I have 1x9 drivetrain setup on my Giant Seek.

Components were Superstar XCR chaing guide, Deore derailleur long cage, SS FSA chainring.

Few days ago I put Sram X7 medium cage derailleur and the rest of the setup is same but chain keeps falling off

Chain length is OK, new derailleur is not bend, everything seems to be ok but it's not...

Any suggestions?


Old setup (no problems with chain, never!)



New setup

You should probably post this in the "bicycle mechanics" section.

Check your derailleur alignment/adjustment. Something doesn't look right on the x7, can't tell though from my phone screen.

You didn't say if it's dropping off the front or rear. But as you only touched the rear I assume it's happening there?

Are your limiters adjusted correct? When I adjust them I have the chain off, push the derailleur across to the big ring by hand and see if your jockey wheels go past the biggest chain ring. If they do adjust your limit screws so they line up. You can use the derailleurs spring to line up with the small chain ring.
If while riding your chain has trouble getting onto the smallest or largest ring readjust the limiters so the jockey wheels go just a fraction past the chain rings but you can fine turn that too while out riding in very small increments being careful not to go to far so the chain comes off again. Hope this helps.

Shorter cage would've slacked the chain a touch. Check your chain length. Then check to make sure the limit screws are set proper. Also the B screw. Some higher-end derailleurs tuck in tighter for more off-road clearance.

Thank you all for comments and suggestions

Well as somebody mentioned I didn't say that it falls off on the front which is almost impossible cause of the single chainring and chainguide... so I take a closer look and find out that chainguide was to low and pushed the chain out of correct aligment in some gears.

Readjust the guide and problem solved....everything works fine again