My FF has developed an automatic speed limiter in that when I get to 75 mphish the right mirror folds in on itself! Very clever 
I wondered if anyone had any suggestions on a good replacement - I know the 10mm fitting is pretty standard and having mirror longer arms/ bigger mirrors would help visibility.
LOL mine used to do that too above about 120mph, for some reason seems to only happen when BIF borrows the bike…
Loctite threadlok does the trick!!
Should have explained its the mirror swivel socket that is the problem not the thread on the shaft itself. I found some with a longer arm to mirror on e-bay for £20 They may also let me see a bit past the old elbows. cheap enough so I’ll tell you how we get on.
I need to swivel the whole mirror arm in to get though our gate.
I bought some pattern ones from Wemoto for my FF when the stock ones went all floppy on me.They look just like the stock ones but stay where you put them.About £30 i think but well worth it.They do cheaper ones that dont look like stock as well.
Well those e-bay ones are highly recommended! The extra length certainly help visibility and the simple design goes well. I will move the bar forward next to ease the wrist strain.