Hi, was removing my Derailler for travel and undid the 2nd Allen from the top. Which I now know wasn’t right. What does this do?

Nothing to worry about, it’s the pivot for a Shadow type mech (older mech’s pivoted at the frame), and can be removed to replace a damaged dog-link, or for fitting to one of the direct-mount type frames that are now beginning to appear on the market.

Thanks. It seemed to loosen but not undo. I realised I had errored and undid the top Allen bolt to remove Derailler.

When I refit the Derailler how tight should the 2nd Allen bolt/pivot be? i.e. Is it a bolt that sets something (like a limit screw) or a bolt that holds something (like, re, most bolts)?

Does it effect the tension/resistance or operation of the Derailler?

Many thanks.

It’s held in with a circlip behind the pivot, so won’t come out completely without it being removed first.Clearances are all preset, so you can just tighten it up.