Ok, this is kind of embarrassing.
My 2006 DB9 Volante owners manual tells me that if my car has 22mm wheel nuts I should torque them to 100 lb/ft, but if they're 21mm they get torqued to 130 lb/ft.
I don't know which they are.
My biggest metric socket is 19mm, so I've always used a 7/8" socket on the nuts (a 13/16" is too small). 7/8" converts to 22.2250mm while 13/16" converts to 20.6375mm. So that means that both 21mm and 22mm slot in between 13/16" and 7/8".
I'm GUESSING that they're 22mm because 7/8" is a pretty good fit and I think 21mm would be too sloppy...but does anyone know for sure?
Thanks.

 

... 115lb to compromise then

 

I had this same issue when I took my 2007 DB9 to get new tires last week. The tire shop didn't know initially so I was pleased I did the research beforehand to be able to tell them.

The answer is that on the DB9 wheels, the nuts are 22mm and should be torqued at 100 lb/ft or 135 Nm.

The 21mm I believe are for the Vantage.

Page 13.6 on my Owner's Manual.

 

Thanks, Ken!