I'm going to jump in on this 'Power Loss With Larger Wheels' thread with a
real world comparison.  Last fall I spent about ten days running around NE
Oregon with another Westy.  I'm driving a '90 Westy with 14" alloys,
Michelin Agilis 185R14 tires.  The other was an '87 Westy running 16" wheels
and tires, Nokians, don't know the exact size.  Both running well
tuned 2.1LWBX engines, both with automatic transmissions.  We were
gassing up at the
same time.  And we were driving a lot of up and down and around curvy stuff
in the hills around John Day and up into Hells Canyon.  Results:  At a
couple of fuel stops we were within a tenth of a gallon of the same
consumption.  On at least one leg I had better mileage, on several others
the 16" had better mileage, once by over a gallon.  The conclusion I had to
come to is that it wasn't making any significant difference, 14" vs. 16"
wheels.  We easily kept up with each other on the hills, up or down.  One
thing I did notice was that downhill, when I was following, was that with
the foot off the gas, coasting under gravity, I always tended to overtake
the other Westy and had to brake to keep from overrunning.  Maybe
significant, maybe I have a sloppy torque converter, I don't know.
All this contributed to just confuse the whole issue, but a Feynman type
answer.