lug nuts

Okay, got home from Wyoming and found a tire quite low on
pressure.  Did the cleanup and it's definitely flat.  I got the
thing jacked up and tried loosening the lug nuts--but failed. 
After many tries, I think the socket I have (13/16") is just
slightly too big.  It wobbles a bit when placed all the way in.

A 3/4" won't go on the nuts, so maybe I need metric?  Seems 20 mm
would be the size just less than 13/16".  Does that make any
sense?

My bigger concern is that I'v probably rounded off the nuts from
trying too many times to turn them with the socket I have.  Any
suggestions on how to go at this?

--
Ted Heise      <theise@panix.com>       West Lafayette, IN, USA