[RedDevil]

Originally Posted by Ecky

Maybe it does, maybe not. This isn't data I'm in possession of.

What I can say for certain is that rotating mass is a big deal whenever you have to change speed - 10 extra pounds of weight in your tires has a lot more impact on the amount of fuel it takes to get up to speed, and the amount of brake wear needed to slow you down, than 10lbs in the car. This is because the rotational inertia formula is mass times radius squared.

Or, in other words, tires with larger circumferences have exponentially more inertia than those with smaller diameters, while the rotating speed only goes up linearly. So, it's doubly important for this to get a light weight (narrow) tire if it has a larger circumferences. And for low pro tires, to keep the same wheel diameter they need to have larger diameter rims, so all of the weight of that metal is farther out, meaning exponentially more rotating mass again.

A narrower tire also has less aerodynamic drag, which is highly important at higher speeds.

Whatever the truth is about aspect ratio and width vs rolling resistance, the highest fuel economy cars have all had narrow, lightweight tires.

Sorry, but tire size has no effect on rotational inertia.
A taller tire has quadratically (not exponentially) more inertia for its bigger size, but the speed relation is also quadratical - and it rotates less fast than a smaller tire would for the same speed of the car, so these effects precisely cancel each other out.

Tire weight does increase inertia on a linear scale. Also it should be noted where the weight is; the thread adds twice its weight to the inertia as it is at the edge of the circle(*), the axle is just dead weight counting only once.

The biggest power loss from heavy wheels is caused by the suspension having to work harder. The lower the unsprung mass, the easier the wheels can track the road, the less the tire deforms on the bumps.

Taller tires also ride the bumps and troughs in the road surface more gently, which more than compensates for their generally heavier weight.

(*) Inertia of rotational mass.
It takes 1 Newton of force during 1 second to accelerate a mass of 1 kilogram to a speed of 1 meter per second.
During acceleration it moved half a meter, times 1 Newton means it took 0.5 Joule of energy to get it up to speed.

Now it does not matter whether that mass is moving straight on or in a circle. It just takes 0.5 Joule to get it to that speed.
A wheel is both rotating and moving forward at the same speed. So mass at the edge has to be spun up and moved as a whole; so that's twice the power needed.
It takes 1.0 Joule to speed up 1 kilogram of tire thread to a speed of 1 meter per second, half of it needed for spinning it up and the other half for getting it moving as a whole.