I just faced changing my tyres and as roads around here are poorly maintained toyed with the idea of going to 18" from my 19". The tyre price was also nearly A$170 cheaper with the smaller wheel. However, the OEM wheels are much too dear and the selection of after market with proper offset wheels (without spacers) is near nil so this was a quandary.
My tyre shop came up with what was the obvious answer - step us to a 245/40 19 instead of the 235/40 19. The actual circumference difference is only about 1% greater but the sidewall grows a bit more, and slightly larger contact area. And, best of all, the tyre cost drops dramatically - actually to the same savings as the 18"! Why 235's are so much more I don't understand...
Anyway, happy to report that the ride has improved significantly. Partly due to the tyres (now Michelin Pilot Sport 3 instead of Conti) and the rest if not most due to the tyre size. Over the same road surfaces quieter and the jarring has gone but not to such a large extent to affect grip. Not the way I drive anyway.
So while changing tyre size may seem strange - even blasphemous - in this case I believe the results were well worth it.
Oh, and one of the old tyres sans rim is now sitting in the wheel well (fits nicely). Not as practical as with a rim but not as heavy and if I get caught somewhere at least I can reduce my costs to a tow and tyre swap until I get sort out a new tyre.
