John wrote: The diameter of the tire being ever so slightly
> larger may improve mileage a tiny bit, as well as making speedometers
> read more near acurrate. (typical vanagon speedos being 5 mph short of
> reality whne cruising at highway speeds).

John, a larger diameter tire is going to make the speedometer indicate
lower, not higher, fewer revolutions per mile.  In addition, I believe
that the 'Vanagon speedos read low' is not always true.  On both my
'85 and now my '90, with 185R14 tires, the speedo was nearly dead on
at 60 as close as I've ever been able to measure on measured stretches
of freeway with a stop watch or with GPS.  The odometer shows about .1
long in five miles indicating about a 2% error or about 1.2 mph at 
60mph.  Given variations in tire pressure and human error in taking
the readings this is well within the error margins I'd expect for such
crude measurement.