B Screw Unscrewing

[Dogtrousers]

I have an incredibly minor problem.

I have R7000 105 with a 11-34 cassette. Occasionally changing up out of bottom gear (ie from the biggest sprocket) becomes a bit sluggish. If I don't do anything, after a while the mech starts to chatter a bit in bottom gear. If I still don't do anything, eventually it won't change up at all. The first time it happened I just stopped using the biggest sprocket and left it to investigate when I got home.

The problem is that the "End adjusting bolt" aka B screw is coming undone. No 4 in the diagram below. The solution is to stop, do the B screw up a few turns and carry on. It'll be fine for a few more rides at least. All very minor. Completely liveable-with.

But why? I've never had a this screw undo itself like this before. Should I put threadlock on it or something like that?

 

[si_c]

Yeah, grab some blue threadlock and put it on. That'll sort it.

Most likely it's vibration causing it to rotate out. I have one of the loctite blue threadlock sticks that I just rub most threads on the bike in before fitting. Stops most rattles and issues occuring in the first place.

 

[Cycleops]

And if you don't have any threadlock a bit of Super glue will do.

 

[fossyant]

I'll add superglue if no threadlock. Tiny blob.