SRAM Eagle AXS Backpedaling Issue
 

Hey everyone -

So I finally got around to installing my SRAM AXS Mullet (Force Shifters / GX Eagle RD) on my Stigmata. I bought everything new (shifters, rd, cranks, chain) except for the 10-50 cassette which I bought "lightly" used. That cassette shifted horribly, so I figured it was worn, the seller lied to me, whatever. I bought a brand new cassette today and the shifting is way better. However, I cannot seem to backpedal in the 10T cog without the chain skipping all over the place.

Here
What could be causing this? B-tension was set using the SRAM tool that comes with the RD, limit screws are set fine and when pedaling forward it sounds pretty quiet (a bit of clicking but I imagine that is inevitable with a 1x12 setup). RD hanger is straight. What should I look for / adjust?

Maybe too obvious but have you tried indexing a little bit more outbound? Make sure to back the high limit off a hair so it can move out a hair. Also have you checked if the chainline is way off or mismatched?

Please explain to me how making ANY adjustment at all to the rear derailleur will help solve this problem. I'll wait.

If the guide pulley is centered towards the centerline of the bike relatice to the 10t cog it might explain op's problem. I admittedly don't test for such aggressive backpedaling but most eagle drivetrains can back pedal on the 10t, its the largest cogs that sometimes can't back pedal. What do you think is up with op's dt?

Op: Did you check the orientation of the connecting link?

Don't backpedal in the 10t. The only variable that will change the backpedaling performance is changing the chainline. The rear derailleur has no bearing on this, being placed after the cassette while backpedaling, it is no longer guiding your chain to the cassette. Your chain is skipping because nothing is guiding the chain off top of the front chainring to the top of the 10t cog while backpedaling. It is an extreme angle for the chain to take, and it wants to take a smaller angle, so with nothing to guide it out further, it catches on the next inner cog.
Solution is to not backpedal.

Yep, chainline is the problem. Either don't backpedal in that gear or find a way to move your chainring outwards, but that might be difficult and introduce more problems, so I'd go with the former solution - avoid backpedaling in that gear.

Pedaling backwards. Nothing you do at the derailleur will change what's happening when you back pedal.

This makes sense. I stand by my chainline guess--my guess would be a road chainline crankset with a mountain chainline derailleur/cassette. If you have a choice, OP, you may be able to simply change to a chainring with less offset.

If change the chainring offset to favor the outermost cog, you will screw up the chain line to the innermost cogs. This is a 1x, right? The chain line is correct when the chain is parallel with the centerline of the bike when it's on the center cog on the cassette.