On Wed, 19 Jul 2017 22:33:56 -0400,
wrote:

Not necessarily - a 10 spoke alloy rim will weigh less than the
typical 5 spoke, because there is less aluminum there. Also, a rim
with more open space wighs less than one with more - to the point my
16 inch torque thrusts weigh less than my 14 inch deerfoots.

I am not at all disagreeing with you that different rims weigh different
amounts where size isn't the only determinant of the weight.

I never disagreed. I'm just trying to control the variables in this thought
experiment because I was trying to figure out what the benefit, alone, was
of larger-diameter fitments.

Does anyone know if, apples to apples, you increase a rim by one inch,
whether the decrease in sidewall rubber compensates enough to counteract
the gain in rim weight?
Depends on the tire. With an LT tire, likely. With a "performance"
passenger car tire, likely not

Thanks. I didn't look up the density of the rubber versus the metal, mainly
because the volume matters greatly and I would have no weigh of knowing
that for this thought experiment.

It seems from most of the referenced articles that, realistically, there's
no change in gas mileage for an inch change in diameter simply because of
all the other factors involved in the real world.
With one inch, likely no net loss - with 3 or 4, almost definitely in
city driving.

I have to agree with you that the two reliable articles that referenced
four inches of change all showed (and expected) huge losses in performance.

None of the articles seemed surprised at the losses, although the consumer
reports article discussed that the measurements were such that they were
within their measurement margin of error.