Riding along a quiet road at around 70mph, all of a sudden the right wing mirror swings right back. I mean the whole mirror arm. Pulled over to the side of the road and spun it around, thinking that would tighten it but it didn't, it just kept going round freely. So worked the little rubber cover at the base up far enough and tightened the bolt as tightly as I could by hand, which so far seems to have done the trick. I blame the pigeon that hit the same wing mirror on the same road last year.