Which reminds me of a joke....
A Texan is traveling through NYC and around lunchtime, sees a deli and decides to give it a try. He sits at the counter and when the counterman (Murry.... it works good when the deli guy is Murry..... or Saul.... or Benny) asks what he wants, the Texan says he has no idea 'cause he has never seen food like this and does not know what he wants. The server says "Well, tall ya' what: here is a nice bowl of matzoh ball soup that you can try. Look around and maybe you will see something you like." A bit later, Murry comes by and asks the Texan what he thinks, to which the Texan replies: "Hey, that soup was pretty good..... anything else on dem dare matzohs you can eat?"
Ba Dum Dum
Now back to the nuts on the bike.... Yep, that axle nut is absolutely metric and not SAE although I don't remember the size. I also use a close SAE socket to remove / install it because that is the closest thing I have to that size and I do not have anything that large in any metric sizes.
If you want to do yourself a favor, stop by Home Depot, Lowes or a hardware store and pick up a hitch pin to replace the cotter PITA pin that comes through stock. The hitch pin is easy, fast to use and just as secure IMO.
Brian
aahhh nuts...