Rail 5: Chain dropping from chainring

[Hamina]

What might have happened or should be done: Yesterday the chain started to drop from chainring out to the pedalside. I tried to google around a little didn't find or understand any good solution.

Any good tips where to start? It seems to happen when I have the smallest cog on. Is the chain too long? Chain tension too low? Chainguide in wrong position or bent? Chain wear too much? (450km)

The original SX derailleur has been changed to GX.

 

[Philly G]

I would check the lockring that holds the chainring on is tight. Common issue with it coming undone. If it's starting to come loose, the chainring will have lateral movement , and when you're in your smallest cog, the chain will be at it's slackest, so will be most likely to drop. This could be the problem. It will be a process of elimination, check over every part of the drivetrain until you find the issue

 

[BobBuzz]

I´ve been having this problem with a Trek Rail 5 2022. Seems that e*thirteen have recognised that there is a problem and suggest a 1mm spacer to fix this:

Look here: https://support.ethirteen.com/hc/en...T-ON-E-THIRTEEN-E-SPEC-STEEL-BOSCH-CHAINRINGS

Really annoying and i have had to replace one chain already.