I know there was a thread from 09 or something but I thought I would add my 2 cents.I have a three wk old 2017 wee and the left mirror was bugging me and needed tweaking. I tried to adjust it not knowing about the lft hand threads althouigh It did occur to me but it was so tight by this time it would not go either way. After seeing the post about the lft hand threads I gave it another try. Here was the problem .The mirror was not a tight fit for a 17mm open end wrench.I have a set of ones that go 3/4 around and even that one was not tight enough to prevent rounding it off.So I took a large adjustable wrench which is usually the last thing you want to try in this situation.But I used a pr of channel locks to tighten it. In all these yrs I dont think I have ever taken a pr of channel locks to a adjustable wrench thumbscrew. Worked like a champ and was able to free it and adjust it .