Wheel offset.

[Gene Fox <genefox@bellatlantic.net>]

Here we go.   I'm about to change the wheels on my 80 MG roadster.  The
move is from 14" to 15" rims with 185-195  65 series tires.   My
question to the group..   What is the offset (plus or minus in mm) I
need  for new rims? I'm going to have to make an adaptor plate for the
new wheels but can't find any printed information on what the actual
offset is on the MG rim.   Is it  the same in front and rear?  Being
inherently lazy if you know it in inches could you convert this to MM
for me. Thanks in advance.