I'm trying to get the knock sensor out of the FD, but all my wrenches are too small => I need to buy another. This thing is so out of the way that it's tough to measure so I'm not 100% sure of the wrench size I should buy. I think it's 25mm. Can anyone confirm?

Ta

 

It's somewhere around that size. I just use a large adjustable wrench.

 

I can't remember, have you tried using a big crescent? I know its not 22 or 24, since I happened to have those the other day. Good luck, Josh.