On Wednesday, July 19, 2017 at 3:27:57 PM UTC-4, Mad Roger wrote:
On Wed, 19 Jul 2017 12:13:37 -0700 (PDT),
trader_4 wrote:

The problem is that you don't understand the physics.

I am not going to disagree with you.

That's why I want a reliable reference that backs up any claim of better
gas mileage with a larger diameter tire.

This article from Cooper Tire says that our intuition is wrong for example.

You keep saying "our intuition" when it's clear that both Bob F and
I don't agree with your intuition.




Do larger tires improve gas mileage?
http://www.dunntire.com/blog/Do-larg...ve-gas-mileage

"The common belief is that a tire with a larger diameter will cover more
ground per revolution, thus reducing overall gearing and enabling the
engine to run at lower revolutions per minute (RPM).

That's not belief, it's fact. Assuming of course that you do change
the gearing.




People generally
associate lower RMP with less fuel used to travel the same distance.

Maybe they do, but it's not correct. Following that logic, you
could bog an engine down into the low RPM range and with it
struggling, it would use less fuel, even with the throttle wide
open.



While
this may be true in a few instances, it is not the case for most vehicles.
There are too many variables to make a universal statement that larger
tires are more fuel efficient."

They then explain that the torque curve is critical, which makes the
equation too complex for a Usenet discussion instantly (because of the huge
number of variables involved).

But you're the one making the incorrect and simplistic assumption
that less torque means less fuel used.




Now you're just deliberately throwing obfuscation into the problem.
Sure there is more wind resistance at higher speeds. But you were
talking about a car moving at the *same speed* down the highway
and saying that it involves more or less energy because of differing
torques.

Huh? You misinterpreted what I said

I didn't misinterpret anything. I gave you an example of where you
can ride a bike up a hill at two different gear ratios and with
the lower gear ratio, it will take less torque at the pedals, but
the energy used is exactly the same. You then proceeded to throw
another variable in, going up the hill at different speeds and
the effect of wind resistance. The car example you keep bringing
up, you're talking about different diameter tires, but driving
at the same speed and how much energy is used. Changing the speed
is just obfuscation.



versus what was quoted but that doesn't
really matter since all we need is a reliable reference that backs up both
our intuition that the larger diameter setup will result in better fuel
economy.


"our" intuition again.


So far every reference I can find (e.g., Car & Driver & Cooper/Dunn Tire
and the Physics Forum) say that is not the case.

Wow, imagine that.