by one full rotation, and loosen the derailleur’s mount bolt so the derailleur and silver knurled ring are able to rotate.
Step 6: tension time
Pull the derailleur back so there’s a moderate amount of tension on the chain, and check the silver knurled ring has also rotated back, aligning the two marks.
In some instances, you might need to use a small Allen key to move the silver knurled ring back into alignment.
Step 7: trailside tightening
The mount bolt can then be tightened up. It needs to be tightened to 35Nm, but on the trail with a multi-tool, this just means pretty tight.
If you over-tighten it, you may cause damage, but if you under-tighten it, the system may slip again. It is tighter than the bulk of the other bolts on the bike, though.
Your rear axle might also spin as you tighten the mount bolt, so if you're riding with a friend, it might be useful to use a second multi-tool to keep the axle stationary while the mount bolt is tightened.
The rear axle can then be tightened. Likewise, the correct tightness is important for overall performance. However, if you don't have a torque wrench, tighten it to your usual level with a multi-tool.
Step 8: complete the job at home
When you’re home, return to your bike and re-set the system properly to avoid future issues.
It is worth taking the derailleur off the bike and removing the bushing frame insert from the frame’s dropout.
Give this, and the dropout, a clean and replace in the manner it was removed. Do not grease it – it must remain grease-free.
Replace the derailleur and follow the setup process again, referencing the SRAM AXS app or SRAM’s online guide.
The mounting bolt should be torqued to 35Nm, and the rear axle to your manufacturer’s recommended settings.
