I wasn't arguing
Anyways, my Irmscher Stila 18" wheels have an offset of ET33, but Irmscher Sportstars have an offset of ET30.
Both are Omega fitments, so whichever spacer you can find more easily will be fine
Note, with some tyres you can get away with an offset of ET38 with 8J 18 wheels, but they can rub on the front struts, so aren't recommended...
You will find that 225/55/16 and 245/40/18 are the same rolling radius. 235/45/17 and 235/40/18 are almost the same rolling radius...
Incidentally details of the official factory tyre sizes for the facelift can be found on pages 227 and 228 of the Owners manual, here...
http://www.omegaowners.com/forum/index.php?topic=90477.0The official 18" tyre sizes come from Irmschers certificate of conformity supplied with the wheels when new
Factory wheel/tyre sizes depend on engine size and spec, but all Omega Bs from '94-'03 have 195/65/15 spare wheels as standard.
Facelift cars had the following...
Four cylinder, including diesel...
195/65/15
205/65/15
225/55/16
235/45/17
All V6s...
205/65/15
225/55/16
235/45/17
Pre facelift cars had the following...
All four cylinder...
195/65/15
205/65/15
225/55/16
All v6...
205/65/15
225/55/16
235/45/17 MV6 only, '97-'99.
Hopefully that answers your wheel/tyre questions