i have a question about fitting tires to wheels.  wheels seem to be
specified based on a diameter and width, both in inches.  matching the
former to a tire is simple, obviously, but how about the second?  if i
have a 15x6.5 wheel, what widths of tires will it fit?  will a 225 be
too wide?  a 185 too narrow?  will a 205 that fits on my 6.5" wide wheel
also fit on a 6" or a 7"?  or is every given tire built specifically for
one exact tire width?  if not, what are the performance implications of
mounting a given tire on a wider or narrower rim?

thanks!

Ben.